Within-Session Responses to High Intensity Interval Training in Spinal Cord Injury

Abstract

High intensity interval training (HIIT) has shown to be a robust alternative to traditional aerobic training (Gillen et al. 2014, 2016; Astorino et al. 2011). In most individuals, incorporation of HIIT elicits increases in maximum oxygen uptake and overall health status, yet its feasibility in persons with spinal cord injury (SCI) is unknown. PURPOSE: The aim of this study was to compare acute changes in cardiorespiratory and metabolic variables during different HIIT regimens versus moderate intensity continuous exercise training (MICT). METHODS: Nine habitually active men and women (injury duration = 6.8 ± 6.2 yr) with SCI initially underwent determination of peak oxygen uptake (VO2peak) on an arm ergometer. During subsequent sessions, they completed MICT, HIIT, or sprint interval training (SIT). MICT consisted of 25 min of arm cycling at 45 %Wpeak. HIIT consisted of eight 60 s bouts at 70 %Wpeak separated by 90 s of active recovery at 10 %Wpeak, while SIT required eight 30 s bouts at 105 %Wpeak separated by 120 s of active recovery at 10 %Wpeak. Gas exchange data, heart rate (HR), and blood lactate concentration were measured. Each session was broken up into 16 phases (eight exercise and eight recovery data points for HIIT/SIT) for which mean oxygen uptake and HR were determined. RESULTS: Peak VO2 was higher (p = 0.03) in response to HIIT (1.13 ± 0.44 L/min at bout 8) and SIT (1.02 ± 0.37 L/min at bout 8) compared to MICT (0.90 ± 0.29 L/min), but mean VO2 was similar (p > 0.05) between MICT (0.86 ± 0.17 L/min), HIIT (0.89 ± 0.20 L/min), and SIT (0.82 ± 0.19 L/min). Peak HR was higher (p < 0.05) with HIIT (90 %VO2peak and 99 % HRpeak) and SIT (80 %VO2peak and 96 %HRpeak) versus MICT. There was no difference in mean HR across bouts (p = 0.16) which was equal to 130.7 ± 19.3, 129.3 ± 18.6, and 126.9 ± 14.9 b/min for HIIT, SIT, and MICT, equivalent to 79 - 82 %HRpeak. CONCLUSION: Despite a higher intensity, all participants preferred HIIT or SIT versus MICT. Compared to MICT, submaximal or supramaximal interval training elicits higher peak oxygen uptake and heart rate. The long-term efficacy and feasibility of HIIT in this population should be explored, considering that exercise intensity seems to be the most important variable manipulated in exercise programming to optimize maximal oxygen uptake. This study was partially funded by a University GPSM grant.