Abstract
BackgroundChronic spinal cord injury (SCI) increases morbidity and mortality associated with cardiometabolic diseases, secondary to increases in central adiposity, hyperlipidaemia and impaired glucose tolerance. While upper-body Moderate Intensity Continuous Training (MICT) improves cardiorespiratory fitness, its effects on cardiometabolic component risks in adults with SCI appear relatively modest. The aim of this study is to assess the acute effects of Continuous Resistance Training (CRT), High Intensity Interval Training (HIIT), MICT and rest (CON) on fasting and postprandial systemic biomarkers and substrate utilisation.MethodsEleven healthy, chronic SCI (> 1 year, ASIA A-C) men will be recruited. Following preliminary testing, each will complete four experimental conditions, where they will report to the laboratory following an ~ 10-h overnight fast. A venous blood sample will be drawn and expired gases collected to estimate resting metabolic rate (RMR). In order to ensure an isocaloric exercise challenge, each will complete CRT first, with the remaining three conditions presented in randomised order: (1) CRT, ~ 45 min of resistance manoeuvres (weight lifting) interspersed with low-resistance, high-speed arm-crank exercise; (2) CON, seated rest; (3) MICT, ~ 45 min constant arm-crank exercise at a resistance equivalent to 30–40% peak power output (PPO) and; (4) HIIT, ~ 35 min arm-crank exercise with the resistance alternating every 2 min between 10% PPO and 70% PPO. After each ~ 45-min condition, participants will ingest a 2510-kJ liquid test meal (35% fat, 50% carbohydrate, 15% protein). Venous blood and expired gas samples will be collected at the end of exercise and at regular intervals for 120 min post meal.DiscussionThis study should establish the acute effects of different forms of exercise on fasting and postprandial responses in chronic SCI male patients. Measures of glucose clearance, insulin sensitivity, lipid and inflammatory biomarker concentrations will be assessed and changes in whole-body substrate oxidation estimated from expired gases.Trial registrationClinicalTrials.gov, ID: NCT03545867. Retrospectively registered on 1 June 2018.
Highlights
Chronic spinal cord injury (SCI) increases morbidity and mortality associated with cardiometabolic diseases, secondary to increases in central adiposity, hyperlipidaemia and impaired glucose tolerance
The central hypotheses were that higher-intensity, intermittent upper-body exercise (i.e. High Intensity Interval Training (HIIT) and Continuous Resistance Training (CRT)) will enhance measures of fasting and postprandial insulin sensitivity and fasting triglyceride concentrations, compared to moderate-intensity exercise (MICT) or rest (CON)
Previous research suggests that higher-intensity exercise, resulting in greater skeletal muscle glycogen depletion within an individual session, is likely necessary to enhance biomarkers of cardiometabolic component risk, peripheral insulin sensitivity [43, 57, 58] and postprandial triglyceride concentrations
Summary
Chronic spinal cord injury (SCI) increases morbidity and mortality associated with cardiometabolic diseases, secondary to increases in central adiposity, hyperlipidaemia and impaired glucose tolerance. Chronic spinal cord injury (SCI) increases morbidity and mortality associated with cardiovascular [1] and metabolic diseases [2] These clinical outcomes are preceded by a higher prevalence of known risk factors including central adiposity [3], hyperlipidaemia [4] and impaired glucose tolerance [5]. While just 6 weeks of MICT can enhance fasting markers of hepatic insulin sensitivity in persons with paraplegia, the effects on postprandial markers of peripheral insulin sensitivity are negligible [10] Neither of these training studies were able to demonstrate a significant benefit of MICT on cardiometabolic components related to postprandial insulin sensitivity, hyperlipidaemia or systemic inflammation. Relatively little is known about the acute regulation of energy homeostasis at rest, during or post exercise in the SCI population
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