Determinants of nutritional requirements of spinal cord injured athletes : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Nutritional Science, Massey University

Abstract

Disability sport is attracting more participants and is becoming increasingly competitive. Athletes with spinal cord injury (SCI) resulting in quadriplegia face a number of physiological limitations such as reduction in lean body mass, increased fat mass and altered physiological responses to exercise, as a direct consequence of their injury. Long-term health consequences of spinal cord injury such as cardiovascular disease, type 2 diabetes and osteoporosis occur earlier than in the able-bodied population. The aims of this study was to investigate the nutritional status and some of the physiological characteristics likely to impact on the nutritional requirements of SCI athletes. Sixteen wheelchair rugby players currently playing for a regional team in the 1999 NZ National Wheelchair Rugby Tournament were recruited. Subjects completed a brief demographic questionnaire to provide information about their injury, and 7-day food diary for assessment of dietary intake during the competition season. Body composition and bone mineral density were assessed by dual-energy x-ray absorptiometry (DEXA) and an arm-cranking test was performed in a laboratory situation to assess heart rate response and oxygen uptake during exercise. Finally, monitoring of heart rate in a game situation was performed on three subjects. Body composition data showed that subjects had a body mass index (BMI) (26.4 g/cm2) similar to that of the general New Zealand population and to paraplegic subjects in New Zealand. However, lean body mass was low (60.1% of total body mass) and body fat was relatively high (34.9% of body mass) in comparison to both the general population and to other athletes. Mean whole body bone mineral density for the group was within the normal range however, five subjects were classified as having osteopenia and of those, two were classified as having osteoporosis. The mean energy intake was 8678 ± 2411 kcal per day, significantly below that of NZ males in the same age groups [1]. The contribution from carbohydrate, protein and fat to total energy intake was virtually identical to that of the general NZ population [1]. Many of the subjects did not meet the Recommended Dietary Intake (RDI) for a number of micronutrients. Heart rate (HR) response and oxygen uptake (VO2) was similar to that found in other studies [2]. Interestingly, the relationship between HR and VO2 showed a linear increase during the graded exercise test resulting in a coefficient of determination above 0.923 for all subjects. Heart rate profiles were recorded for three subjects in a game situation and energy expenditure was calculated from VO2 data from the laboratory exercise test. The three subjects had a calculated energy expenditure ranging from 3.7-7.2 kcal/minute of exercise. It was concluded that BMI may not be an accurate method to assess obesity in quadriplegic subjects and body composition assessment by DEXA provides a more accurate method for determining changes in body composition and bone mineral density over time. It was further concluded that many subjects had low energy intakes resulting in suboptimal intakes of macronutrients. Many subjects would benefit from dietary advice with a view to improve general health and exercise performance. Heart rate monitoring for the purpose of estimating energy expenditure should be investigated further in this population as should other factors likely to impact on both general health and exercise performance.