On a treadmill, intensity is determined when a runner sets the speed of the belt. The runner must then find a combination of stride rate and length that will equal the belt speed. When using a cycle ergometer nothing forces a rider to find a combination of pedaling rate and force on the pedal to match a set intensity. PURPOSE: The purpose of this study was to assess the ability of trained individuals to match the intensity of cycling on a stationary cycle ergometer with the intensity of running on a treadmill. METHODS: Seven participants (3 female, 4 male) who regularly run for fitness ran on a treadmill for 2 miles at a self-selected pace (mean = 3.18 ± 0.17m/s). Then each participant rode the same course on the stationary ergometer with the goal to match the intensity of the run. For the two activities, expired gases, heart rate (HR) and EMG (right leg: gluteus maximus, GMAX, lateral vastus, VAST, hamstrings, HAMS, and gastrocnemius, GAST) were collected. Integrated EMG (mV*s) was calculated to determine muscle activation. Two tailed t-tests were used to quantify the difference between variables of the two trials and correlations were calculated to determine relationships of muscle activity to performance and metabolic data. RESULTS: The average pedaling rate and step frequency, HR, and ventilatory rate (VE) were not statistically different between running and cycling, although HR and VE were lower in cycling (HR mean=7bpm, VE mean=6L/min). Average oxygen consumption, energy expenditure, METS and breaths per minute were significantly greater during running (mean = 2.89 L/min, 41.37 ml/kg/min, 13.57 kcal/min, 11.82 METS, 40.70 bpm) than cycling (mean = 2.51 L/min, 35.89 ml/kg/min, 11.62 kcal/min, 10.25 METS, 33.79 bpm) (p < 0.05). Total muscle activity during running was two times greater than cycling (p = 0.00) and each of the muscles were activated more in running (p < 0.05). In running, GAST (r=0.83, p = 0.02) and HAMS (r=0.90, p=0.01) contributed most to total muscle activity, QUAD (r=0.97, p=0.00) and GAST (r=0.82, p=0.03) were highly correlated to speed, and QUAD (r=0.78, p=0.04) was highly correlated with caloric expenditure and oxygen consumption. In cycling, all muscles related similarly to the total muscle activity, speed, caloric expenditure and oxygen consumption, thus muscle activity was shared by the four muscles. CONCLUSION: Based on metabolic data, this group was unable to match the intensity of pedaling with that of their self-selected running pace. Interestingly, they had very similar stride (mean = 79.1/min) and pedaling (mean = 78.3/min) rates. When asked to match intensities, these participants naturally selected a resistance on the bike that would permit them to pedal at the same frequency as running, but the resistance was not sufficient to produce enough power to match the intensity. Two participants are regular cyclists and they were better able to match intensities. For those two, for example, caloric expenditure was only 0.42 kcal/min less on the bike, while the other five averaged 2.03 kcal/min less. The majority of the participants lacked experience on the bike which may be why they were unable to freely match the two intensities. The mismatch of intensity has implications on fitness and injury recovery. The two muscle patterns and task demands are so different, that it is necessary for people to be familiar with the effect of resistance on the bike and not just match leg movement rates if the same intensity is desired for acquiring or maintaining fitness.

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