A new study published in the Journal of Physiology shows that neither load nor brief post-workout increases in anabolic hormones determines muscular strength or size gains as long as exercises are performed to momentary muscular failure. While some individuals may respond a little better to higher reps or higher loads, on average a broad range of reps and loads can be effective as long as you train intensely enough. As the authors state in the abstract, “…in resistance-trained individuals load, when exercises are performed to volitional failure, does not dictate hypertrophy or, for the most part, strength gains.”
Morton, R. W., Oikawa, S. Y., Wavell, C. G., Mazara, N., Mcglory, C., Quadrilatero, J., . . . Phillips, S. M. (2016). Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men. Journal of Applied Physiology J Appl Physiol. doi:10.1152/japplphysiol.00154.2016
Forty-nine resistance-trained men (mean ± SEM, 23 ± 1 y) performed 12 wk of whole-body RT. Subjects were randomly allocated into a higher-repetition (HR) group who lifted loads of ~30-50% of their maximal strength (1RM) for 20-25 repetitions/set (n=24) or a lower-repetition (LR) group (~75-90% 1RM, 8-12 repetitions/set, n=25), with all sets being performed to volitional failure. Skeletal muscle biopsies, strength testing, DXA scans, and acute changes in systemic hormone concentrations were examined pre- and post-training. In response to RT, 1RM strength increased for all exercises in both groups (p < 0.01), with only the change in bench press being significantly different between groups (HR: 9 ± 1 vs. LR: 14 ±1 kg, p = 0.012). Fat- and bone-free (lean) body mass, type I and type II muscle fibre cross sectional area increased following training (p < 0.01) with no significant differences between groups. No significant correlations between the acute post-exercise rise in any purported anabolic hormone and the change in strength or hypertrophy were found. In congruence with our previous work, acute post-exercise systemic hormonal rises are not related to or in any way indicative of RT-mediated gains in muscle mass or strength. Our data show that in resistance-trained individuals load, when exercises are performed to volitional failure, does not dictate hypertrophy or, for the most part, strength gains.
Unlike many other resistance training studies which use a relatively small number of untrained subjects and tend to only last six to eight weeks this one used forty-nine men with at least two years of previous resistance training experience and lasted twelve weeks, making the results more reliable and relevant to training beyond the beginner stage. The subjects were randomly divided into two groups; a higher rep group that used thirty to fifty percent of their one rep max to perform sets of twenty to twenty-five repetitions, and a lower rep group that used seventy-five to ninety percent of their one rep max for sets of eight to twelve repetitions. Each group performed four brief, full-body workouts per week, consisting of three sets to momentary muscular failure of each exercise:
- Leg Press super-setted with Seated Row
- Bench Press super-setted with Cable Hamstring Curls
- Front Planks
- Shoulder Press super-setted with Bicep Curls
- Triceps Extensions super-setted with Wide-Grip Pulldowns
- Leg Extensions
I would have preferred the subjects perform only one set to failure and combine the exercises into two longer full-body workouts instead of the four shorter ones. Since most other studies show no significant difference in muscular strength and size gains between single and multiple sets or when performing more than two or three full-body workouts per week, this would have been just as effective but more time efficient.
Over the twelve weeks both groups increased muscular strength on all exercises, with no significant difference except the lower rep group improved slightly more in the bench press. Both groups had hypertrophy in both type I (slow twitch) and II (fast twitch) muscle fiber cross sectional area throughout the body with no significant difference. This confirms that a broad range of training loads and repetition ranges can be effective for improving muscular strength and size if exercises are performed to momentary muscular failure, and disproves the popular belief you must use lighter weights and higher reps to target your slow twitch muscle fibers and heavier weights and lower reps to target your fast twitch muscle fibers. The authors state, “The current data, along with previous work (28, 35), are direct proof that hypertrophy and strength gains are not a function of the load lifted and directly contradict the assertion that acute EMG recordings predict hypertrophic potential (21). Instead, we propose that exercising until volitional failure with adequate volume and load (between 30-90% 1RM) will sufficiently activate muscle motor units, which drives skeletal muscle hypertrophy.”
The study also disproves the popular belief that the acute hormonal effects of training with short rest periods or super-setting are beneficial for increasing muscular strength and size. They state, “post-exercise levels of circulating hormones did not change as a result of the RT intervention were unrelated to, and did not account for significant changes in, muscle mass or strength” and “In agreement with previous studies (50-52) it is clear that the post-exercise increases in systemic hormone concentrations are unrelated to changes in muscle hypertrophy or strength.” So rushing between exercises to increase growth hormone will not improve muscular strength or size gains as if often claimed, although it might still be beneficial for cardiovascular conditioning. I now question this as well, since research comparing sprint interval training with traditional endurance training shows it is not necessary to maintain a high metabolic demand and elevated heart rate continuously for this purpose.
Implications for training
While this shows a broad range of loads and repetitions can be effective there will be a point of diminishing returns below some level of load and above some time under load, and you should not expect to get the same results if you perform hour-long sets to failure using a very light weight. There is no mention in the study of the repetition cadence used so the exercises were most likely performed at typical speeds, meaning the high repetition sets probably did not exceed ninety seconds, and we can’t assume the same results using sets that are much longer than this. Also, while a broad range of repetitions can be effective on average, the optimal repetition range for some individuals may be lower or higher and may even vary between muscle groups and you should experiment and adjust your rep ranges or time under loads accordingly.
It should also be noted that while either low-load/high-rep sets or high-load/low-rep sets or anything in between can be effective for improving general muscular strength and size it is still necessary to perform specific high-load/low-rep sets to improve maximal strength in specific lifts (e.g. for increasing bench press or squat 1RM for competition) due to neural adaptations: “Though there is no apparent advantage of lifting with different loads on changes in muscle mass, there is undoubtedly a neuromuscular advantage to lifting heavier loads if the primary outcome is performing a 1RM test (28). Conversely, it appears that periodic practice of the chosen strength outcome (e.g. 1RM) is effective at eliminating the majority of any post-training difference.” For example, while low-load/high-rep sets to failure can improve your strength for powerlifting, you would need to increase the weight and reduce the reps on the competitive as you get closer to a contest.
If your goal is to improve your overall functional ability and physical appearance I recommend erring conservatively and using exercise loads that allow you to achieve momentary muscular failure within sixty to ninety seconds as a starting point (for example, six to ten repetitions at a 4/1/4 cadence, four to six repetitions at a negative-emphasized 4/1/10 cadence, or a 60 to 90 second static hold or timed static contraction). Using lower loads can make many exercises safer and using higher reps and a longer time under load can increase the metabolic and cardiovascular conditioning effect while being just as effective for improving muscular strength and hypertrophy.
This study also confirms that bodyweight high intensity training can be just as effective for increasing muscular strength and size as training with weights or machines as long as the method you use allows you to achieve momentary muscular failure within a reasonable time frame. This isn’t surprising, since I’ve been seeing these kinds of results in my bodyweight training clients for the past few years.
If your primary goal is building bigger, stronger muscles, you don’t need to rush between exercises to elevate growth hormone levels. While limiting rest between exercises may be more beneficial for cardiovascular and metabolic conditioning, and it will allow you to complete your workouts faster, doing so does not appear to have any effect on muscular strength and size increases. That being said, resting longer between exercises to increase the loads you are capable of using doesn’t appear to be necessary either. As a general guideline I recommend something in between; rest just long enough between exercises so cumulative systemic fatigue doesn’t interfere with your ability to perform subsequent exercises with a high intensity of effort and to achieve momentary muscular failure due to local muscular fatigue.