When I started working out over three decades ago I believed, as many still do, that there is a load and repetition continuum that determines the adaptations to strength training; that heavy loads and short sets are better for strength, moderate loads and set durations are better for hypertrophy, and lighter loads and longer sets are better for local muscular endurance. Later, I learned from Ken Hutchins and Arthur Jones that this is not the case, that these are related and tended to improve together, although it might not seem that way since the exact relationship between them varies between individuals.
About five years ago, a study came out that confirmed that as long as you train intensely enough—perform exercises to momentary muscle failure—the load and repetition range or time under load (TUL) doesn’t make much difference for improving muscular strength and size:
“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.”
Morton, R. W., Oikawa, S. Y., Wavell, C. G., Mazara, N., McGlory, C., Quadrilatero, J., Baechler, B. L., Baker, S. K., & 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, 121(1), 129–138. https://doi.org/10.1152/japplphysiol.00154.2016
Over the past few years, several other studies have confirmed this, with one caveat: although a broad range of loads and repetitions or set durations can be equally effective for increasing both muscular strength and size, if you want to be able to lift as much weight as possible in a specific exercise you must practice performing that exercise with very heavy loads. This has, of course, lead to some confusion since one-rep max attempts are often used to test strength (isolated, static testing should be performed instead to minimize the influence of skill).
Schoenfeld, B. J., Grgic, J., Van Every, D. W., & Plotkin, D. L. (2021). Loading recommendations for muscle strength, hypertrophy, and local endurance: A re-examination of the repetition continuum. Sports, 9(2), 32. https://doi.org/10.3390/sports9020032
“In this meta-analysis, there were no significant differences between low-load and high-load resistance training on hypertrophy of type I or type II muscle fibers.”
Grgic, J. (2020). The effects of low-load vs. High-load resistance training on muscle fiber hypertrophy: A meta-analysis. Journal of Human Kinetics, 74, 51–58. https://doi.org/10.2478/hukin-2020-0013
While all of this seems to suggest there is no best load or rep range/TUL for strength or hypertrophy (as opposed to optimizing performance of competitive lifts), it is important to consider these are not the only things we desire from exercise. We also want to stimulate improvements in cardiovascular and metabolic efficiency and minimize the risk of acute and overuse injuries. Both of these goals are better achieved with more moderate loads and longer TUL (but not necessarily higher reps, since TUL can also be increased by performing reps more slowly).
Longer, more fatiguing sets have a greater effect on metabolic and cardiovascular efficiency. Using lower loads result in less compression and distraction of joints and makes it easier to maintain correct positioning and the correct path and range of motion. So, although a broad range of loads and repetitions or set durations can be equally effective for stimulating increases in both muscular strength and size, for overall strength and conditioning and long term joint health it is best to use more moderate loads and longer TUL.
In addition to saving time by eliminating the need for separate steady state or sprint interval training for cardiovascular and metabolic conditioning, when performed properly with slow movement (or even statics) and minimal acceleration during the turnarounds, strength training is easier on the joints and spine and has a lower risk of musculoskeletal injuries. Due to greater venous return resulting in higher stroke volume and cardiac perfusion (as long as Val Salva’s maneuver is avoided) high intensity strength training is also safer for the heart than traditional endurance activities.
Since you don’t need to perform exercises with a very heavy weight to maximize muscular strength and size gains you also don’t need long rests between exercises. You can save even more time and create even greater cardiovascular demand by limiting your rest between exercises. I recommend resting at least long enough between exercises so you do not become light headed, dizzy, or nauseated, but not so long your heart rate and breathing return to normal. As your conditioning improves you will find you need less rest between exercises (and you can track this by recording the start and end time and duration of your workouts).
As for load and TUL, while some people may find they prefer or do better with a little shorter or longer times, a good starting point for most is to use a load that allows you to achieve momentary muscle failure between 60 and 90 seconds using very strict form. This allows for around 6 to 10 repetitions at a moderately slow cadence (completing the positive and negative phases in around 4 to 5 seconds and with smooth turnarounds), or 3 to 5 SuperSlow repetitions (completing the positive and negative phases in around 8 to 12 seconds).
Want to learn More?
Join the HIT List community today and watch the following videos:
The Effect of Short Rest Between Exercises on Load and Muscle Strength and Hypertrophy
Load, Intensity, Inroad, and Safety
When Training to Momentary Muscle Failure Does Load or Time Under Load Matter?
Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance
Cardiovascular and Metabolic Adaptations to High Intensity Training
Rest Between Sets, Tension, Metabolic Stress, and Muscle Hypertrophy
Why You Don’t Need “Cardio” for Cardiovascular Conditioning or Fat Loss
Comments on this entry are closed.
One of my worst grown-phases was early to mid-90’s, adhering to Dinosaur Training. The premise sounded good, but chasing ever increasing poundage’s didn’t equate to size gains. Once I ditched that mindset, and became more muscle-focused, my gains resumed. And while I progress every single workout (in reps and/or weight), I see it as a means to an end, and not an end in itself. Ever increasing poundage’s is the nature of the beast. As Mike wisely said; “what are you supposed to do…grow weaker”?
For decades I was a low-rep guy (5-6 reps). But with age, and reduction of synovial fluid (explained to me by a senior nurse), upping my reps has been kinder on my joints and progress. Years ago I considered 8-10 reps “high”, nowadays I’m not afraid to venture into the 12-15 reps realm (if it’s failure). I’ve become less rigid and open minded. My joints have thanked me every step of the way. One of my major concerns is to regret what I’m doing now, crippling me later in life (as many pros have/do).
It is safer for the joints to increase TUL by performing slower repetitions than to do more. I only perform 2-4 reps per exercise, but they’re slow enough that this takes around 45-90 seconds.
Drew,
I read the underlying studies and understand that strength and hypertrophy gains can be made across a wide range of load and repetition schemes. However isn’t there some MINIMAL TUL required to stimulate growth? At the extreme low range I could do a one rep personal maximum. It seems to me that, while this is certainly my maximum load, a single rep would provide insufficient TUL (even at a slow rep cadence).
There are a lot of other considerations for TUL beyond just strength and hypertrophy. I discuss these in several videos in the HIT List.