Time vs. Sets

My manager asked me today, "are you still timing your exercises or using reps?". This of course got me thinking, why am I using time based exercises?

In general, I have been timing most of my TRX workouts in intervals of 30-45 seconds with 15 or so seconds of rest between them.

But still the question remains why? Convention would have you believe that reps and sets are the only way to go. This is a proven and time tested method of training and has it's merits and has been proved to promote hypertrophy. Rarely do you see someone bench pressing 80% of their body weight for 2 minutes and resting 15 seconds in between. Repetitions and sets give someone a clear idea of how much of an exercise they are going to perform, but not necessarily for how long.

So why time? Here are a few reasons:

1. Intensity. Exercises done in moderate to high intensity have shown to promote a metabolic boost. This will also build functional strength and endurance.
2. Time. Because most training sessions with my clients are 30 minutes in length. I have to find a way to know I'll be able to put my client through a quality workout, while still being able to get to my next client.
3. Volume. I've done both reps and time with the same client and have found strengths and weaknesses in both. Whether a person is able to perform more quality exercises in 30 seconds then if you were to give them a set number depends on the trainer. I've found with the TRX, an inexperienced client will perform less and lower quality repetitions if given a set number. As they will find a position that will allow them to easily perform them. As a trainer, you need to know how to identify these types of people and learn how to correct them.
4. Variability, the TRX is not an easy piece of equipment to quantify weight with. Where as with free weights and other equipment, the weight is usually put on the implement. With the TRX you are dealing with angles and torques that can change with a single step and body position.
   

Ultimately, it comes down to what your goal and/or preference is. Both sets and time have their merits and shortcomings. Which one is best for you comes down to what you want and what you want to accomplish.

I may post more on this later.