Egwuonwu, would you please provide more details of your study? I believe the monitor could establish a baseline for the individual. Deviations in heart rate would then correspond to muscle fatigue. The issue is the complex response of the heart to hormonal changes, climate and other environmental changes, internal body changes - caffeine...etc, The fitness level of the individual and their sleep state will have an effect on their muscle fatigue for a given task. Will you be comparing changes within individuals or across individual (more complicated)?

Dear Dr. Egwuonwu,

I had realized with Ph. OBERT (specialized in heart) a study about muscle fatigue (EMGs investigation) and the slow component of VO2 max.

Our results :

Introduction – In one hand, during a fatiguing exercise the analysis of the myoelectric signal support the hypothesis of an increase of proportional number of active slow motor units. In the other hand, the slow component of oxygen consumption during a constant-rate-high- intensity exercise, seems to dependent on a progressive recruitment of fast-twitch fibers.

Methods and results – In front of this contradiction, the purpose of this study is to investigate the EMG activity of quadriceps femoris muscle during a 90% of PMA cycling exercise.

Two main results were observed: 1) Integrated EMG decreased all exercise long (from 0,99 to 0,86 v); 2) MPF and MDF decreased in the first part of the exercise (respectively from 82,5 to 81,25 Hz and from 108,75 to 107 Hz), followed by a progressive increase (respectively from 81,25 to 84,5 Hz and from 107 to 109,25 Hz).

Conclusion – Our results suggest a progression in the average frequency of the motor unit discharge towards the high frequencies, which coheres with the hypothesis of the progressive recruitment of fast-twitch fibers during the V~ O2 slow component.

Philippe Obert realized several publications with Dr Ch. Cleuziou (thesis) about relation between the VO2, the Heart rate and the activation of muscles.

Best regards

Philippe

On the most basic of levels, Borg's perceived exertion scale (6-20) measures overall fatigue during a task, and correlates quite well with HR.

I am grateful to Mathew, Philippe and Joan for your answers to my questions they are useful.