Why Shape  says paying attention to the clock instead of counting reps is your ticket to a stronger body.
Professionally, I am known as a bodyweight specialist who uses time as a measure of progression. I train this way with everyone from celebrities to those who are fighting obesity or in rehabilitation situations.
What I have found is that training by measuring the number of reps presents a few key issues: it doesn't encourage you to place muscles under stress for a maximum amount of time, which creates optimal results; it can lead to improper form since you feel you must eke out those 15 squat jumps; and — most imperatively in my opinion — you may fail to complete the prescribed reps, which could lead to feelings of negative self-worth.
I began to see significant improvements when I started training individuals to perform as many reps as personally possible within a designated time frame. This is why:
1. It Works for Any Fitness Level
The time that it takes to perform 12 pushups varies greatly from one individual to the next. Let's look at this example: One woman may press out a certain number in 10 seconds, while it may take another up to 30 or more seconds to do the same amount. That's a big difference in time, which may show variances in progress. Now take that same exercise and ask each woman to perform as many repetitions as possible (in a controlled manner) for 30 or 40 seconds. The first woman's repetition count would increase, forcing her muscles to work harder and challenging her at her own fitness level. The second woman, even though she is working at a slower pace, is keeping her body under constant stress as well, working her muscles just as hard for her abilities.
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2. It Puts the Focus on Form
It is important that your body learns proper form with any exercise. Whether you are a beginner or have been training for a long period of time, progress and safety happen from form. Take a newbie, for example. This individual will gain progress from implementing each exercise in a controlled manner. When asking a beginner to perform an exercise for a designated amount of repetitions, their concentration on performing all of those reps may supersede the importance of completing the exercise properly. Unfortunately this happens a lot, and it can lead to a great deal of bad habits that carry on negatively later as someone continues training. Keeping good form can happen easily with time-based exercises.
3. It Instills Confidence, Which Keeps You Motivated
Back in college, my track and field coach would have us stop performing an exercise if we reached a new personal record. This did not sit well with many of us, as we felt that one personal record would soon be followed by another. However, he stated that a personal record should be celebrated and applauded to instill confidence, and that if he let us go further with another attempt at the exercise, the failure to compete another rep might over shadow our PR. That year we went on to win the National Championships. His belief was that we never celebrated ourselves enough, and even our smallest victories should not get overshadowed.
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Training for time has a way of supporting my coach's philosophy. Think about this: How many times have you attempted to perform 12 reps and come up short by even just one? That one number off can result in a feeling of failure. Performing an exercise with 30 seconds to complete as many repetitions as you can not only sets a benchmark you can keep track of, but it can provide you with a sense of saying to yourself, "Hey, I can do this" or "I did 25...Wow!" That little piece of positivity is what can help to keep an individual consistent with their fitness program and gain a stronger sense of confidence within themselves.
I am not asking you to throw out your training protocols of repetitions. But I am asking you to consider incorporating working exercises for time. Mix it up, push your limits, and open your mind to what has worked as a positive training format for my clientele.