Non-responders to cardio exist don’t exist?

Do non-responders to endurance training exist?

Some people claim they cannot improve their fitness no matter how hard they train. These people are sometimes called hardgainers or non-responders.

In support, ~20% of subjects do not seem to improve cardiorespiratory function (e.g. oxygen uptake or maximal cycling workload) following intense endurance training.

This study investigated whether non-responders still exist when the training dose is increased. Therefore, subjects were divided into five groups: 1, 2, 3, 4, or 5 training sessions of 60 min exercise per week. Non-responders were defined as subjects that did not improve more than 4% (the measurement error, shown as the green line in the graph).

The number of non-responders decreased when increasing the number of exercise sessions per week from 1 to 3. There were no non-responders with 4 or 5 sessions per week.

After the first training period, the non-responders were put on a new training program, now with 2 extra training sessions a week. This time, all these non-responders improved after the training period, showing that they indeed needed more training sessions/volume per week to improve.

Study:
Montero D et al. Refuting the myth of non-response to exercise training: ‘non-responders’ do respond to higher dose of training. 2017

Go to the next infographic in the endurance series:
Breath restriction mask does not improve fitness?