Abstract
BackgroundA better understanding of lower-extremity muscles’ activation patterns and joint kinematics during different workloads could help rehabilitation professionals with prescribing more effective exercise regimen for elderly and those with compromised muscles. We examined the relative contribution, as well as activation and co-activation patterns, of lower-extremity muscles during semi-reclined cycling at different workloads during a constant cadence.MethodsFifteen healthy novice cyclists participated at three 90-second cycling trials with randomly assigned workloads of 0, 50, and 100 W, at a constant cadence of 60 rpm. During all trials, electromyograms were recorded from four lower-extremity muscles: rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius medialis (GT). Joint kinematics were also recorded and synchronized with the EMG data. Muscle burst onset, offset, duration of activity, peak magnitude, and peak timing, as well as mean joint angles and mean ranges of motion were extracted from the recorded data and compared across workloads.ResultsAs workload increased, BF and TA displayed earlier activations and delayed deactivations in each cycle that resulted in a significantly (p < 0.05) longer duration of activity at higher workloads. RF showed a significantly longer duration of activity between 0 and 50 W as well as 0 and 100 W (p < 0.05); however, the activity duration of GT was not appeared to be affected significantly by workload. EMG peak-magnitude of RF, BF, and TA changed significantly (p < 0.05) as workload increased, but no changes were observed in the EMG peak-timing across workloads. Durations of co-activation in the RF-BF pair as well as the RF-TA pair increased significantly with workload, while the RF-TA and TA-GT pairs were only significantly different (p < 0.05) between the 0 and 100 W workload levels. Increased workload did not lead to any significant changes in the joint kinematics.ConclusionsMuscles’ activity patterns as well as co-activation patterns are significantly affected by changes in cycling workloads in healthy individuals. These variations should be considered during cycling, especially in the elderly and those with compromised musculoskeletal systems. Future research should evaluate such changes specific to these populations.Electronic supplementary materialThe online version of this article (doi:10.1186/1743-0003-11-146) contains supplementary material, which is available to authorized users.
Highlights
A better understanding of lower-extremity muscles’ activation patterns and joint kinematics during different workloads could help rehabilitation professionals with prescribing more effective exercise regimen for elderly and those with compromised muscles
Studies have shown that the positioning such as seat height, crank’s arm length, and foot position in which an individual cycles could affect the biomechanical efficacy of the cycling [7,8]
The analysis of the International Physical Activity Questionnaire (IPAQ) responses revealed that on average, participants were considered moderately active with a median IPAQ score of 1522.50 MET (Metabolic Equivalent of Task) min/week [13]
Summary
A better understanding of lower-extremity muscles’ activation patterns and joint kinematics during different workloads could help rehabilitation professionals with prescribing more effective exercise regimen for elderly and those with compromised muscles. The cycling exercise potentially minimizes the stress on the joints when compared to weight bearing exercises and could have beneficial effects on mobility and functional abilities in performing daily activities [1,6]. It could further improve muscle strength, power, and joints’ ranges of motion, while providing significant cardiovascular benefits [1]. Recumbent cycling has been recommended as the better choice due to less stress on the joints and muscles and its more comfortable platform [3,6]
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