Cardiovascular responses to heat acclimatisation in athletes with spinal cord injury

Abstract

Objectives: To determine the effect of heat acclimatisation (HA) training on blood profile and resting cardiac function in elite athletes with spinal cord injury (SCI).

Design: Quasi-experimental.

Methods: Eleven athletes (10m, 1f) with SCI (C5-T3) completed a five-day isothermic HA protocol whereby gastrointestinal temperature (Tc) was elevated to and maintained at ∼38.5 degrees Celsius (°C) via intermittent exercise for sixty minutes each day. Blood samples were collected pre- and post-HA to determine changes in plasma volume (PV). Doppler ultrasound of the left-ventricular outflow tract and 2-d speckle tracking echocardiography were performed in a subset of athletes (n=5) to determine changes in indices of resting left-ventricular function and mechanics, respectively.

Results: Ten athletes were successfully able to raise and maintain Tc to 38.5°C. There was a non-significant increase in PV with HA training (ΔPV%: 3.0±5.4%, p=0.086). Following HA, resting HR decreased (63±4 pre-HA vs. 58±5 bpm post-HA, p=0.020), velocity time integral (21.4±2.7 vs. 23.7±3.0cm, p=0.045) and stroke volume increased (64.8±7.6 vs. 70.2±10.5mL, p=0.055).

Conclusions: Our findings suggest a short-term HA protocol in athletes with SCI is safe and may induce beneficial changes in indices of resting left-ventricular function - however results are highly individualized. Future studies on HA in athletes with SCI should focus on determining mechanisms of adaptation and performance outcomes.

Keywords: Cardiovascular system; Sympathetic nervous system; Thermoregulation; Wheelchair rugby.