Glycogen Utilization in Wheelchair-Dependent Athletes*

Abstract

Seven wheelchair-dependent endurance athletes (5 males, 2 females, mean age = 27 years, mean VO2 max = 2.01 1/min) consented to maximal and submaximal (SM) testing on a wheelchair ergometer for the purpose of determining aerobic capacity, plasma substrate concentration, and muscle glycogen utilization during prolonged exercise. Results from an initial graded maximal test were used to determine exercise intensity levels during a subsequent 1-h submaximal endurance ride on the wheelchair ergometer (60%-70% VO2 max). Muscle biopsy samples (N = 5) were taken from the M. deltoideus (anterior head) before and after the submaximal exercise. Hematocrit (Hct), hemoglobin (Hb), glycerol (G), glucose (Glu), and free fatty acids (FFA) measured from venous blood taken before, midway, and at completion of the SM test demonstrated changes in plasma volume and substrate level similar to those of other athletes observed while running on a treadmill or exercising on a cycle ergometer. Type I fibers were characteristically depleted of glycogen, as measured by PAS stain, as a result of the SM endurance ride. Pre-exercise glycogen values were similar among subjects (means = 92.46 mmol X kg-1 +/- SEM 1.8) while muscle glycogen utilization varied from 17.4 to 46.6 mmol X kg-1. These findings indicate that physiologic response patterns of the upper arm muscles of trained wheelchair athletes during acute endurance exercise correspond to those observed in the leg muscles of able-bodied endurance athletes.

Carbohydrate Considerations for Athletes with a Spinal Cord Injury

“…From these data, the author supplied individual data of an athlete with a T4 lesion level [26] similar to the athlete of Abel et al (2006) [68]. For the calculation of the available glycogen stores, data from Skrinar et al (1982) were used [70]. Fat-free mass in the arms was 9.039 kg [26], leading to 150.4 g of stored glycogen determined by the mean glycogen content of the deltoid muscle (e.g., 1.66 g/100 g wet muscle tissue) [70].…”

“…For the calculation of the available glycogen stores, data from Skrinar et al (1982) were used [70]. Fat-free mass in the arms was 9.039 kg [26], leading to 150.4 g of stored glycogen determined by the mean glycogen content of the deltoid muscle (e.g., 1.66 g/100 g wet muscle tissue) [70]. By offsetting the upper body muscles associated with handcycling, such as the rotator cuff, the trapezius and pectoralis muscle [69], a 10% higher fat-free mass and consequently glycogen storage capacity were presumed.…”

“…However, evidence suggests, that glycogen levels below 280–300 mmol per kg dry muscle mass possibly compromises Ca 2+ release rate from the sarcoplasmic reticulum, thereby diminishing muscle contractility [ 71 , 72 ]. The aforementioned critical threshold equals to 119.4 g glycogen in the calculated model, which would be reached after approximately 52 min without supplementation (assuming a linear glycogen utilization rate of 0.5 mmol/min/kg wet muscle tissue [ 70 ]). Hence, 29.3 g/h exogenous CHO supplementation would be required to stay above the critical threshold until the end of the competition.…”

Influence of Caffeine and Sodium Citrate Ingestion on 1,500-m Exercise Performance in Elite Wheelchair Athletes: A Pilot Study

“…In general, only a few studies explored the influence of other supplements on exercise performance in athletes with impairment. These researchers have focused on creatine supplementation (Perret et al, 2006) and carbohydrate ingestion (Skrinar et al, 1982;Spendiff & Campbell, 2005). Furthermore, data from studies conducted with able-bodied participants could possibly not be transferred one-to-one to spinal cord injured individuals, because of the physiological differences concerning active muscle mass (Maggioni et al, 2003;Nuhlicek et al, 1988), muscle fiber type distribution (Schantz et al, 1997) and gastrointestinal function (Krogh et al, 2000).…”

A new conceptual framework for the integrated neural control of locomotor and sympathetic function: implications for exercise after spinal cord injury

“…. During prolonged voluntary exercise (40-80 minutes at 60-65% VO 2peak ), those with lowlevel paraplegia also showed increasing serum free fatty acids and a decreasing respiratory exchange ratio over time, whereas high-level paraplegia (T3-T5) had lower circulating norepinephrine, epinephrine and free fatty acids (Skrinar et al 1982, Gass and Camp 1987, Hooker and Wells 1990, Stallknecht et al 2001. The progressive increase in lipid metabolism in low-paraplegia that is not seen in those with high-paraplegia demonstrates the important role that increasing spinal sympathetic input plays in endurance-based exercise (Thompson et al 2012).…”