Heart rate and maximum isokinetic tests and muscle fatigue
Authors: Duvallet Alain , Duvallet Emilie , Lhuissier François , Beaudry Michèle 
Published: May 2023

Exercises in isokinetics are increasingly used for training and rehabilitation during various pathologies. The muscular response and adaptation allow the evaluation and relevance of rehabilitation program. Isokinetic fatigue tests measure an effort against an adapted resistance during a controlled movement. They involve a joint and the muscles allowing the movement. The fatigue test is carried by maximal work involving cardiac, vascular and metabolic response of the entire body.The variations of heart rate are the result of adapted and combined action of two systems with predominance of the sympathetic system during intense exercise. May an intense localized striated muscle effort be enough to elicit a significant cardiac response?The aim is to study the cardiac response during such an exercise and in particular the cardiac load that may have a role in the cardiovascular risks of this practice.11 healthy subjects mean age of 26.7 ± 6.2 years participated in muscular work carried out on isokinetic dynamometer during movements to 180°/sec for flexion-extension of the leg on the thigh. (6, 15 or 30 movements, in isolated tests separated by 24 hours, or in combined tests separated by 15 minutes). Peak of strength, work, and fatigability were collected.Cardiac electrical activity was monitored with electrocardiography and recorded on a heart rate monitor for heart rate analysis at different times before, after exercise and during recovery.Data were expressed as mean ± SD, variance and analyzed by a student t-test or Welch test on means (significance p<5%).Maximum force peaks didn’t significantly differ between tests. The tests with 6 and 15 repetitions were too short to analyze the fatigue index. It could only be analyzed during the test with 30 repetitions (55.9% +/- 11.2 and 51.4% +/- 8.4 in flexion and 61.3% +/- 8.4 and 58.3% +/- 9.4 in extension). There was no significant difference between isolated and combined tests. Heart rate was a function of test duration, with an increase between 6, 15 and 30 repeats, both during isolated and combined tests. The difference was not significant.The maximal heart rate during isokinetic tests could only be analyzed while repeating the movement 30 times. The maximal heart rate was to 167.4 bpm +/- 17.7 and 169.7 bpm +/- 11.9 or to 86.5% +/- 7.5 and to 87.8% +/- 6.0 of the theoretical maximal rate. The difference was not significant.Power peaks didn’t depend on the number of repetitions or the type of protocol.The results demonstrated the importance of the heart rate imposed by these tests, which only brought into play a relative limited muscle mass. The endurance test as strenuous exercise may pose a cardiac risk.Isokinetic tests are increasingly used during functional exploration of muscular force. This study confirms that isokinetic tests must be performed under the supervision of a clinician, who should evaluate the value and feasibility of a fatigue test. ADMS, private foundation grants This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.