Modelling Exercise Training Load in Spinal Cord Injury: A case study

Abstract

It is unclear how best to prescribe or evaluate training in spinal cord injury (SCI) patients. The training impulse model (TRIMP) may be an effective means to quantify training load in SCI. PURPOSE: Determine whether heart rate (HR) TRIMP model can effective in quantifying training in SCI. STUDY METHODS: One male (34 yrs, 165 cm, 95.9 kg, ml·kg-1·min-1, 43.0 kg fat-free mass, VO2 Peak 1.28 L·min-1) T6 complete SCI patient, part of a larger exercise training study, underwent pre- and post-training evaluation to determine VO2 Peak during discontinuous arm crank exercise (ACE), while body composition was assessed using DXA. Training consisted of ∼57 min each day, 5 days per week for 16 wk of either ACE or functional electrical stimulation (FES) leg cycling. The subject completed a supervised program in which workload was increased progressively throughout the training period and HR was recorded using a Polar RS 800 HR monitor. HR TRIMP scores were based on four predetermined zones and calculated by multiplying the time in each zone by either 1 (Zone 1), 2 (Zone 2), or 3 (Zone 3), with the sum total representing that sessions TRIMP score. During session 1 (R1), 41 (R41) and 78 (R78), continuous VO2 data were collected using a Cosmed K4 b2 with VO2 and RER graphed for comparison. RESULTS: Improvements were seen in VO2 Peak (+9.4%), body mass (-10.4%) and fat-free mass (-8.6%). HR TRIMP showed an upward trend over the course of 16-wk, but compared to the mean session power (MSP) pattern, indicated a training plateau, or even localized overtraining. Mean training session HR and VO2 increased from R1, reflecting the increased session workload. RER data (R1=1.02, R41=0.93, R78=0.96) indicated typical training adaptations from R1 to R78, decreasing significantly (p=0.0003) between R1 and R78, despite the increase in workload. However, RER at R78 was significantly higher (p=0.004) than R4 indicating a possible overtraining effect. CONCLUSIONS: HR TRIMP scores appear to be a useful tool in monitoring training load, and perhaps periodizing training in SCI patients. RER responses suggest that persons with SCI show a reduced reliance on carbohydrates after training of FES, but may also suffer from localized overtraining of the stimulated muscle group. However, more data are needed to draw definitive conclusions.