A common question I hear from trainees, athletes and clients is “how do I know when it’s time to change my workout?” The traditional answer has been “when it stops working for you.” Recently I’ve come to realise just how useless this answer is because when all is said and done almost every workout will continue to give you some results if you do it consistently. The answer I prefer now is when the rate of adaption to the program slows to a critical rate.
To fully understand the implications of this you need to keep in mind that the body responds to physical work by adapting in two key areas (there are changes in many areas, but to know when it’s time to change a program we need to be concerned with only two areas) – the nervous system and muscular system. The nervous system is concerned with coordinating and transporting the commands that fire the muscle fibers. The muscular system is concerned with the changes within the muscle fibers themselves.
When we first start doing a program the specific demands of the workout are completely new to the body. For example, the rest pause training approach has a trainee perform a set in 3 segments with 15-20 seconds between each segment and 60-180 seconds of rest between sets. The goal is to complete the same predetermined number of reps during each segment. There are very few activities in the real world that mimic this training method so it is an effective way of boosting intensity, work capacity and time under tension.
During the first workout the body is very inefficient that coordinating the required muscle impulses needed to move the load as the workout requires. As a consequence the number of reps that is performed during each segment drops dramatically. When I first did this with behind the neck barbell press I was able to move 115 for 8 reps in the first segment, 5 reps in the second segment and 4 reps in the 3rd segment. With set two I did 105 7 times, 5 times, 4. Set 3 was 105 for 6, 4 and 4. My performance was basically the same for all other body parts, diminishing rep numbers after each pause and lower weight for each set. But it doesn’t take the nervous system long to adapt to the program and after about 3 weeks the behind the neck shoulder press numbers were 125 for 8, 6,5, 115 for 8,7,5 and 115 for 7,5,5.
Lets compare the first workout to the week 3 workout. My max weight I lifted went up from 115 to 125 for 8 reps. The lightest weight I lifted increase to 115 from 105 and the total number of reps I did for this exercise increased from 47 to 56. Overall the amount of work I did (assuming the time under tension remained constant for every rep) increased from 5105 units to 6630 units or about a 30% increase. NOTE: the units are an arbitrary measure that represents the weight multiplied by the number of reps.
So getting back to the CNS and muscle adaption, both contribute to the increase in work capacity and max weight lifted. How do we figure out what is responsible for the increase? My belief is that the improvement in the first segment of each set is the result primarily of muscle adaption while the increase in the second and third segments is the result of CNS adaption. My rational for this is that right before I was did rest pause I was doing push / pull sets and was able to lift 115 for 8 reps. The reason I say the CNS was primarily responsible for the increase in work ability in the 2nd and 3rd segments is that I had the muscle capacity to lift the weight (as indicated by the first segment), I simply didn’t have the capacity to get the muscle fibers to fire. After a few weeks, my CNS has developed the ability to recruit the muscle fibers needed to make the weight.
So how do we use this to figure out when it’s time to change a program? First off, the CNS will adapt much faster than the muscles do so we can use this as an indicator that we’re getting close. With rest pause, we would know that the CNS has adapted when we’re able to do the same number of reps with each set and segment for example, when set 1 and set 3 are made up of 8,6,5 reps each. CNS adaption is not complete, but it has reached what I would consider a critical level. Once you’re able to do that, you know that a program change is getting near.
Check back soon for Part 2 where I will outline how to identify the changes in the muscle system that indicate a program change is needed.