Cardiac effects of short term arm crank training in paraplegics: echocardiographic evidence

The cardiac responses of male paraplegics to upper-body endurance training have been studied by M-mode echocardiography and CO2-rebreathing determination of cardiac output. Data for nine exercised subjects are compared with 5 controls. After 16 weeks of arm ergometer exercise, heart rates of trained individuals were 9 bt X min-1 lower during isometric handgrip effort (30% of MVC for 3 min), with a substantial decrease of rate pressure product (20%; p less than 0.05). In contrast (possibly because of greater anticipation) the control subjects developed a larger rate-pressure product with repetition of the standard isometric effort. Despite a significant increase of VO2 peak (19% and 31% after 8 and 16 weeks, respectively; p less than 0.05), echocardiographic LV mass, dimensions and indices of LV performance were unchanged by training, either at rest or during the isometric handgrip. Stroke volumes were significantly increased by 12-16% after training, both in isometric and in rhythmic work; at the highest intensity of arm ergometry, there was also a suggestion of increased cardiac output. We conclude that a short period of arm training is insufficient to induce cardiac hypertrophy, an increase of stroke volume with a decreased rate-pressure product but no change in echocardiographic indices of LV performance implies an improved myocardial efficiency. Possible explanations are a greater strength of the trained arms, and some increase of pre-loading (due to an increase of venous tone and more effective operation of the muscle pump after training).