The question of how long muscle regeneration lasts is not easy to answer: Not only the intensity of the previous training is important, but also the ability of the muscle group itself to regenerate.
What is regeneration?
Muscle regeneration in our context means the restoration of a muscle that has been damaged in its finest structures by previous intensive stress (training). The regeneration repairs microscopically small injuries of the muscle. The training itself therefore represents a load that must be compensated by the process of regeneration.
Can muscle regeneration be measured?
As plausible as the description above may sound, you can’t really measure regeneration. Because one would actually have to check the injuries (micro-traumas) that are not visible to the naked eye and determine whether the healing process has already been completed.
And although there are now procedures for the body as a whole to determine the current degree of stress, the matter becomes complicated at the latest when you look at individual muscle parts: If one follows observations from the practice of experienced athletes and reports published in the relevant literature, one must assume that different muscles recover at different rates from the stress of the last training session.
How quickly do muscles regenerate?
The first and most important factor for the time a muscle needs for regeneration is, of course, the intensity of the previous training stimulus: the heavier the weights, the longer the time required. However, this is not the only factor:
Since the individual muscles recover at different times, the recovery times should also be considered in training plans. This is the only way to train each muscle in its optimal supercompensation.Trainer education document by Günter Robert Pölzer: Fitness in theory & practice, Volume 2 (National Fitness Academy Austria, 2019, page 160)
This means that not every muscle group regenerates at the same rate. For example, the lower back takes much longer to regenerate than the calves. These relationships have been known for about 30 years:
How much? How often? How hard? When it comes to recuperation, each muscle group has its own limits.Journal article by John Comereski: Formula for Recovery, in Muscle & Fitness 7/1992, page 104
How do I keep track of the processes of muscle regeneration?
In itself, it’s quite simple: you train an exercise and think about which muscles are involved in what kind in the movement: Which is the most trained muscle part and which other muscles are supportive? These “power ratios” are then weighted and linked to the intensity of the exercise execution. This results in the load of the individual muscle groups, which themselves have different “recovery speeds”. At the end of the day it remains to be seen when at the earliest which muscles should be subjected to a next training stimulus.
However, since this matter is surprisingly more complex than you might think at first glance, myTRS was developed: The web app is used to assign exercises from a catalog to the current training and to determine the intensity of the exercise. All further calculations are then taken over by myTRS and show in the colors of the traffic light system, when the individual muscle parts can be trained again (green), when they are absolutely to be spared (red) and on which days a training can take place, if it really must be (yellow).