Lower Extremity Muscle Activation Differences Between Upright And Recumbent Cycling

Abstract

Due to the recent increase in popularity of the recumbent cycling position, both the standard upright (U) and recumbent (R) positions are readily available choices for exercise and rehabilitation. However, the altered orientation of the lower extremity relative to the line of gravity in the R compared to the U may affect the way the muscles are used/trained. PURPOSE The goal of this investigation was to determine the differences in muscle activations between the U and R cycling positions at a submaximal power level appropriate for rehabilitation or prolonged exercise. METHODS After obtaining university-approved informed consent and appropriate warm-up, 15 healthy college-aged men (age = 21.7 +/− 1.0 yrs, height = 1.80 +/− 0.08 m, mass = 76.4 +/− 11.8 kg) with U and R cycling familiarity were examined while cycling steady-state at 60 rpm and 90 W in each position (random order of testing). Max hipto-pedal distance (105% of floor to standing hip distance) and included angle between shoulder, hip, and bottom bracket (130°) were matched. The hip was level with the bottom bracket in the R position and 75° to the horizontal in the U position. Bipolar surface electromyography was recorded at 1000Hz on the tibialis anterior (TA), soleus (SO), gastrocnemius (GA), vastus lateralis (VL) and medialis (VM), rectus femoris (RF), hamstrings (HM), and gluteus maximus (GM). Signals from three consecutive pedal revolutions were rectified and averaged within 10% bins of the pedal revolution starting at top-dead-center. In order to match kinematics, R signals were shifted by the 75° difference in hip orientation. Statistical significance was evaluated at p <0.05. RESULTS Activation levels changed significantly within the pedal revolution for all muscles in both the U and R positions. However, activation level profiles were significantly different in trend between the U and R for all muscles except the TA and HM. Differences were observed in the propulsion phase (0–50% of pedal cycle) for the SO, GA, VL, VM, RF, and GM and in the recovery phase (50–100% of pedal cycle) for all muscles except for the TA. When the activation within the pedal revolution was examined in its entirety, there was a significant increase in the U relative to the R in the HM and a significant decrease in the SO, GA, and RF. CONCLUSION Based on these observed differences in muscle activation levels, there may be reason to choose one cycling position over another when specific muscles are being targeted/avoided. Acknowledgements: This research was supported by a grant from the Colorado Injury Control Research Center.