Objective: To examine the effect of contraction frequency on energy expenditure and substrate utilisation during upper (UE) and lower (LE) body exercise. Methods: Twenty four college students were recruited: 12 were tested on an arm ergometer, and the other 12 were tested on a leg ergometer. Each subject underwent three experimental trials on three separate days, and the three trials were presented in a randomised order. Each trial consisted of 10 minutes of arm cranking or leg cycling at 40, 60, or 80 rev/min, with power output being kept constant at 50 W. Steady state oxygen uptake (VO 2 ) and respiratory exchange ratio (RER) were measured during each exercise. Energy expenditure was calculated from the steady state VO 2 adjusted for substrate metabolism using RER. Carbohydrate and fat oxidation were calculated from VO 2 and RER based on the assumption that protein breakdown contributes little to energy metabolism during exercise. Results: Energy expenditure was greater (p,0.05) at 80 rev/min than at 40 rev/min. No difference was found between 40 and 60 rev/min and between 60 and 80 rev/min during both UE and LE. During LE, carbohydrate oxidation was also higher at 80 rev/min than at 40 rev/min, whereas no difference in fat oxidation was found among all three pedal rates. During UE, no speed related differences in either carbohydrate or fat utilisation were observed. Conclusions: Pedalling at a greater frequency helped to maximise energy expenditure during exercise using UE or LE despite an unchanging power output. Whereas contraction frequency affects energy expenditure similarly during both UE and LE, its impact on carbohydrate utilisation appears to be influenced by exercise modality or relative exercise intensity. P ower output of any given activity is determined by both the speed at which movement takes place and the force that is generated by the exercising muscle. One can maintain a constant power output even when speed is varied. However, despite an unchanging power output, a change in speed and thus force has been shown to affect many physiological responses including metabolic efficiency, [1][2][3][4][5][6][7] oxygen deficit, 8 lactate threshold, 9 and aerobic capacity. 8Much of the pertinent literature has been related to movement economy or athletic performance. Whether a change in speed would affect patterns of energy expenditure and substrate utilisation has not been thoroughly investigated. This is an intriguing question given that some commonly used exercise ergometers are equipped with a servo mechanism with which speed of movement can be selected without a concurrent change in workload. Cycling at a higher pedal rate has been considered to not only recruit more motor units, but also elicit a higher concentration of blood lactate despite an unchanging workload. 9 In this context, it may be speculated that more energy would be expended and carbohydrate used if exercise were performed at a fast velocity concomitant with less muscular tension. This hypothesis, however, remains to be tested, as Ha...

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This study examined the relation between pedal frequency and cardiovascular responses during arm (AE) and leg (LE) ergometry. Twenty-six subjects completed three experimental sessions. Each session consisted of 10 min of steady-state exercise on AE or LE at 40, 60, or 80 rev⋅min −1 . Oxygen uptake (VO 2 ) and cardiac output (Q) were measured during each exercise. Arteriovenous oxygen difference (a-vO 2 diff) was calculated by dividing VO 2 by Q. VO 2 was greater at 80 than at either 40 or 60 rev ⋅min −1 during both AE and LE. Q was greater at 60 than 40 rev ⋅min −1 during AE and at 80 than 40 rev⋅min −1 during LE. a-vO 2 diff was greater at 80 than 40 or 60 rev⋅min −1 during AE, but remained unchanged during LE. It appears that the greater VO 2 at 80 rev⋅min −1 during AE is due to an increase in peripheral O 2 extraction. However, an enhanced systemic circulation may be the principal cause for the greater VO 2 seen at 80 rev⋅min −1 during LE.

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