Substrate utilization during arm and leg exercise relative to the ventilatory threshold in men.
ABSTRACT The purpose of this study was to determine variations in substrate utilization in men during arm and leg exercise at 70 and 90% of mode specific ventilatory threshold (Tvent).
Ten males served as subjects. Limb total and muscle volumes were estimated in the right arm and leg with anthropometry. Ventilatory equivalence, excess CO2, and modified V-slope methods were used to determine Tvent. Subjects performed 15 min of exercise at 70 and 90%Tvent arm cranking (AC) exercise, and 70 and 90%Tvent leg cycling (LC) exercise.
VO2, VE, and HR were higher during LC exercise at both intensities. However, arm and leg RPE were not different at 70 and 90%Tvent. There were no significant differences between modes at 70%Tvent in relative carbohydrate use (54.5+/-9.5 and 57.8+/-8.2% for AC and LC, respectively) and relative fat oxidation (45.5+/-9.5 and 42.2+/-8.2% for AC and LC, respectively). However, at 90%Tvent, relative carbohydrate oxidation was significantly higher during AC versus LC exercise (75.4+/-10.6 versus 68.6+/-9.0%, p<0.05). Energy expenditure (total kJ x min(-1) was significantly lower during AC exercise (14.5+/-2.9 and 18.4+/-3.4 for the 70 and 90%Tvent, respectively) versus LC exercise (27.1+/-3.3 and 34.8+/-4.1 for the 70 and 90%Tvent, respectively; p<0.05).
These results indicate that substrate use during AC exercise is similar to LC exercise at 70%Tvent. However, as the exercise intensity increases, the smaller arm musculature becomes more dependent on carbohydrate utilization compared to the legs.
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ABSTRACT: In an incremental exercise the heart (HR) and stroke (SR) rates can be periodically synchronized suggesting that changes in the course of a relationship between power output (PO) and HR, recorded in the Conconi test as the deflection point (DP), may be related to changes in SR. In view of this, the aim of the present study was to analyse the course of the PO/HR, PO/SR, and SR/HR relationships in the progressive incremental exercise as well as to evaluate the accuracy of determination of anaerobic threshold (AT) based on the above three relationships. In the investigation, 12 kayakers performed the following tests on a special ergometer: the Conconi test (CT), the 30-min test (PET) with power output at DP (PO DP), the critical power test (CP), and the graded exercise test until exhaustion (GT), in which power output at the anaerobic threshold (PO AT4 , PO Dmax) was determined based on the blood lactate level (LA). The lack of DP in the PO/HR and the PO/SR relationships was detected in two and one athlete, respectively. In contrast, in the SR/HR relationship DP was recorded in all the tested subjects. The times of occurrence of DP did not significantly differ. Although, as judged by the LA dynamics in PET, the intensity of exercising exceeded that at the maximal lactate steady state (MLSS), all the athletes managed to complete the test. No significant differences were detected between PO DP and PO AT4 , PO Dmax or CP, and the agreement of the results obtained in CT with those collected in CP and GT was similar to that determined within each of the tests. The obtained results suggest that the changes in the course of the PO/HR relationship may be associated with spontaneous changes of SR. The lack of diversity among the times of occurrence of DP in the three relationships tested allows for an easy and non-invasive determination of AT even in case of a linear PO/HR relationship. The power output estimated with use of the presented method is higher than that at MLSS, but it is sustainable for at least 30 min. The accuracy of determination of anaerobic threshold based on the analysis of the three DPs appears to be comparable with that obtained with use of AT4, Dmax, and CP.
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ABSTRACT: Energy expenditure (EE) and fat oxidation in handbike cycling compared to cycling in order to determine the intensity that elicits maximal fat oxidation in handbike cycling. To establish the exercise intensity with the highest fat oxidation rate in handbike cycling compared with cycling (control group) in order to give training recommendations for spinal cord-injured (SCI) athletes performing handbike cycling. Institute of Sports Medicine, Swiss Paraplegic Centre, Nottwil, Switzerland. Eight endurance-trained handbike cyclists (VO2 peak(handbike cycling) 37.5+/-7.8 ml/kg/min) and eight endurance trained cyclists (VO2 peak(cycling) 62.5+/-4.5 ml/kg/min) performed three 20-min exercise blocks at 55, 65 and 75% VO2 peak in handbike cycling on a treadmill or in cycling on a cycling ergometer, respectively, in order to find the intensity with the absolutely highest fat oxidation. The contribution of fat to total EE was highest (39.1+/-16.3% EE) at 55% VO2 peak in handbike cycling compared to cycling, where highest contribution of fat to EE (50.8+/-13.8%) was found at 75% VO2 peak. In handbike cycling, the highest absolute fat oxidation (0.28+/-0.10 g/min) was found at 55% VO2 peak compared to cycling, where highest fat oxidation (0.67+/-0.20 g/min) was found at 75% VO2 peak. Well-trained handbike cyclists have their highest fat oxidation at 55% VO2 peak(handbike cycling) compared to well-trained cyclists at 75% VO2 peak(cycling). Handbike cyclists should perform endurance exercise training at 55% VO2 peak(handbike cycling), whereas well-trained cyclists should be able to exercise at 75% VO2 peak(cycling). For training recommendations, the heart rate at 55% VO2 peak(handbike cycling) lies at 135+/-6 bpm in handbike cycling in SCI compared to 147+/-14 bpm at 75% VO2 peak(cycling) in well-trained cyclists. We presume that the reduced muscle mass involved in exercise during handbike cycling is the most important factor for impaired fat oxidation compared to cycling. But also other factors as fitness level and haemodynamic differences should be considered. Our results are only applicable to well-trained handbike cyclists with SCI and not for the general SCI population.Spinal Cord 11/2004; 42(10):564-72. DOI:10.1038/sj.sc.3101612