Lower Limb Muscle Activity Adjustment and Lactate Variation in Response to Increased Speed with Proportional Resistance in Young Adults

Martín G. Rosario* PT, PhD, CSFI, ATRIC, Daniel Heistand, SPT, Catie Lewis, SPT, Natalie Valdez, SPT, Matthew Nevarez, SPT, Mark Weber PT, PhD, ATC

Texas Woman’s University, Physical Therapy Program, Dallas Campus; Texas.

Background: Various pathologies require physiotherapists to adjust therapy interventions, some of which are to reducing joint loads while strengthening the lower extremity musculature. Tools such as a sled can be used to accomplish a small load with high-repetition-resistance exercises.

Purpose: This study examined the impact of pushing a sled with regulated resistance on lower limb muscle activation and fatigue while walking and running.

Methods: The neuromuscular activity of the tibialis anterior (TA) and gastrocnemius (GA) muscles of thirty-six young adults were recorded using surface electromyography (EMG) and lactate data from a Nova Biomedical Lactate Plus meter. The sled used was the XPO Trainer, which maintains a steady resistance proportional to the user regardless of the forces applied to accelerate the sled. Baseline lactate was collected and followed by one of three protocols: run, run-push (RP), or walk-push (WP). Each included three trials over a 40 ft distance, during which EMG data were collected per trial, whereas lactate was collected following the completion of the appointed task.

Results: Repeated measures ANOVAs were performed, showing a considerable increase (P<0.05) in lactate levels between the WP and RP groups. Pushing the sled at both WP and RP speeds demonstrated substantial (P<0.05) neuromuscular modifications, primarily in the TA, followed by the GA, in comparison to running.

Conclusion: Pushing a constant resistance sled provoked distinct modifications in the lower limb musculature associated with speed. Running while pushing the sled elicits a higher blood lactate response associated with a longer maximal amplitude and a shorter time for muscle recruitment in the GA and TA muscles, all indicative of endurance-oriented exercise.

Keywords: XPO Trainer, Lactate Levels, Fatigue, Low extremity musculature, Resistance Training, Sled Training. Constant Resistance

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How to cite this article:
Martín G. Rosario, Daniel Heistand, Catie Lewis, Natalie Valdez, Matthew Nevarez, Mark Weber. Lower Limb Muscle Activity Adjustment and Lactate Variation in Response to Increased Speed with Proportional Resistance in Young Adults. Internal Journal of Sports Medicine and Rehabilitation, 2021; 4:18. DOI: 10.28933/ijsmr-201-02-1005


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