[Short-term exercise-based cardiac rehabilitation induced changes in cardiorespiratory, mechanical and neuromuscular responses to progressive exercise testing]

Abstract

Previous studies showed that changes in peak of oxygen uptake value (VO_2peak) with training were poorly related to changes in Maximal Tolerated Power output (MTP) among patients with cardiovascular disease. This result could be due to a difference between cardiopulmonary adaptation to training and the skeletal muscle conditioning.

Objective: The aim of the study was to compare the responses to exercise training of electromyographic activities of vastus lateralis (rms-EMG) and respiratory parameters.

Methods: Nine cardiac patients (64.0±3.1y, 172.9±4.8cm, 83.4±16.3kg, BMI: 27.8±4.5) performed an incremental cycling exercise test to determine MTP, VO_2peak and peak values of heart rate, before and after an aerobic training. Ventilatory thresholds were respectively determined as the breakpoint in the curve of carbon dioxide output against oxygen uptake plot (VT₁) and the point at which the ratio of minute ventilation to carbon dioxide output starts to increase (VT₂). EMG_th1 and EMG_th2 were defined as the first and the second breakpoints in the rms-EMG - power output relationship.

Results: Short-term exercise training (23.7±8.8 days) induced a significant increase in VO_2peak (P=0.004), MTP (P=0.015), VT₁ (P=0.001) and VT₂ (P=0.001). Changes in VO_2peak only attained the survival criteria (3.5±2.9mLmin^-1kg^-1). No significant differences (P>0.05) existed between mean power values of VT₁ and EMG_th1 (60.5±4.1 vs. 59.2±9.6% of MTP, respectively), or between VT₂ and EMG_th2 (78.3±5.7 vs. 80.2±5.2% of MTP). After training, EMG_th1 occurred significantly before VT₁ (60.5±6.2 vs. 64.8±4.8% of MTP, P=0.049).

Conclusion: This might be taken into account for prescribing exercise rehabilitation according initial clinical limitations of patients.

Keywords: Adaptations neuromusculaires; Cardiorespiratory responses; Court séjour; Dissociation; Electromyography; Exercise-based cardiac rehabilitation; Réadaptation cardiovasculaire à l’effort; Réponses cardiovasculaires; Short-term training.