People often ask: “Should I do lots of reps with light weights, or few reps and heavy weights?”

The answer: neither, actually. There is a more precise measure of exercise performance, and it means you can stop counting reps.

[Just to clarify, a “rep” (repetition) is raising, then lowering, a weight—ending in the same position from which you began. A “set” is a series of reps, done back-to-back. A set of ten reps means moving a weight up and then down ten times.]

Like most people who train with weights, I used to focus on how many reps I did. I’d congratulate myself when I completed one or two reps more than in my previous workout. However, by keeping ever more detailed workout records, I discovered that in trying to do more reps, I often unconsciously moved faster and ended up spending equal or less total time doing the set… even when I had completed more reps.

While counting reps is a convenient way to judge exercise performance, the total duration of time the muscles are tensed and under load is more important. This is called “time under load,” or TUL.

Time Under Load (TUL) and Physiological Considerations…

Research suggests that the optimal TUL for best results is in a window of 1.5 to 3 minutes. This may be partially due to the rates at which different muscle fiber types are used and fatigue within a muscle.

Also relevant is the quality of muscular involvement during that TUL (constant or intermittent; concentric, eccentric, or static; degree of intensity).

• Ideally, muscular tension is continuous—with no stopping, pausing, or resting in any way.
• Ideally, exercise includes both concentric and eccentric effort—contracting (to lift a weight), and elongating (lowering a weight) while tensing against a resistance.
• Ideally, the intensity is such that the targeted muscle(s) becomes completely exhausted. Then, the TUL reveals the time it took to fatigue the muscle until it was physically unable move the weight, regardless of the mental will to do so.

Activities such as running engage muscles intermittently. This does not produce the same strength or metabolic benefits as continually engaging a muscle against constant resistance. Further, running, cycling, hiking, etc. have no eccentric component—which has time and again shown to be the most beneficial component of exercise. This is why we work with weights: they allow precision in exercising muscles the ways that generate maximum results.

When weight training, the average “set of 10” reps that people perform in gyms lasts 15-30 seconds—far below the ideal TUL. Also, much of that time is usually spent with the muscles not under constant tension due to pausing, letting momentum move the weight, and resting muscles by allowing the weight to basically fall while lowering it. Further, the acceleration involved in moving faster places greater forces on one’s joints, making an exercise potentially more dangerous.

A solution to all the above is to lift weights slowly and deliberately, making an effort to exhaust the targeted muscle(s), rather than being concerned with the number of repetitions completed.

While studies show that there are important differences between a 20-second, 90-second, and 300-second TUL, the exact number of reps performed during that time has not been shown to matter.

Note: it is sometimes appropriate to perform no reps at all (no movement: isometric) and engage a muscle against an immovable resistance for the desired TUL. This is often advisable for people who are starting off severely weak or recovering from an injury.

Weight Selection…

When we select weights for the clients we do personal training with here at Myogenics fitness in Los Angeles, we work to select the appropriate resistance for their strength level, whether they are 80 years old and out of shape and recovering from an injury, or a professional athlete. We select weights that one’s muscles can perform in a controlled manner for at least 90-180 seconds (using isometric exercises where appropriate).

The weight selection criterion is neither “heavy” nor “light.” The criterion is appropriateness for a given strength and ability level. As someone’s strength and skill increases, we adjust the resistance so that it continues to be appropriate.

Psychological Issues with Counting Reps…

From a psychological standpoint, counting reps becomes distracting and discouraging. The process of counting reps directs focus toward the external movement of weights, while taking focus away from what the muscles are doing, internally.

However, the real goal of exercise is not to move a weight up and down; it is to challenge a muscle to work it in a manner that results in the most positive physical change. The movement of a weight only matters in how well it aids the quality of muscular work.

The ideal point of focus is internal, on what is happening within the targeted muscle(s). The movement of weights is a means to this end.

Similarly, when driving a car, turning the steering wheel is the means to successfully navigating the streets. But if you were to focus exclusively on the steering wheel, your driving will not be as good or as safe (to put it mildly) as by focusing, instead, on the road ahead. In driving, observe the effect of your steering, rather than observing the steering itself. In exercising, observe the effect of the movements on your muscles, rather than the movement itself. Notice what is happening within your muscles if you slow or speed your movement.

When people think in terms of reps, and focus on the movement of the weights…

• they speed up to complete more reps—creating momentum that allows the targeted muscle some moments of rest
• they pause to rest the targeted muscle at the upper and/or lower turnarounds of a movement
• they start adjusting their body position and form, allowing other muscles to help out, so that the targeted muscles work less, and there is a larger tally of reps at the end of their set

As muscles fatigue, they steadily lose strength until they cannot physically complete a full rep; but it still may be possible to begin one. As someone nears this point, if the focus is on completing reps, it creates a sense of frustration, inadequacy, and failure at not being able to accomplish the goal of completing the rep. As a result, most people either give up and stop challenging their muscles (right where the exercise is most beneficial), or they sacrifice their technique and properly working the muscle to make the weight move.

When people focus on trying to exhaust their muscles, they experience satisfaction and success at accomplishing their goal as the exercise becomes tougher.

It can take vigilance to remind yourself that the exercise is not a battle with the weights to see how many reps you can perform, but, rather, a challenge in working with the weights to help you exhaust your muscles as much as you can—and in as little time (with as much efficiency) as possible.

How To Use This…

Here’s my current approach: instead of counting reps, get a stopwatch or clock (and ideally someone else to monitor it for you, so you can focus exclusively on exercising). Focus on challenging your muscles as much as possible by maintaining slow, smooth movement right up to the end of your set (when your muscles are physically incapable of moving the weight). Keep trying to engage the targeted muscles for a good 10 seconds after the weight will no longer move. Then look at the time you just spent. Any time spent without the muscle loaded–without proper form–does not count.

If your time exceeded the ideal of 1.5 to 3 minutes, then make the weights heavier for your next workout…so you’re not able to go as long. If your time fell short of the ideal TUL, lighten the weights for your next workout.Keep adjusting as necessary. As you begin to get it just right, you’ll feel a difference in the effectiveness of the exercise that must be experienced to be believed.

Of course, you’re always welcome to schedule a one-on-one workout with a personal trainer at our private facility here, in Los Angeles. One of our excellent LA personal trainers will be happy to guide you through everything discussed here (plus much more), give you feedback, keep you motivated, and take care of all the details of selecting and setting up the weights, so you can basically just show up.

Otherwise, go get a stopwatch, and start enjoying a more effective workout and a healthier, better looking body.

– Chad