Research Institution:
Laboratory of Exercise Physiology of Seoul National University
Researchers:
Method
The subjects were 9 healthy male college students, divided randomly
into 3 groups. We also prepared a bicycle ergometer, (Monark SISE,
Sweden) modified, to be loaded in both forward pedaling and backward pedaling.
The technician from MBI WORLD INDUSTRY CO. LTD., helped us to do that.
Each group member repeated 3 types of pedaling with the bicycle ergometer,
in different order. The first group performed forward pedaling, backward
pedaling, and then combined pedaling. The second group performed
backward pedaling, combined pedaling, and then forward pedaling.
The third group performed combined pedaling, forward pedaling, and then
backward pedaling respectively.
Each type of pedaling took 20 minutes with a load of 2.5kp (750kgm. 125watt), 50 rpm, and recovery intervals between each performance were held for 6 hours. For each of the 3 types of exercise, EMG analysis was done with vastus lateralis, biceps femoris anterior tibialis, and gastrocnemius muscles. Also, the expired gas was collected to calculate V02 and R with a gas analyzing system. Blood samples were taken for calculating lactate accumulation. With the V02 and R we calculated energy consumption (Kcal/min), and efficiency.
For data analysis we used a one-way ANOV A and Duncan's multiple range test by means of an SPSS/PC program.
EMG Analysis
Muscle recruitment patterns in lower extremities were analyzed qualitatively
by EMG, and appeared as shown in Fig 1. Vastus lateralis, Biceps femoris,
Anterior tibialis, Gastrocnemius were all activated in both forward pedaling
and backward pedaling. But Vastus lateral is contracted more forcefully
in backward pedaling than in forward pedaling. On the other hand, Biceps
femoris, the antagonist of Vastus lateralis contracted more forcefully
in forward pedaling than in backward pedaling. Anterior tibialis analysis
did not show a significant difference between forward and backward pedaling.
Gastrocnemius contracted more forcefully in forward pedaling than in backward
pedaling.
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Comment
With the results from EMG analysis, we were able to recognize that
muscle recruitment patterns in lower extremities were not the same between
forward pedaling and backward pedaling. It was concluded that agonist
muscles would be developed simultaneously by exerting those muscle forces
interchangeably, even though there were no statistically significant differences
in metabolic variables (VO2, energy consumption, efficiency) except lactate
accumulation. Lactate was highest and efficiency was lowest in backward
pedaling. This indicated that backward pedaling was the hardest method
of the 3 types of pedaling. This would be due to the unfamiliarity of backward
pedaling. Although the difference didn't show a statistical significance,
in combined pedaling VO2 and energy consumption was lowest, lactate accumulation
was comparatively low, and efficiency was highest.
With these results we could predict that combined pedaling by agonist and antagonist muscles exerting force interchangeably had an effect on delaying muscular fatigue, with VO2 and energy consumption being statistically the same.
In conclusion, we recommend combined pedaling be used for well balanced muscular development.