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 · min⁻¹ lower during isometric handgrip effort (30% of MVC for 3 min), with a substantial decrease of rate pressure product (20%;p<0.05). In contrast (possibly because of greater anticipation) the control subjects developed a larger rate-pressure product with repitition of the standard isometric effort. Despite a significant increase of \(\dot V_{{\text{O}}_{\text{2}} } \) peak (19% and 31% after 8 and 16 weeks, respectively;p<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 (1) a short period of arm training is insufficient to induce cardiac hypertrophy, (2) an increase of stroke volume with a decreased ratepressure product but no change in echocardioraphic indices of LV performance implies an improved myocardial efficiency. Possible explanations are (1) a greater strength of the trained arms, and (2) some increase of pre-loading (due to an increase of venous tone and more effective operation of the muscle pump after training).