VO2peak and the gas-exchange anaerobic threshold during incremental arm cranking in able-bodied and paraplegic men

Resting energy expenditure, peak oxygen uptake ((V)over dot O-2peak) and th e gas-exchange anaerobic threshold (Th-an) were measured during incremental arm cranking (15 W . min(-1)) in six able-bodied (AB) and six paraplegic ( P) subjects. Only male subjects with traumatic spinal cord injuries in the area of the 10-12th thoracic segment were included in the P group. All AB a nd P subjects were physically active. Mean (SE) values for age and body mas s were 28 (2) years and 78.9 (3.9) kg for the AB group and 32 (4) years and 70.8 (7.9) kg for the P group (P > 0.05). Resting energy expenditure value s were not found to be significantly different between AB [5.8 (0.2) kJ . m in(-1)] and P [5.1 (0.3) kJ . min(-1)] subjects. Mean (V)over dot O-2peak v alues were 29.3 (2.4) ml . kg(-1) . min(-1) and 29.6 (2.2) ml . kg(-1) . mi n(-1) for the AB and P groups, respectively (P > 0.05). Absolute oxygen upt ake values measured at two gas-exchange anaerobic threshold (Th-an) were no t significantly different between the two groups. However, the Th-an occurr ed at a significantly higher percentage of (V)over dot O-2peak in the P [58 .9 (1.7)%] group than in the AB [50.0 (2.8)%] group (P < 0.05). Moreover, r espiratory exchange ratio (R) values obtained at the Th-an and at 15, 45, 6 0, 75 and 90 W of incremental exercise were significantly lower in the P gr oup than in the AB group. Heart rates were significantly elevated at every submaximal work stage (15-120 W) in the P group compared to the AB group (P < 0.05). These findings suggest that chronic daily wheelchair activity pro duces local adaptations in the functional upper-body musculature, which red uce glycogenolysis and increase the rate of lipid utilization (lower R) dur ing arm exercise. These local adaptations may be in part responsible for th e significantly higher Th-an observed for arm exercise in P subjects, even though (V)over dot O-2peak values were essentially the same for both groups .