Muscle Endurance: How to Increase It, According to Research

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Creapure® creatine monohydrate with certified purity exceeding 99.9%, in vegetable capsules manufactured in France. Three capsules daily provide 3 g of creatine monohydrate to replenish phosphocreatine reserves that fuel repeated sets.

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Researchers definelocal muscular endurance as the ability to resist fatigue in the face of submaximal resistance. It is distinct from maximum strength, measured on a single repetition with the heaviest possible load, the 1RM, and from cardiorespiratory endurance, which depends mainly on the heart and lungs. It is also local: enduring thighs do not make the arms enduring.

Two measures coexist.Absolute endurance counts repetitions with a fixed load, the same before and after training.Relative endurance counts them as a percentage of current maximum load, most often 40 to 60%. The distinction is far from trivial: depending on the test chosen, the conclusions of the same study can be reversed. In practice, studies use push-ups at a metronome rhythm, sit-ups, or the time held in a plank.

A Canadian cohort of 8,116 adults followed for 13 years points in the same direction for abdominal strength: the lowest-performing quarter in sit-ups had a mortality risk multiplied by 2.72 in men and 2.26 in women compared to the highest-performing quarter, after adjustment for age, smoking, weight, and aerobic fitness, while push-ups were not predictive. These are associations, not proof of cause and effect.

The long-taught explanation, an accumulation of lactic acid and hydrogen ions that would impair the functioning of contractile proteins, is probably of limited importance in mammals, according to a landmark review published in Physiological Reviews. The recognized mechanisms are multiple: impairment of action potential, insufficient calcium release in the muscle fiber, reactive oxygen species. Inorganic phosphate, released as phosphocreatine breaks down over contractions, appears to be a major cause of fatigue.

This fatigue can be delayed. The trained muscle neutralizes acidity better thanks to higher buffering capacity, produces more energy through aerobic pathways, and receives more blood thanks to new capillaries. These adaptations do not all respond to the same training: intervals act clearly on buffering capacity, as we will see below, while capillaries multiply with strength training, whether light or heavy.

The position of the American College of Sports Medicine is clear: for local muscular endurance, light to moderate loads, of 40 to 60% of maximum, sets of more than 15 repetitions and short rest periods, of less than 90 seconds. To make sense of it, trainers speak in RM, for repetition maximums: a load of 20 RM is one that can be lifted 20 times, not one more.

Studies confirm the benefits of long sets. In 32 untrained men, 8 weeks of sets of 20 to 28 RM most improved the number of repetitions at 60% of maximum, as well as aerobic power and time to exhaustion, while sets of 3 to 5 RM developed mainly strength. In 18 already trained men, sets of 25 to 35 repetitions increased repetitions at 50% of maximum by 16.6%, when sets of 8 to 12 left them nearly unchanged (−1.2%).

Heavy loads are not out of play either. In an 8-week trial on leg extension, sets to failure at 70% of maximum increased fixed-load repetitions from 22 to 26, the same gain as with sets at 15% of maximum, from 20 to 24. A 2021 review judges that the advantage of light loads remains equivocal: it appears mainly with fixed-load tests and for the lower body, and results diverge at equal percentage. In middle-aged adults and seniors, a meta-analysis finds large endurance gains, for the upper body (effect size of 1.10) as well as the lower body (1.18), regardless of intensity.

Volume matters. In a 6-month trial in 48 beginner men, 5 sets per exercise improved performance on 20 maximal repetitions on bench press more than 3 sets, which were themselves better than just one. On the leg press, 5 sets performed better than one alone.

Muscular failure is a tool, not an obligation. In a 16-week trial in 42 active men, sets taken to failure increased the maximum number of repetitions on bench press more than sets stopped before failure, for the same strength gain, +23% in both groups, and comparable progress on squat repetitions, +66% and +69%. It is also by going to failure that light loads match heavy loads in the trials cited above.

To progress, the American College of Sports Medicine proposes increasing the load by 2 to 10% as soon as you exceed the set target by one to two repetitions. Adding a set or shortening rest periods are two other levers.

Rest time directs adaptation. In 18 active women, 5 weeks of sets of 15 to 20 RM with 20 seconds of rest improved the ability to repeat sprints by 12.5%, versus 5.4% with 80 seconds; in return, maximum strength on the press increased by only 19.6%, versus 45.9%. Short rest periods improved repetition of intense efforts more, long rest periods improved strength more.

The circuit, which chains exercises with almost no pause, takes this logic further. In a trial conducted in 33 trained men, a heavy circuit with approximately 35 seconds of transition produced in 8 weeks the same gains in strength, power on the bench press, and shuttle run as traditional training with 3 minutes of rest, for shorter sessions, and only the circuit group lost fat mass.

Interval efforts directly train the mechanisms of local fatigue. In 16 women, 5 weeks of cycling with 2-minute intervals above the lactate threshold increased muscle buffering capacity by 25%, versus 2% with continuous training of the same volume, with comparable cardiorespiratory progress in both groups.

The reverse also holds true: strength training advances endurance athletes. In elite runners, a meta-analysis of 5 trials shows a significant effect of 8 to 12 weeks of strengthening, 2 to 3 times per week, on running economy. Our guides for preparing a marathon, a trail or a hyrox race detail how to incorporate it.

The method, called BFR for blood flow restriction, consists of training with a cuff inflated at the base of the limb. In 10 men, 4 weeks of leg extensions at 15% of maximum strength, 4 times per week, increased repetitions to failure by 63% on the leg equipped with the cuff, versus 36% on the free leg. In the 8-week trial mentioned above, a cuff tightened to 80% of occlusion pressure added 6 repetitions at fixed load, versus 4 without a cuff.

A meta-analysis of 77 studies shows that a night of 6 hours or less decreases physical performance by 7.56% on average, and strength endurance by 9.85%, an estimate still fragile due to the lack of numerous studies. All-nighters and early waking have the most impact, with approximately 0.4% of performance lost per hour of wakefulness before exercise, while late bedtime has little impact. Morning sessions are largely spared: after a short night, it's better to train early.

Mental fatigue also matters. According to a meta-analysis of 73 studies, a demanding intellectual task just before exercise reduces physical performance, especially in strength training: the effect reaches −0.57 on isometric efforts and −0.51 on dynamic efforts, versus −0.26 on aerobic effort.

Conversely, music helps: a meta-analysis of 139 studies attributes a favorable effect on physical performance (0.31), more pronounced with fast tempo, and a reduction in perceived effort (0.22).

Dehydration is costly. According to a meta-analysis of 28 publications, it reducesmuscular endurance by 8.3% and strength by 5.5%. Starting your session well hydrated is the first step, and the simplest.

Carbohydrates matter mainly in two situations. A meta-analysis of 21 trials shows that consuming them before or during the session increases training volume, with a significant effect after an 8-hour or longer fast and for sessions lasting more than 45 minutes; the two most favorable trials, conducted fasted, provided 1 to 1.5 g per kilogram of body weight 30 minutes to 2 hours before. Even a simple mouth rinse with a sugary solution adds an average of 1.24 repetitions, according to a meta-analysis of 13 trials, with no effect on maximum strength.

Proteins support adaptation rather than the session itself: in a meta-analysis of 49 trials, lean mass gains plateaued around 1.6 g per kilogram per day. A whey isolate helps achieve this intake, and our guide for building muscle details the calculation.

<<<20>>> Iron fer, finally, mainly concerns women with low reserves. In 20 non-anemic women whose ferritin was below 20 µg/L, 6 weeks of iron slowed strength loss during a thigh fatigue protocol, unlike placebo: at the end of the protocol, maximum strength was approximately 27% higher than before supplementation. A blood test allows you to check your ferritin; our guide on low ferritin details how to interpret it, and our bisglycinate iron can complement your intake.

Several supplements have measured effects on muscular endurance. These effects remain small to moderate: they don't replace training, they slightly increase its efficiency.

Caffeine. A meta-analysis of 34 studies, including 23 on endurance, found an effect of 0.28 on muscular endurance: approximately 18% (0.37) on tests conducted to exhaustion, no effect on fixed-duration tests. The position of the International Society of Sports Nutrition recommends 3 to 6 mg per kilogram, or 210 to 420 mg for 70 kg, most often 60 minutes before; very high doses, such as 9 mg per kilogram, multiply side effects without being necessary. With a half-life of 4 to 6 hours, it's best to avoid it later in the day, as detailed in our guide on caffeine before exercise.

Sodium bicarbonate. A meta-analysis of 13 studies measures an effect of 0.37 on muscular endurance, for both small and large muscle groups, with no effect on maximum strength. The position of the International Society of Sports Nutrition sets the minimum dose at 0.2 g per kilogram and the optimal dose at 0.3 g per kilogram, 60 to 180 minutes before exercise. Bloating, nausea, and abdominal pain are the most common side effects; their frequency, generally low, increases with dose: best to test first during training, ideally with a carbohydrate-rich meal.

Beta-alanine. It loads the muscle with carnosine, an acidity buffer: 4 to 6 g per day, in doses of 2 g maximum, increase carnosine by 40 to 60% in 4 weeks. Its overall effect remains modest (0.18), more pronounced, around 0.50, on capacity tests lasting 30 seconds to 10 minutes. In strength training, it mainly increased training volume and reduced perceived fatigue. Tingling is frequent and temporary, and nothing indicates it is harmful, as explained in our article on beta-alanine.

Citrulline malate. According to a meta-analysis of 8 trials, 6 to 8 g taken 40 to 60 minutes before the session add an average of 3 repetitions, or +6.4%, over several sets at approximately 70% of maximum (see our article on citrulline).

Beet juice. Rich in nitrates, it showed an effect of 0.43 on repetitions to failure in squats and bench press, in a meta-analysis of 6 small studies in trained men. The most favorable dose was approximately 6.4 mmol of nitrates, equivalent to a 70 mL shot, 2 to 2.5 hours before; the authors consider these results preliminary.

Our analysis of pre-workouts reviews these ingredients one by one.

Creatine increases muscle creatine and phosphocreatine reserves by 20 to 40%, the fuel for short and repeated efforts. After a loading phase, performance during intense or repeated exercise typically improves by 10 to 20%, according to the International Society of Sports Nutrition. Combined with training, it primarily allows you to accumulate more repetitions, session after session.

The dose: 3 to 5 g per day. The loading phase, approximately 20 g per day for 5 to 7 days, is optional: 3 g per day for 28 days achieves the same filling, around 20%, simply more slowly. Our Creapure® Creatine in capsules provides 3 g per day, our creatine powder 5 g, and our guide when to take creatine details the timing of intake.

Misconceptions hold up poorly against data. Weight gain in the first few days comes mainly from water retained by the body, 1 to 3 kg during a loading phase; no harmful effects on the kidneys have been observed in healthy individuals at recommended doses; the link with hair loss is based on a single study, never replicated. In 72 American football players training in the heat, those taking creatine even had fewer cramps. In case of kidney disease, medical advice is essential before starting. The benefits also apply to women, as shown in our article on creatine for women.

This program assembles the parameters that have proven effective in the cited studies. It is suitable for a healthy practitioner who already trains somewhat; a beginner can start with two sessions per week.

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