High-Intensity Cycling Training Necessitates Increased Neuromuscular Demand of the Vastus Lateralis During a Fatiguing Contraction

ABSTRACT

Purpose: To examine the effects of a 5-week continuous cycling training intervention on electromyographic amplitude (EMG_RMS)- and mechanomyographic amplitude (MMG_RMS)-torque relationships of the vastus lateralis (VL) during a prolonged contraction. Methods: Twenty-four sedentary, young adults performed maximal voluntary contractions (MVCs) and a prolonged isometric trapezoidal contraction at the same absolute 40% MVC for the knee extensors before (PRE) and after training (POST_ABS). Individual b- (slopes) and a-terms (y-intercepts) were calculated from the log-transformed electromyographic amplitude (EMG_RMS)- and mechanomyographic amplitude (MMG_RMS)-torque relationships during the increasing and decreasing segments of the trapezoid. EMG_RMS and MMG_RMS was normalized for the 45-s steady torque segment. Results: At PRE, b-terms for the EMG_RMS-torque relationships during the linearly decreasing segment were greater than the increasing segment (p < .001), and decreased from PRE to POST_ABS (p = .027). a-terms were greater during the linearly increasing than decreasing segment at PRE, while the a-terms for the linearly decreasing segment increased from PRE to POST_ABS (p = .027). For the MMG_RMS-torque relationships, b-terms during the linearly decreasing segment decreased from PRE to POST_ABS (p = .013), while a-terms increased from PRE to POST_ABS when collapsed across segments (p = .022). Steady torque EMG_RMS increased for POST_ABS (p < .001). Conclusion: Although cycling training increased aerobic endurance, incorporating resistance training may benefit athletes/individuals as the alterations in neuromuscular parameters post-training suggest a greater neural cost (EMG_RMS) and mechanical output (MMG_RMS) to complete the same pre-training fatiguing contraction.

KEYWORDS:

• Electromyography
• endurance training
• fatigue
• mechanomyography
• motor unit
• vastus lateralis

Acknowledgments

We would like to thank P.R. Maier and J.D. Lippman who aided in data collection and analysis, as well as each subject for their selfless participation.

Disclosure statement

No potential conflict of interest was reported by the author(s).

IRB approval

This study was approved by the University’s institutional review board for human subject’s research.

Additional information

Funding

This publication was made possible by a National Strength and Conditioning Association Foundation (NSCAF) Graduate Research Doctoral Grant [FND0074499] and a University of Kansas Doctoral Student Research Fund (DSRF) grant.