High-Intensity vs High-Volume Strength Training: A Scientific Comparison

body type workout guide Apr 23, 2025

Introduction

Strength training programs can vary widely in how intense or how voluminous they are. Intensity generally refers to the load or weight lifted (often expressed as a percentage of one’s one-repetition maximum, 1RM), whereas volume refers to the total amount of work done (sets × reps × weight, or simply total sets/reps). The debate over high-intensity vs high-volume training has raged for decades among athletes, coaches, and scientists ( A comparison of low volume 'high-intensity-training' and high volume traditional resistance training methods on muscular performance, body composition, and subjective assessments of training - PMC ). Both approaches can build muscle and strength, but they do so through different physiological pathways. In this article, we will define each training method, examine their underlying mechanisms, and compare their benefits and limitations. We’ll also review recent scientific studies (including meta-analyses) on each approach and discuss how they align with specific fitness goals such as hypertrophy, maximal strength, muscular endurance, athletic performance, and fat loss. Finally, we’ll provide practical guidelines on how to apply high-intensity or high-volume strategies based on individual goals.

Defining High-Intensity and High-Volume Training

High-Intensity Strength Training typically means lifting heavy weights relative to your maximum ability. In resistance training literature, “intensity” is usually defined as a percentage of 1RM. High-intensity training involves using very challenging loads (often ≥80% of 1RM) for low repetitions. For example, a classic high-intensity protocol might be 5 sets of 5 repetitions at ~85% of 1RM (Frontiers | Effects of High-Volume Versus High-Load Resistance Training on Skeletal Muscle Growth and Molecular Adaptations). Because the weight is heavy, the number of reps per set is low, and often fewer total sets are performed to avoid excessive fatigue. Some strength athletes and researchers also use the term “HIT” (High-Intensity Training) to describe a style of doing a low volume of sets but pushing each set to all-out effort (muscle failure). In practice, high-intensity training is characterized by maximal or near-maximal effort lifts, longer rest periods, and a primary focus on improving maximal force output.

High-Volume Strength Training, on the other hand, emphasizes doing a large quantity of work. This usually entails more sets and/or higher repetitions, typically with a more moderate load to allow for the greater volume. For example, a high-volume routine for the same exercise might be 5 sets of 10–12 repetitions at ~60–65% of 1RM (Frontiers | Effects of High-Volume Versus High-Load Resistance Training on Skeletal Muscle Growth and Molecular Adaptations). Here the weight per rep is lighter, but the total number of reps (and total weight lifted across the workout) is much higher. High-volume training is common in bodybuilding-style programs where multiple exercises, multiple sets, and moderate rep ranges are used to accumulate fatigue and metabolic stress in the muscles. Volume can be quantified weekly as well (e.g. number of sets per muscle group per week). Programs that prioritize volume often involve training a muscle with many sets (10+ sets per week in some cases) to maximize growth stimulus. In summary, high-volume training favors quantity of work over absolute load, while high-intensity training favors load (weight) over total repetition count.

( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ) Figure: The traditional "repetition continuum" concept in strength training illustrates how different rep ranges tend to target specific adaptations ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). Low-repetition, heavy load training (far left) falls in the strength zone, corresponding to high intensity efforts (e.g. 1–5 RM) that maximize neural and maximal strength adaptations. Moderate rep ranges (middle) are often called the hypertrophy zone (around 8–12 RM) and involve a mix of intensity and volume. High-repetition, lighter load training (far right, 15+ reps) falls in the endurance zone and represents high-volume approach, producing greater metabolic fatigue and muscular endurance adaptations. In reality, these zones overlap and muscle growth can be stimulated across a wide spectrum of loads, but the figure shows the classic framework linking intensity and volume to outcomes. ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC )

With these definitions in mind, let’s delve into the physiological mechanisms by which each approach elicits adaptations, and then compare their benefits and drawbacks.

High-Intensity Strength Training (Heavy Load, Low Volume)

High-intensity training is characterized by lifting heavy weights for relatively few repetitions. Physiologically, this places a premium on mechanical tension in the muscles and high-threshold motor unit recruitment. Because the loads are near maximal, the body responds with adaptations in the nervous system and muscle fibers to improve force production. Training with heavy loads (e.g. 1–5 RM range) quickly recruits the largest motor units (fast-twitch muscle fibers) to overcome the resistance. Over time, this leads to neurological adaptations such as improved motor unit recruitment, firing rate, and coordination between muscles. Research supports this: for example, one study found that training to failure at 80% 1RM elicited greater increases in voluntary muscle activation and EMG amplitude than training to failure at 30% 1RM over 6 weeks ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). In other words, heavy load training was more effective at training the nervous system to activate muscle fibers. High-intensity sets primarily stress the phosphagen (ATP-CP) energy system and create high force with relatively low cumulative fatigue per set, focusing the stimulus on myofibrillar hypertrophy (growth of the contractile proteins) and strength-related adaptations.

Benefits of High-Intensity Training: High-intensity strength training offers several clear benefits, especially for neuromuscular development and maximal strength:

Maximal Strength Gains: Lifting heavy is the most direct way to increase one’s 1RM strength. Meta-analyses show a clear advantage of heavy loads over light loads for improving 1RM strength when volume is held constant ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). In fact, training with loads >80% 1RM produces significantly greater strength increases than training with lighter loads (Physiological Responses and Adaptations to Lower Load ...) ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). Heavy training conditions the nervous system and muscles to generate high force, which is crucial for powerlifters and anyone seeking strength.
Neurological Efficiency: High-intensity work enhances neural drive and coordination. It “teaches” your body to synchronize muscle fibers and exert maximal effort. Studies have observed greater neural adaptations (e.g. motor unit activation) from heavy (e.g. 5RM) training than from high-rep training ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). This improved neuromuscular efficiency not only boosts strength but can also translate to better performance in explosive or high-power movements (since being able to rapidly recruit muscle fibers is key for power).
Muscle Preservation with Low Volume: Even with a low number of sets, heavy training can be effective at stimulating or preserving muscle mass. Because each heavy rep imposes high tension, a few sets might suffice to maintain muscle (useful in time-constrained programs). For example, brief “minimalist” routines using one set to failure with heavy weight (a style of HIT) have been shown to produce measurable strength and muscle gains in some studies ( A comparison of low volume 'high-intensity-training' and high volume traditional resistance training methods on muscular performance, body composition, and subjective assessments of training - PMC ). This makes high-intensity training quite time-efficient – a smaller volume of exercise can yield results when intensity is very high.
Bone Density and Connective Tissue: Lifting near-maximal weights places stress on bones, tendons, and ligaments, which can stimulate increases in bone mineral density and connective tissue strength over time. Heavy resistance is often recommended for improving bone health, particularly in older adults, because the high loads signal bones to remodel and become stronger (though this benefit is more of a general resistance training effect, heavy loads amplify it).

Limitations of High-Intensity Training: Despite its advantages, a pure high-intensity approach has some drawbacks and limitations to consider:

Limited Hypertrophy if Volume is Too Low: Muscle growth (hypertrophy) depends on both tension and sufficient training volume. If someone only does a few low-rep sets, the total stimulus for muscle growth may be insufficient. Research indicates that while heavy loads can induce hypertrophy, higher volumes tend to produce greater muscle size gains (Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis - PubMed). Thus, an exclusively high-intensity, low-volume regimen might not maximize hypertrophy compared to programs that incorporate more sets or reps. In practice, many strength athletes still include accessory exercises or additional sets to get enough volume for muscle growth.
Recovery Demands and CNS Fatigue: Lifting very heavy weights puts a lot of stress on the central nervous system and joints. High-intensity training usually requires longer rest periods between sets and more recovery days between sessions for the same muscle group. Continuously training at near-max loads without adequate recovery can lead to overtraining or injury risk. In fact, overtraining research shows that chronic high intensity (too high %1RM for too long) can induce excessive sympathetic stress and decreased performance (Overtraining: Undermining Success). Signs like joint pain, prolonged fatigue, or stagnation in strength could indicate that the nervous system or connective tissues are not recovering from the intensity.
Injury Risk with Heavy Loads: Because the weights are maximal, the margin for error in technique is smaller. Poor form or lack of proper progression under heavy loads can result in acute injuries (muscle tears, tendon strains, etc.) or chronic joint stress. This doesn’t mean high-intensity training is unsafe – only that it requires good exercise technique, warm-up, and sensible programming. Beginners, in particular, must be cautious when handling very heavy weight to avoid injury.
Narrow Focus (Strength over Endurance): High-intensity, low-rep training builds strength and power, but it does relatively little for muscular endurance or cardiovascular fitness. If one’s fitness goals require sustaining submaximal force for many repetitions or improving metabolic conditioning, heavy-low rep training alone won’t be sufficient. The adaptations are very specific: you get better at lifting heavy for short bursts, not at prolonged exercise. Athletes often need to complement high-intensity work with other training to cover endurance or conditioning needs.

In summary, high-intensity strength training is a potent tool for boosting maximal strength and neuromuscular performance, but it must be programmed with care. Typically, it’s best combined with adequate rest and, often, some volume work to ensure balanced development. This is where high-volume training comes in as a complementary approach.

High-Volume Strength Training (Multiple Sets, Moderate Load)

High-volume training centers on doing a large amount of total work. This means more sets, more repetitions, or both. The loads per set are usually moderate (or even light) to allow the lifter to complete high rep counts and multiple sets without hitting failure too quickly. Physiologically, high-volume training induces adaptations through accumulated fatigue, metabolic stress, and longer time-under-tension for muscles. While each rep might carry less absolute tension than a heavy lift, the cumulative effect of many reps is significant. Muscles experience greater metabolic stress (accumulation of lactate, hydrogen ions, and other metabolites) and often muscle damage from the extended work, which are stimuli that can contribute to muscle growth. This style of training tends to engage not just the largest motor units, but also heavily taxes the more endurance-oriented muscle fibers (Type I fibers) because they must sustain activity over many repetitions.

Mechanistically, high-volume workouts create a robust hormonal and molecular response: they often lead to higher acute spikes in anabolic hormones (like growth hormone) post-exercise, although the role of these transient hormone changes in hypertrophy is debated ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ) ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). More concretely, performing lots of sets triggers muscle protein synthesis pathways via both mechanical tension (repeated often) and metabolic signals. Some research suggests that higher-volume sessions may preferentially increase certain elements of muscle tissue, such as sarcoplasmic proteins (the non-contractile components like glycogen and enzymes) leading to a form of “sarcoplasmic hypertrophy” – an increase in muscle size not solely due to bigger contractile fibers (Frontiers | Effects of High-Volume Versus High-Load Resistance Training on Skeletal Muscle Growth and Molecular Adaptations). In simpler terms, high reps can increase the muscle’s endurance capacity and storage (glycogen, capillaries) alongside muscle size. High-volume training also conditions the muscle to better resist fatigue. The longer time-under-tension and metabolite accumulation can stimulate adaptations like improved buffering capacity and mitochondrial density in muscle cells ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ), which is why this approach excels at improving local muscular endurance.

Benefits of High-Volume Training: A high-volume approach offers several advantages, particularly for muscle development and endurance:

Enhanced Muscle Hypertrophy: Volume is a key driver of hypertrophy. Numerous studies and reviews have found a dose-response relationship between training volume and muscle growth (Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis - PubMed) (Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis - PubMed). Essentially, doing more sets (up to a point) leads to greater increases in muscle size. One meta-analysis quantified that each additional set per week is associated with about a 0.37% increase in muscle cross-sectional area on average (Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis - PubMed). Comparisons of training volumes show that programs with higher weekly set counts (e.g. >10 sets per muscle group) yield significantly more muscle growth than lower-volume programs (Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis - PubMed) (Frontiers | Resistance Training Variables for Optimization of Muscle Hypertrophy: An Umbrella Review). High-volume training provides a broad stimulus (mechanical tension spread over many repetitions plus metabolic stress) that maximizes hypertrophic signaling in the muscle. This is one reason bodybuilders traditionally favor multiple exercises and sets – to ensure the muscle is thoroughly fatigued and stimulated for growth.
Improved Muscular Endurance and Work Capacity: By performing many repetitions, high-volume training specifically targets the muscle’s ability to sustain force output over time. High-rep, light-to-moderate load training optimizes local muscular endurance adaptations ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). Trainees experience an increase in their ability to tolerate and clear lactate, delay fatigue, and perform more work before exhaustion ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). For example, doing 3–4 sets of 15-20 reps will train a muscle to handle extended activity much better than 3 sets of 3 reps would. This improved endurance can benefit activities that require repeated efforts (e.g. high-volume training can help a cyclist grind up a long hill or a wrestler perform numerous explosive moves throughout a match). It also raises overall work capacity, meaning an individual can handle more total training workload over time.
Greater Caloric Expenditure: High-volume sessions typically burn more calories during the workout compared to low-volume heavy sessions, simply because more total work is being done. If you perform 5 sets of 10 versus 3 sets of 3, you have lifted the weight many more times. This higher energy expenditure can contribute to fat loss or improved body composition when combined with a proper diet. Additionally, the high metabolic stress can elevate post-exercise oxygen consumption (EPOC) slightly, meaning your body continues to use extra energy after the session to recover. While diet remains the key for fat loss, the caloric burn from volume training is a helpful factor (and we’ll discuss later how volume plays a role in preserving muscle during fat loss).
Comprehensive Muscle Stimulation: High-volume training often involves hitting the muscle from multiple angles or with various exercises in the same session. This can lead to more uniform development. For example, a high-volume leg workout might include squats, lunges, leg presses, and hamstring curls, each for multiple sets. This thorough approach can ensure that all fibers in a muscle are fatigued. Even within a single set, doing, say, 12 reps will recruit additional fibers toward the end of the set as fatigue sets in (eventually engaging high-threshold fibers as one nears failure, even with lighter weight). In fact, when sets are taken near volitional failure, even low-load sets can recruit the full spectrum of muscle fibers by the final reps ( Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis - PMC ) ( Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis - PMC ). Thus, volume training (especially to fatigue) can achieve broad muscle fiber recruitment similar to heavy training, albeit via cumulative fatigue rather than instant high tension.
Skill Practice and Technique: With more total repetitions, lifters get more practice performing the exercises, which can help reinforce technique (at least at moderate loads). For complex lifts, doing multiple sets of 8–12 reps provides a lot of motor practice, potentially improving form and neural patterns. (One caveat: as fatigue sets in, technique can degrade, so it’s important to maintain good form even during high rep sets.)

Limitations of High-Volume Training: High-volume regimens, while effective for hypertrophy and endurance, come with their own set of challenges and downsides:

Time and Energy Demanding: Simply put, doing a lot of sets and reps takes time. High-volume workouts tend to be longer in duration, which can be a practical limitation for those with busy schedules. They are also very fatiguing. Performing many sets to near failure can leave one exhausted and sore. Not everyone can tolerate extremely high volumes, especially without gradually building up to it. There’s also a mental component – high-volume training requires grit and motivation to push through repetitive, often painful last reps (the “burn” of high reps). This can be tough to sustain long-term for some individuals.
Risk of Overtraining or Overuse: When volume is too high or recovery is insufficient, athletes may experience overtraining symptoms. Chronically high training volume can cause a disproportionate stress response: for instance, very high volume has been linked to decreases in the testosterone-to-cortisol ratio, indicating a shift toward a catabolic (muscle-breaking) state (Overtraining: Undermining Success). Without deloads or proper nutrition and rest, excessive volume could impair progress. Overuse injuries (like tendinitis or stress fractures) are also a concern if high volume is achieved through very high frequency of training or repetitive movements without rest. Joints and connective tissues need time to recover from the cumulative micro-trauma of lots of reps. Therefore, moderation and progressive overload are key – one shouldn’t jump from low volume to extremely high volume suddenly.
Diminishing Returns After a Point: There is an optimal volume range for each individual. Doing more sets beyond that doesn’t always yield proportional benefits. For example, if someone is already doing 15 sets for a muscle group per week, jumping to 30 sets may not double the gains – in fact, it might just increase fatigue with minimal extra hypertrophy (“junk volume”). Scientific evidence suggests a threshold around 8–12+ sets per muscle per week for most people to maximize growth, with returns tapering off beyond that (Frontiers | Resistance Training Variables for Optimization of Muscle Hypertrophy: An Umbrella Review). Very high volume can also interfere with intensity – if you try to do both high volume and relatively heavy weight, you might end up too exhausted to put quality effort into later sets. Thus, balancing volume with intensity is important; all-out high volume can compromise the quality of each rep due to fatigue.
Less Emphasis on Max Strength: If training is mostly high rep, moderate load, one might see limited improvements in 1RM or maximal strength. As discussed, strength gains are quite load-specific. While high-volume training will increase muscle size (which indirectly can increase potential strength), it may not train the neuromuscular system for peak force production. In practice, athletes focusing only on 10-15 rep sets might find when they attempt a 1RM lift, they lack the neural adaptation to express their strength fully. High-volume programs often need to be cycled with some heavier work to translate hypertrophy into maximal strength.
Pump and Fatigue ≠ Progressive Overload by themselves: High-volume bodybuilding-style training often produces a great muscle “pump” and soreness, which many associate with effectiveness. However, it’s important to ensure that volume is increased progressively and paired with attempts to gradually use more weight or more reps over time. Simply doing a ton of volume with light weight without progressive overload will eventually plateau. The limitation here is that chasing volume for its own sake can lead to sloppy form or insufficient intensity per set. Each set still needs to challenge the muscle sufficiently (usually close to failure) to be effective ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ) ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). Volume is a tool, not an excuse for using trivial weights – one must find a balance so that the high volume consists of effective work.

In summary, high-volume training is a proven strategy for muscle growth and endurance improvements, but it requires significant time and recovery capacity. It’s particularly useful for bodybuilding goals and for improving muscular stamina, but should be programmed wisely to avoid overtaxing the body. Many successful programs integrate both high-volume and high-intensity elements, periodizing them to capitalize on the benefits of each while mitigating the downsides.

High-Intensity vs High-Volume for Different Fitness Goals

Now that we’ve examined each training style in general, how do they stack up for specific goals? The optimal approach can differ depending on whether your priority is muscle size, pure strength, endurance, athletic performance, or fat loss. Below, we discuss each goal and how high-intensity and high-volume training align with them, backed by scientific findings:

Muscle Hypertrophy (Muscle Size)

If your primary goal is to increase muscle mass, evidence suggests that a higher-volume approach is generally more effective. Muscle hypertrophy has been shown to respond in a dose-dependent manner to training volume: more sets can produce greater growth, up to an individual’s recoverable limit (Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis - PubMed). For example, a systematic review and meta-analysis found that programs with higher weekly set volumes led to significantly more muscle growth than lower volume programs, with ~10+ sets per muscle per week needed to maximize hypertrophy in many cases (Frontiers | Resistance Training Variables for Optimization of Muscle Hypertrophy: An Umbrella Review). High-volume training provides more total stimulus (mechanical loading and metabolic stress), which encourages muscles to grow bigger.

Interestingly, the intensity (load) used can be quite flexible for hypertrophy, as long as the sets are taken near muscle failure. Research indicates that both heavy loads and lighter loads can induce similar hypertrophy when volume and effort are matched ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ) ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). For instance, studies have compared low-rep (~3-5 reps) high load training versus high-rep (20+ reps) low load training and found no significant difference in muscle growth provided the lighter-load groups went to failure to recruit all fibers ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). One meta-analysis concluded that muscle hypertrophy improvements are essentially load-independent across a wide range (30% to 80% 1RM) so long as you train with a high level of effort (i.e., close to failure) ( Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis - PMC ). What this means in practical terms is that you can grow muscle with heavy weights or light weights – but you must do enough total work. High-volume training typically satisfies that requirement by increasing the number of challenging sets.

That said, there are some nuances. Moderate rep ranges (6–12 reps) have traditionally been dubbed the “hypertrophy range” because they allow a balance of intensity and volume. Lifting very heavy for very low reps might require so many sets to get adequate volume that it’s impractical for hypertrophy, whereas very light for 50 reps, even taken to failure, might cause more discomfort than necessary. Most bodybuilders gravitate to moderate loads where they can accumulate volume with good form. This aligns with the classic hypertrophy zone around 60–80% 1RM ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). At these loads, one can typically do enough sets and reps to maximize growth without excessive joint strain.

Scientific support: Multiple studies reinforce the importance of volume for hypertrophy. As mentioned, Schoenfeld et al. (2017) found a graded relationship where each additional set per muscle group correlated with further muscle size gains (diminishing returns after a point) (Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis - PubMed). Another meta-analysis by Schoenfeld and colleagues reported no hypertrophy advantage to using heavy loads over light loads if sets were taken to failure – both produced similar muscle thickness increases ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). And a recent experiment by McDonald et al. (2022) showed that in trained lifters, a high-volume protocol (~10–12 rep sets) led to a +3.2% increase in muscle cross-sectional area of the quadriceps, whereas a high-intensity (heavy load, ~5 rep) protocol did not significantly increase CSA over 6 weeks (Frontiers | Effects of High-Volume Versus High-Load Resistance Training on Skeletal Muscle Growth and Molecular Adaptations) (Frontiers | Effects of High-Volume Versus High-Load Resistance Training on Skeletal Muscle Growth and Molecular Adaptations). Notably, in that study the high-intensity leg got stronger (as expected), but the high-volume leg grew bigger. This perfectly exemplifies the strength vs size trade-off when choosing intensity vs volume.

Implications for training: To maximize hypertrophy, emphasize volume: multiple exercises, multiple sets per muscle group, and train each muscle roughly 10–20 total sets per week (exact optimal volume varies per individual) (Frontiers | Resistance Training Variables for Optimization of Muscle Hypertrophy: An Umbrella Review). Use moderate loads that allow you to get at least ~6–12 reps per set so you can rack up enough time-under-tension. High-intensity sets (e.g. 3-5 reps) can still be included – they will certainly recruit muscle fibers – but you will likely need additional sets or accessory work to accumulate the training volume necessary for maximal growth. Many successful bodybuilding routines pair heavy compound lifts (for a few sets) with additional moderate rep sets of isolation or accessory lifts to combine intensity and volume. The bottom line: for muscle size, volume is king, so a high-volume training strategy (possibly combined with some heavy lifting) is the most direct route to hypertrophy. Ensure you progressively overload by adding either weight or reps over time, and eat enough protein and calories to support growth.

Maximal Strength

To maximize pure strength (the highest load you can lift for 1 rep), high-intensity training is indispensable. Getting stronger, especially for low-rep max efforts, is highly specific to lifting heavy weights. Heavy load training (at or above ~85% of 1RM) yields superior gains in 1RM strength compared to lighter load training (Physiological Responses and Adaptations to Lower Load ...) ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). This has been demonstrated in numerous studies. For example, one meta-analysis found a moderate-to-large effect size advantage for high-load (>60% 1RM) training over low-load (<60% 1RM) training on 1RM strength gains ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). All studies in that analysis showed heavier loads produced greater strength improvements, confirming the principle of specificity: to lift heavier, you must train heavier.

High-intensity training improves neuromuscular factors critical for strength: motor unit recruitment, intermuscular coordination, and neural drive. Practicing lifts with near-maximal weights teaches your body to handle those loads efficiently. There’s also a psychological component – regularly lifting heavy accustoms you to the strain of max efforts, reducing mental inhibition when attempting big lifts ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). Lighter, high-volume training simply cannot replicate these effects, because if you never lift above, say, 60% of your max, your nervous system isn’t being challenged to fire at 100% capacity.

That said, volume still has a role in strength training: doing more sets of heavy work will produce more strength gain than doing just a few sets. In fact, volume can be a driver of strength gains provided intensity is kept high. A meta-analysis on strength gain found that higher weekly set volumes (5+ sets per muscle) led to larger strength increases than low volume (≤4 sets), even when using relatively heavy loads (Strength: Systematic Review And Meta-Analysis Master List). So a powerlifter, for example, will squat heavy to get stronger, but might squat heavy for multiple sets across the week (“volume day” vs “intensity day” in some programs). Essentially, you need enough heavy lifting practice to maximize strength.

Scientific support: Beyond the meta-analyses already noted, consider the study by Schoenfeld et al. (2014) which compared 8 weeks of training in trained men using either very heavy loads (2–4 RM) or moderate loads (8–12 RM). The heavy-load group saw greater 1RM strength gains than the moderate group, as expected, but interestingly both groups saw hypertrophy gains (with a slight edge to the moderate group’s muscle size) ( Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis - PMC ) ( Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis - PMC ). This illustrates that for strength, the heavier the better (the moderate load group did get stronger too, just not as much), whereas hypertrophy can be obtained across intensities. Another piece of evidence in athletes: heavy strength training (with or without plyometrics) has been shown to improve performance metrics such as sprint speed and jump power in trained individuals, whereas training with light loads has less effect on maximal power output (Heavy strength training and plyometric improves running economy ...). This is relevant because maximal strength underpins explosive power – increase your strength ceiling with heavy training, and your power potential increases.

Implications for training: For maximal strength development, prioritize high-intensity training: lift heavy weights in the 1–6 rep range for multiple sets. Focus on compound movements that allow heavy loads (squats, deadlifts, presses, pulls, etc.). Incorporate adequate rest between sets (2–5 minutes) to allow near-full recovery so each heavy attempt is high quality. While some accessory volume work can be included, it should not replace heavy sets. A practical approach is to perform your main lifts in a heavy low-rep scheme (e.g. 5x5, 4x4, or working up to heavy triples or singles), then optionally do a few back-off sets or accessory exercises for additional volume. This way, you get the neurological stimulus of heavy lifting and enough total work to drive adaptation. Periodization is often used: for example, a cycle might start with slightly higher volume at moderately heavy loads, then progressively peak to lower volume at very high loads as you approach a strength max test. The key is that at every stage, the intensity is relatively high (certainly ≥70–80% 1RM, often 85%+ for true strength phases). High-volume, low-load training on its own will not maximize your 1RM, though it can build muscle that later can be “converted” to strength with heavier training. Thus, high-intensity training is the cornerstone for maximal strength gains, with volume playing a supportive secondary role.

Muscular Endurance

For muscular endurance (the ability of a muscle to perform repeated contractions or to sustain a contraction over time), high-volume (high-rep) training is unquestionably the appropriate tool. Improving local muscular endurance means training the muscle to resist fatigue and clear metabolites efficiently during extended efforts. This is achieved by doing a high number of repetitions, typically in the range of 15+ reps per set with light to moderate weight ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). Such training falls on the far right of the repetition continuum (endurance zone). It induces specific adaptations: increased mitochondrial density in muscle fibers, greater capillarization, and enhanced metabolic enzyme activity that collectively improve the muscle’s fatigue resistance.

Research and guidelines consistently show that performing sets of 15–25+ reps with short rest intervals is optimal to improve muscular endurance ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ) ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). In contrast, low-rep, high-intensity training does little to push the endurance capacity because the sets are too brief to tax the relevant energy systems (glycolytic and oxidative pathways). Think of a powerlifter vs. a rower: the powerlifter can move huge weight once (strength) but the rower can sustain a moderate force for thousands of strokes. To build endurance, the rower must train with volume.

Scientific support: The physiological reasoning is well documented. High-repetition training leads to greater accumulation of lactic acid and a more hypoxic intramuscular environment, which in turn triggers adaptations for buffering acidity and improving oxygen delivery. One review noted that muscular endurance is best developed with at least 15+ reps per set, as this protocol preferentially challenges Type I (slow-twitch) fibers and evokes improvements in their aerobic capacity ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). In the earlier-cited MDPI review, the authors point out that training at the rightward end (high reps) of the spectrum yields specific endurance adaptations such as improved buffering of metabolites and increased oxidative enzymes ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). High-volume circuit training or drop-set training can further amplify these effects by combining lots of reps with minimal rest, forcing the muscle to continue working under fatigue.

In practical studies, when groups train with high reps vs low reps, the high-rep group excels in tests of muscular endurance. For example, a classic 1982 study by Anderson & Kearney had subjects train with different rep ranges; the high-rep group showed superior endurance (measured by the number of reps they could do at a submax load) compared to the low-rep, heavy group – even if their max strength was lower. This is a demonstration of specificity: endurance training yields endurance improvements.

Implications for training: To increase local muscular endurance, adopt a high-volume training strategy: perform sets of 15-20+ repetitions, use relatively short rest periods (30 seconds to 1 minute is common in endurance-focused lifting), and perhaps incorporate techniques like supersets or circuits to keep the muscle working with minimal rest. The weight used will be light relative to your max (likely 40-60% 1RM or even just bodyweight for some exercises), but the challenge comes from the high rep count. It’s important to reach a point of fatigue in those high-rep sets (without necessarily going to absolute failure every time, which can be very uncomfortable at 20+ reps). You should feel the "burn" – that indicates you are taxing the endurance mechanisms. An example protocol for muscular endurance in the upper body might be 3 sets of 20 push-ups with 30 seconds rest, or lower body might be 2–3 sets of 25 bodyweight squats, etc., progressively increasing reps over time.

While high-intensity training is not needed to improve endurance, some integration can be useful: maintaining a bit of heavy lifting in your program (even as low as 1 day a week) can preserve strength so that your endurance sets become easier in terms of percentage of your max. But the majority of training for an endurance goal should be high volume. High-volume training is perfectly aligned with muscular endurance development, as it conditions the muscle’s metabolic efficiency and fatigue resistance.

Athletic Performance

When it comes to athletic performance, the ideal mix of high-intensity vs high-volume training depends on the sport and the specific performance needs. “Athletic performance” is a broad term – a powerlifter’s performance is pure strength, a marathoner’s is pure endurance, and many sports require a blend of strength, power, speed, and endurance. Therefore, both training modalities have important roles, and periodizing both high-intensity and high-volume phases is common in athletic training.

For strength and power athletes (e.g. Olympic weightlifters, sprinters, throwers, football linemen), high-intensity strength training is crucial. These athletes need to generate maximal or near-maximal force in their sport skills. Heavy lifting improves their neural drive, rate of force development, and overall strength, which translates to better performance (e.g. a sprinter benefiting from stronger legs for push-off, or a thrower from a stronger upper body). In addition, heavy resistance training can improve qualities like tendon stiffness and intermuscular coordination that enhance explosive movements. There’s evidence that even endurance athletes benefit from some heavy training: for instance, a systematic review and meta-analysis on runners found that adding heavy strength training (≥80% 1RM) improved running economy (the energy cost of running) and improved performance at higher speeds ( Effect of Strength Training Programs in Middle- and Long-Distance Runners’ Economy at Different Running Speeds: A Systematic Review with Meta-analysis - PMC ). The runners who lifted heavy could run the same speed with less effort, presumably due to increased muscle strength and improved neuromuscular efficiency. Lighter, high-rep training did not significantly improve running economy in those studies ( Effect of Strength Training Programs in Middle- and Long-Distance Runners’ Economy at Different Running Speeds: A Systematic Review with Meta-analysis - PMC ). Similarly, heavy strength training plus plyometrics has been shown to improve jump height and sprint time in team sport athletes, whereas just doing conditioning without heavy lifts yields smaller gains.

On the other hand, many sports also demand muscular endurance or hypertrophy, where high-volume training contributes. For example, a soccer player or MMA fighter might do high-volume circuit training to improve muscular endurance and fatigue resistance, allowing them to perform repeated efforts throughout a long match. Athletes in contact sports (rugby, American football) often do hypertrophy-oriented high-volume training in the off-season to build muscle mass and size, which can be advantageous for collision sports. That added muscle (acquired via volume training) can then be “activated” in the preseason by switching to heavier, high-intensity work to convert the new muscle into maximal strength and power. In endurance sports (distance running, cycling, swimming), the majority of sport-specific training is of course high-volume endurance work. But supplementary strength training is still recommended: typically a mix of heavy low-rep strength exercises for economy and some moderate rep exercises for injury prevention and muscular balance.

In essence, athletes periodize: using high-volume phases to build general capacity, muscle size, or endurance, and high-intensity phases to maximize strength, power, and neural readiness closer to competition (Overtraining: Undermining Success) (Overtraining: Undermining Success). Too much volume in season can make an athlete sluggish or excessively fatigued, whereas too much intensity year-round can burn them out or risk injury. So the balance is key.

Scientific support: The running economy example given above is a strong testament to heavy training for performance – “Strength training with high loads (≥ 80% 1RM) can improve running economy and is particularly effective for well-trained runners” ( Effect of Strength Training Programs in Middle- and Long-Distance Runners’ Economy at Different Running Speeds: A Systematic Review with Meta-analysis - PMC ). Another example: a study on collegiate throwers found that those who engaged in a periodized program with a hypertrophy phase (high volume) followed by a max strength phase (high intensity) and then a power phase had better performance outcomes than those who did random training. The high-volume phase built a base of muscle and work capacity, the high-intensity phase increased neural strength, and the final phase translated it into sport-specific power. This model of periodization (accumulation → intensification → realization) is common in athletics (Overtraining: Undermining Success).

Implications for training: If you are an athlete, consider what your sport demands:

For Strength/Power: Emphasize high-intensity training. Include heavy compound lifts for low reps to develop raw strength. Also incorporate explosive training (plyometrics, Olympic lifts) which often involves moving moderate loads quickly – another form of intensity. Keep some volume in the program but not so much that it impairs recovery for high-intensity work. In-season, volume is usually reduced to allow more focus on skill practice and maintaining intensity.
For Hypertrophy/Size (if needed): Use high-volume blocks, typically in off-season, to add muscle mass. Bodybuilding-style training can be beneficial for increasing cross-sectional area of muscles, which can increase potential force (larger muscle can become stronger muscle after neural training). Just be mindful to not carry excessive fatigue into skill workouts.
For Endurance within the Muscle: If your sport requires repeated contractions (e.g., rowing, wrestling), include some high-rep resistance training or circuit training to boost muscular endurance. This could be things like doing 30-rep squats for a rower, or a circuit of push-ups/pull-ups for a rock climber, etc. These high-volume workouts should mimic the demands of the sport in terms of energy system.
Integrated Approach: Most sports will benefit from a combination. For example, a basketball player might lift heavy (squats, deadlifts) to improve jump power (intensity), do moderate rep work for hypertrophy of key muscles, and also do conditioning circuits or bodyweight high-rep work for muscular endurance (since games are long). Organizing training into cycles ensures the athlete is not trying to maximize all qualities at once, which can be conflicting.

In summary, athletic performance is best served by a strategic blend of high-intensity and high-volume training. High-intensity work underpins improvements in maximal strength and explosive power, which are critical for most sports, while appropriate doses of high-volume training build the necessary muscle mass and endurance. Athletes should tailor the ratio of intensity to volume based on their sport and even their position or event, and adjust throughout the season.

Fat Loss (Cutting Body Fat while Preserving Muscle)

During a fat loss phase (caloric deficit), the goal of resistance training is a bit unique: you want to maximize fat loss (mainly driven by diet) while preserving lean muscle mass and strength. Both high-intensity and high-volume training can play a role here, and the optimal approach often combines elements of both.

To prevent muscle loss when in a calorie deficit, it’s crucial to continue providing the muscle with a strong growth/maintenance stimulus. Heavy, high-intensity training is important for preserving strength and reminding the body to keep the muscle (use it or lose it). If you stop lifting heavy during a diet, your muscles might atrophy and your strength will drop. So one aspect is to keep lifting relatively heavy weights for low-to-moderate reps, to maintain neural adaptations and muscle fiber recruitment. This signals to your body that the muscle is still needed.

At the same time, overall training volume should be sufficient to maintain muscle protein synthesis and hypertrophic signaling. Interestingly, some research suggests that dropping training volume significantly during a diet can lead to more muscle loss, whereas maintaining or even slightly increasing volume (if recovery allows) helps preserve lean mass ( Sciences of Sport | Losing body fat while maintaining muscle mass: The role of training volume ) ( Sciences of Sport | Losing body fat while maintaining muscle mass: The role of training volume ). A review of studies on bodybuilders and athletes in contest prep noted that those who kept training volume high (≥10 sets per muscle per week) were able to maintain or even gain a small amount of muscle, while those who reduced volume lost muscle ( Sciences of Sport | Losing body fat while maintaining muscle mass: The role of training volume ) ( Sciences of Sport | Losing body fat while maintaining muscle mass: The role of training volume ). The rationale is that volume is a key driver of muscle mass; in a deficit, the threshold to just hold onto muscle might be higher (since your body is in a catabolic state, you need to fight that with enough training stimulus).

Of course, a caloric deficit impairs recovery to some extent, so one cannot simply double the volume – it’s a balancing act. Often, bodybuilders will keep training intensity fairly high (still lift heavy in moderate rep ranges) and keep a moderate volume, rather than extremely high, to avoid excessive fatigue. They might incorporate some higher-rep, short rest “metabolic” work as well, which can burn extra calories and induce a good muscle pump (which some believe helps retain muscle by increasing nutrient delivery, though that’s anecdotal). Essentially, in fat loss training, the priority is muscle retention first, calorie burning second. Resistance training itself does not burn as many calories as cardio, but it is indispensable for preserving muscle while you lose fat.

Scientific support: The science on fat loss and resistance training consistently shows that combining diet with strength training preserves more lean mass than diet alone. The question of high-intensity vs high-volume within that is less studied, but the review from Sci-Sport we referenced analyzed multiple studies: They found that in contexts where protein was high and calories restricted, those who had moderate-to-high training volumes tended to keep more muscle (or even gain a bit) compared to those who had low volume ( Sciences of Sport | Losing body fat while maintaining muscle mass: The role of training volume ). For example, in studies with female athletes, those doing around 10–20 sets per muscle weekly during a cut often maintained muscle, whereas those dropping below 5 sets lost muscle ( Sciences of Sport | Losing body fat while maintaining muscle mass: The role of training volume ). In male studies, muscle loss was more common (men tend to lose muscle easier when dieting hard), but the only ones that maintained muscle had actually increased training volume during the diet ( Sciences of Sport | Losing body fat while maintaining muscle mass: The role of training volume ). This suggests that adequate volume is crucial to counteract the catabolic effect of dieting. Another reason volume helps is it may offset the reduction in training-induced muscle protein synthesis that occurs when energy is low – by doing more sets, you might prolong the MPS signal even if each individual response is blunted.

Meanwhile, heavy-intensity training ensures that strength is maintained. Anecdotally and logically, if you continue to lift close to your normal heavy weights while losing fat (even if you can do fewer reps with it), you stand a better chance of retaining muscle fibers. If you were to switch entirely to just light weight high reps during a cut (and drop heavy work), you might lose some of your top-end strength and Type II fiber size. So a mix is often recommended: lift heavy to keep strength, and do enough volume to safeguard muscle size.

Implications for training: In a fat loss phase, you might combine approaches: For example, you could perform your main lifts in a heavy, low-rep style (to maintain strength and muscle fiber recruitment), then add a couple higher-rep accessory or drop sets to increase volume and calorie expenditure. Keep the total volume at least moderate (don’t fall to a “minimal” routine) – many coaches advise trying to train with similar volume as in muscle-building phases, if recovery permits, just maybe not pushing to PRs in weight. You likely shouldn’t drastically ramp up volume either, since you have less recovery capacity. The key is to find a sustainable volume that provides enough stimulus.

Practically, one might train each muscle ~2 times a week with moderate volume, using a mix of rep ranges. High-volume metabolic workouts (like circuits or supersets with little rest) can be sprinkled in to burn extra calories and improve conditioning, but these shouldn’t replace heavy lifting altogether. Also, maintain a high protein diet to support recovery. The data implies it’s “preferable to increase training volume or keep it high during calorie restriction” for muscle retention ( Sciences of Sport | Losing body fat while maintaining muscle mass: The role of training volume ), so don’t cut back your lifting sessions just because you are doing cardio or eating less – your muscles need the work to stick around.

In summary, for fat loss: use both heavy and volume. High-intensity training will preserve strength and muscle density, while high-volume work will ensure an ongoing hypertrophy stimulus and burn some calories. Together, they help you lose mostly fat while keeping that hard-earned muscle. Always listen to your body, though – if recovery falters, you may need to adjust frequency or volume to avoid overtraining in a caloric deficit.

Practical Guidelines and Takeaways

To apply these concepts to your own training, consider your primary goal and design your program to emphasize either high-intensity or high-volume accordingly (often including elements of both). Below are practical guidelines based on individual goals:

If your goal is maximal strength: Prioritize high-intensity training. Center your routine on heavy compound lifts in the 1–5 rep range, using ~80–100% of your 1RM for multiple sets ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). Ensure long rest periods for full recovery between sets. Include some additional sets (5+ sets per muscle per week) to reinforce strength gains (Strength: Systematic Review And Meta-Analysis Master List), but avoid excessive volume that could dilute intensity. Focus on progressive overload in weight lifted. For example, a powerlifting-style program with low-rep heavy sets and a moderate number of total sets is ideal.
If your goal is muscle hypertrophy: Emphasize high-volume training to accumulate sufficient stimulus. Train each muscle group with at least ~10 sets per week (or more, depending on your recovery) (Frontiers | Resistance Training Variables for Optimization of Muscle Hypertrophy: An Umbrella Review). Use mainly moderate loads (60–80% 1RM) for 6–15 reps per set, and go near muscle failure on those sets for maximal fiber recruitment. Incorporate multiple exercises per muscle to ensure complete development. You can still include some heavy low-rep sets, but most of your training should be in higher rep ranges to maximize time-under-tension and metabolic stress. Track your total volume and aim to gradually increase reps or sets over time (while maintaining good form and effort).
If your goal is muscular endurance: Adopt a high-repetition, high-volume approach. Use lighter weights (below ~60% 1RM) and perform sets of 15–25+ reps ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). Keep rest intervals short (30–90 seconds) to train the muscle to recover quickly. Circuit training or supersets can be useful to target endurance in multiple muscle groups. Focus on sustaining good form under fatigue. For example, you might do 3 sets of 20 reps on several exercises. This will enhance the muscle’s fatigue resistance and metabolic efficiency ( Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum - PMC ). Heavy lifting can be kept minimal (or done occasionally) in this phase, as the primary aim is to increase repetition capacity, not 1RM strength.
If your goal is athletic performance: Blend high-intensity and high-volume training in a periodized manner. First, identify the primary qualities your sport needs (strength, power, size, endurance). In general, include heavy, explosive lifts to develop strength and power (especially for athletes in speed, power, or team sports) and use volume strategically for hypertrophy or muscular endurance as needed. For example, in off-season you might do a hypertrophy block (higher volume) to build muscle, then transition to a strength/power block (higher intensity) as the season approaches (Overtraining: Undermining Success). Endurance athletes should do heavy strength training 1–2 times per week to improve economy ( Effect of Strength Training Programs in Middle- and Long-Distance Runners’ Economy at Different Running Speeds: A Systematic Review with Meta-analysis - PMC ), but keep most sport-specific training high-volume. Team sport athletes can mix heavy lifting days with conditioning circuits. Always align your training block with your sport’s demands – e.g., don’t do an extremely high-volume leg workout the day before a speed training session. Periodization helps manage fatigue: higher volume further from competition, higher intensity when nearing competition.
If your goal is fat loss (while preserving muscle): Combine moderately heavy lifting with sufficient volume. Keep lifting weights in the moderate rep range (5–12 reps) with some heavy sets to maintain strength and muscle tension. At the same time, do enough total sets for each muscle weekly (often similar to your muscle-building routine, if possible) to signal the body to keep its muscle ( Sciences of Sport | Losing body fat while maintaining muscle mass: The role of training volume ) ( Sciences of Sport | Losing body fat while maintaining muscle mass: The role of training volume ). You can incorporate some high-volume metabolic work (e.g. finishing a workout with a high-rep burnout set or doing weight training in a circuit fashion) to increase calorie burn, but not at the expense of heavy work. Essentially, don’t drastically cut training volume during a cut – many experts advise trying to train with the same frequency and volume, just be mindful of recovery. Ensure a high protein intake to aid recovery. An example fat-loss training week might involve full-body workouts with a heavy compound lift first (3×5 reps), followed by accessory supersets at 10–15 reps to get a pump and additional volume. This approach will help maximize fat loss while minimizing muscle loss by leveraging both intensity and volume.

Remember that individual responses vary – some people thrive on high intensity, others on high volume. It’s important to adjust according to how your body responds and recovers. Often, the best practice is a combination: use high intensity for what it does best (strength, neural adaptation) and high volume for what it does best (hypertrophy, endurance), cycling or mixing them in your program. Both methods are tools in your toolbox. By understanding their mechanisms and effects, you can intelligently design a training regimen that best fits your goals, backed by scientific evidence and principles of exercise physiology. Keep tracking progress and listening to your body, and you can fine-tune the balance of intensity and volume to continually make gains toward your fitness objectives.

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