What is muscle strength?
Muscle strength refers to the ability to produce force against an external resistance.[8] It is often divided into specific types of strength, such as lower body strength or upper body strength.
How is muscle strength measured?
Strength is commonly assessed using dynamic resistance exercise,[9] which includes concentric (muscle shortening) and eccentric (muscle lengthening) muscle actions. The most popular method is a 1-repetition maximum (1RM) test,[10] which involves lifting as much weight as possible for one repetition using either free weights or an exercise machine. A higher-repetition maximum test (i.e., a 2–6 RM) may also be used to assess strength and estimate 1RM strength.[9]
Another option is an isometric strength test, which involves producing a maximal force against an immovable resistance.[11] Unlike dynamic resistance exercise, the muscle length does not change during an isometric muscle action. Strong correlations have been reported between maximum dynamic and isometric strength.[10]
What type of exercise is best for producing muscle strength?
In accordance with the principle of specificity — which states that training adaptations are specific to the demands imposed on the body — heavy loads (≥ 80% of 1RM) are superior to lighter loads for increasing 1RM strength.[12][13] Training to muscular failure (i.e., the point at which another concentric repetition cannot be completed with proper form) is not necessary to increase muscle strength.[14] In fact, ending each set a few reps shy of failure appears to be superior to training to failure for maximizing gains in 1RM strength.[15][16] Also, rest intervals between sets should be at least 3 minutes.[17][18]
Have any supplements been studied for muscle strength?
Supplements marketed to enhance muscle strength typically claim to do so through one of the following mechanisms or a combination of them: increasing muscle contractile efficiency (e.g., by improving calcium handling in the sarcoplasmic reticulum), delaying muscular fatigue, increasing the availability of fuel sources (e.g., carbohydrate), and/or stimulating muscle protein synthesis.[19]
The most effective supplements for increasing muscle strength appear to be creatine,[20] protein,[21] and caffeine.[22] Other supplements that have been studied for muscle strength include nitrate, citrulline malate, HMB, alpha-GPC, taurine, ashwagandha, and omega-3 fatty acids.
How can diet affect muscle strength?
Nutrition plays an important role in increasing muscle strength through fueling exercise and promoting recovery and exercise-induced adaptations. These processes are mainly influenced by protein and carbohydrate intake. Evidence suggests that a total daily protein intake of about 1.6 grams per kilogram of body weight is ideal for supporting increases in strength.[23][21]
Muscle glycogen is a primary fuel source during resistance exercise,[24] and glycogen depletion is associated with muscle fatigue and impaired muscle contraction efficiency,[25] so consuming at least 3–5 grams of carbohydrate per kilogram of body weight per day is recommended to maximize strength gains.[23]
With that said, many studies have not found differences in strength gains between higher- and lower-carbohydrate diets,[26] particularly when the resistance exercise routine includes low volumes (< 10 sets per workout), high loads (≥ 80% of 1-repetition maximum), and long rest periods (≥ 3 minutes of rest between sets). However, there is a lack of evidence demonstrating benefits of lower-carbohydrate diets for muscle strength.
Which other factors affect muscle strength?
Differences in muscle strength between individuals seem to be mostly explained by differences in muscle mass,[27][28][29][30][31] which is supported by the mechanistic rationale that a larger muscle has greater force-generating capacity.[32] Other contributors to muscle strength include neural factors,[8] such as the threshold at which motor units are recruited and the motor unit discharge rate, and genetics.[33] Additionally, simply practicing the test used to examine strength (e.g., a back squat 1-repetition maximum) can promote increases in strength.[34][35]
Examine Database: Muscle Strength
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In this meta-analysis of randomized controlled trials, supplemental vitamin E did not improve recovery from exercise-induced muscle damage, soreness, and strength and had no effects on blood markers of inflammation and oxidative stress after an acute physical exercise session.
Frequently asked questions
Muscle strength refers to the ability to produce force against an external resistance.[8] It is often divided into specific types of strength, such as lower body strength or upper body strength.
Strength is commonly assessed using dynamic resistance exercise,[9] which includes concentric (muscle shortening) and eccentric (muscle lengthening) muscle actions. The most popular method is a 1-repetition maximum (1RM) test,[10] which involves lifting as much weight as possible for one repetition using either free weights or an exercise machine. A higher-repetition maximum test (i.e., a 2–6 RM) may also be used to assess strength and estimate 1RM strength.[9]
Another option is an isometric strength test, which involves producing a maximal force against an immovable resistance.[11] Unlike dynamic resistance exercise, the muscle length does not change during an isometric muscle action. Strong correlations have been reported between maximum dynamic and isometric strength.[10]
In accordance with the principle of specificity — which states that training adaptations are specific to the demands imposed on the body — heavy loads (≥ 80% of 1RM) are superior to lighter loads for increasing 1RM strength.[12][13] Training to muscular failure (i.e., the point at which another concentric repetition cannot be completed with proper form) is not necessary to increase muscle strength.[14] In fact, ending each set a few reps shy of failure appears to be superior to training to failure for maximizing gains in 1RM strength.[15][16] Also, rest intervals between sets should be at least 3 minutes.[17][18]
Low to moderate volumes are sufficient to promote increases in strength. A 2017 meta-analysis reported that performing ≤ 5 sets per week substantially increased strength, with slightly greater gains with higher volumes.[36] There was insufficient data to determine whether 10-12 sets per week produced greater strength gains than 5–9 sets per week.
Other evidence indicates that performing 3–6 sets of 1–5 repetitions per week using loads ≥ 80% of 1-repetition maximum (1RM) and ending sets approximately 1–4 repetitions shy of muscular failure promotes meaningful increases in 1RM strength in resistance-trained individuals.[37]
Higher volumes don’t appear to provide benefits beyond that of low to moderate volumes, and might even be detrimental for strength gains by causing greater amounts of fatigue and delaying recovery from exercise. A study in resistance-trained men found that performing flat barbell bench press and barbell military press three times per week for a total of 6 sets per week was as effective as performing 18 or 30 sets per week for increasing bench press 1RM, and performing barbell back squat, leg press, and leg extension three times per week for a total of 9 sets per week was as effective as 27 and 45 sets per week for increasing squat 1RM.[38] Similarly, a 1997 study in resistance-trained men found that performing 4 sets of upper-body presses once per week was as effective as performing 8 or 16 sets per week for increasing bench press 1RM, and performing 3 sets of quadriceps exercises per week was as effective as performing 6 or 12 sets per week for increasing squat 1RM.[39]
A potential limitation of these studies is that the participants were instructed to perform each set to muscular failure. However, a meta-analysis currently in the preprint stage reported that lower-volume, lower-effort (i.e., sets were stopped further from muscular failure) resistance exercise programs produced similar (potentially greater) gains in lower-body strength than higher-volume, higher-effort programs.[16]
An increasingly common way to prescribe resistance exercise is to use a velocity loss threshold (VLT). The performance of resistance exercise according to a VLT means that once a certain percentage of velocity loss from the first repetition of a set is obtained, the set is terminated. For example, a VLT of 25% would mean that the individual stops performing repetitions once they complete a rep that has a velocity 25% slower than the first repetition. Consequently, a lower VLT typically means (depending on the load used and the individual’s first rep velocity) sets are completed further away from muscular failure than sets with a higher VLT. Evidence suggests that VLTs ≤ 25% are superior to greater VLTs for increasing strength.[15][16] Why might that be the case?
One hypothesis for the superior effects of lower VLTs is mitigating muscle damage.[15] Training to muscular failure produces greater muscle damage and neuromuscular fatigue than ending sets a few reps shy of muscular failure.[40][41][42] Muscle damage negatively affects the recruitment of high-threshold motor units and the ability of muscles to produce force,[40] as well as motor skill learning.[43] It also delays recovery from exercise, which can lead to a reduction in training frequency and less exposure to the exercise(s) on which the individual is interested in increasing strength. Therefore, training to muscular failure can compromise increases in muscle strength, particularly for complex movement patterns, by impairing training quality.[15] By training with a lower VLT, an individual can lift heavy loads (≥ 80% of 1-repetition maximum; the most important factor for increasing strength) and practice the exercise of interest more often.
Another hypothesis is that training with lower VLTs preserves muscle phenotypic characteristics that are favorable for maximum force-generating capacity.[15] One 8-week study found that training with a 40% VLT produced a reduction in the proportion of type IIX muscle fibers (the fastest and most powerful muscle fiber type) compared to a 20% VLT.[44] Because type II muscle fibers possess a higher force-generating capacity and generate force more rapidly than type I muscle fibers, training regimens that retain or increase the proportion of type II muscle fibers are theoretically superior for strength adaptations.
Periodization refers to the manipulation of training variables over time or the long-term planning of training. Linear periodization (LP) is characterized by increasing intensity and decreasing volume (i.e., lifting heavier loads for fewer reps) over time. Undulating periodization (UP) is characterized by more frequent variations in volume and intensity than LP. Weekly UP (WUP) involves fluctuations in volume and intensity from week to week, whereas daily UP (DUP) involves fluctuations in volume and intensity from workout to workout.
For example, consider a training program that involves performing resistance exercise twice per week for 8 weeks. Sample LP, WUP, DUP, and nonperiodized programs might look like this:
| Program type | Sample exercises |
|---|---|
| LP | 4 sets of squats using 70% of 1-repetition maximum (1RM) each workout for 4 weeks, followed by performing 3 sets of squats using 80% of 1RM each workout for 4 weeks |
| WUP | 4 sets of squats using 70% of 1RM each workout in week 1, followed by performing 3 sets of squats using 80% of 1RM each workout in week 2; alternate between weeks 1 and 2 for the rest of the 8 weeks |
| DUP | 4 sets of squats using 70% of 1RM in the first workout of the week and 3 sets of squats using 80% of 1RM in the second workout of the same week, for all 8 weeks |
| Nonperiodized | 3 sets of squats using 75% of 1RM every single workout for 8 weeks |
A 2022 meta-analysis reported that periodized training programs were superior to nonperiodized training programs for increasing 1RM strength, with a trivial-to-small effect size reported.[45] Concerning the type of periodization, UP (which included studies that utilized either DUP or WUP) was superior to LP for increasing 1RM strength, with a trivial-to-small effect size reported. Additionally, UP was only superior to LP in studies featuring trained participants.
Supplements marketed to enhance muscle strength typically claim to do so through one of the following mechanisms or a combination of them: increasing muscle contractile efficiency (e.g., by improving calcium handling in the sarcoplasmic reticulum), delaying muscular fatigue, increasing the availability of fuel sources (e.g., carbohydrate), and/or stimulating muscle protein synthesis.[19]
The most effective supplements for increasing muscle strength appear to be creatine,[20] protein,[21] and caffeine.[22] Other supplements that have been studied for muscle strength include nitrate, citrulline malate, HMB, alpha-GPC, taurine, ashwagandha, and omega-3 fatty acids.
Nutrition plays an important role in increasing muscle strength through fueling exercise and promoting recovery and exercise-induced adaptations. These processes are mainly influenced by protein and carbohydrate intake. Evidence suggests that a total daily protein intake of about 1.6 grams per kilogram of body weight is ideal for supporting increases in strength.[23][21]
Muscle glycogen is a primary fuel source during resistance exercise,[24] and glycogen depletion is associated with muscle fatigue and impaired muscle contraction efficiency,[25] so consuming at least 3–5 grams of carbohydrate per kilogram of body weight per day is recommended to maximize strength gains.[23]
With that said, many studies have not found differences in strength gains between higher- and lower-carbohydrate diets,[26] particularly when the resistance exercise routine includes low volumes (< 10 sets per workout), high loads (≥ 80% of 1-repetition maximum), and long rest periods (≥ 3 minutes of rest between sets). However, there is a lack of evidence demonstrating benefits of lower-carbohydrate diets for muscle strength.
A hypocaloric diet impairs muscle protein synthesis[46][47][48] and increases muscle protein breakdown.[49] It can also unfavorably alter the anabolic hormone response to resistance exercise.[50] Furthermore, prolonged consumption of a hypocaloric diet can facilitate endocrine system dysfunction, resulting in a suppression of reproductive and metabolic hormones and unfavorable alterations in markers of bone metabolism.[51] For these reasons, a hypocaloric diet would be expected to negatively affect muscle strength.
However, a 2021 meta-analysis that compared the effects of performing resistance training in an energy deficit or without an energy deficit reported that, while an energy deficit impaired lean mass gains, it did not impair strength gains;[52] interventions that prescribed resistance training in an energy deficit and without an energy deficit both resulted in a large increase in muscle strength. Furthermore, the average energy deficit in the included studies was 567 kcal per day.
A caveat to these findings is that the studies included in this meta-analysis were between 3 and 28 weeks long, with an average intervention duration of about 16 weeks. While the results suggest that increases in muscle strength can occur in an energy deficit in the short term, spending too much time in an energy deficit will undoubtedly compromise long-term strength gains. This stems from the fact that, as outlined in “Which other factors affect muscle strength?,” differences in muscle mass largely explain differences in muscle strength. Because an energy surplus enhances muscle gain (while an energy deficit impairs gains in muscle mass and can cause muscle loss), and a larger muscle has greater force-generating capacity, individuals interested in maximizing strength gains should spend a notable amount of time performing resistance training in an energy surplus.
Differences in muscle strength between individuals seem to be mostly explained by differences in muscle mass,[27][28][29][30][31] which is supported by the mechanistic rationale that a larger muscle has greater force-generating capacity.[32] Other contributors to muscle strength include neural factors,[8] such as the threshold at which motor units are recruited and the motor unit discharge rate, and genetics.[33] Additionally, simply practicing the test used to examine strength (e.g., a back squat 1-repetition maximum) can promote increases in strength.[34][35]
References
Examine Database References
- Oxidative Stress Biomarkers - Bloomer RJ, Farney TM, Trepanowski JF, McCarthy CG, Canale RE, Schilling BKComparison of pre-workout nitric oxide stimulating dietary supplements on skeletal muscle oxygen saturation, blood nitrate/nitrite, lipid peroxidation, and upper body exercise performance in resistance trained menJ Int Soc Sports Nutr.(2010 May 6)