The overall objective of this pilot study is to establish the feasibility and methodological validity of using high-density surface electromyography to characterize motor unit behavior of the quadriceps under thermoneutral and locally cooled conditions, and to generate preliminary data to inform the design of a larger, hypothesis-driven study.
This randomized, cross-over pilot study will recruit 24 healthy young adults (12 men and 12 women) between the ages of 18 and 35 years. Participants will attend two in-person laboratory visits separated by a minimum of 48 hours. Visit 1 will include informed consent, eligibility confirmation, baseline assessments, and familiarization procedures. Visit 2 will include experimental testing under thermoneutral and cooled conditions.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
24
For the cold condition, an Aircast Thigh Pad (Aircast), connected to the Cryo Cuff IC cooler (DJO Global, Vista, California, USA) will be applied to the dominant thigh. The system circulates ice water maintained at approximately 10-15°C with intermittent compression. Cooling duration will be individualized based on mid-thigh skinfold thickness, consistent with published recommendations that account for the effect of subcutaneous tissue on intramuscular cooling9. Participants with a mid-thigh skinfold thickness of 0-10 mm will receive 10 minutes of cooling; those with a skinfold thickness of 11-20 mm will receive 25 minutes of cooling; those with a skinfold thickness of 21-30 mm will receive 40 minutes of cooling; and those with a skinfold thickness of 31-40 mm will receive 60 minutes of cooling. Participants will remain seated for the duration of the cooling treatment.
Department of Health and Exercise Science at Wake Forest University
Winston-Salem, North Carolina, United States
Motor Unit (MU) Yield
Number of unique motor units successfully identified (decomposed) from quadriceps HDsEMG recordings during maximal voluntary contractions (MVCs) under thermoneutral and cooled conditions.
Time frame: Immediately after the intervention
HDsEMG Decomposition Accuracy
Quality/accuracy of motor unit decomposition from quadriceps HDsEMG recorded during MVCs under thermoneutral and cooled conditions, based on decomposition quality metrics generated by the Delsys Neuromap Precision Decomposition III algorithm.
Time frame: Immediately after the intervention
Proportion of Analyzable MVC Trials
Percentage of MVC trials that yield HDsEMG data suitable for motor unit decomposition and analysis under thermoneutral and cooled conditions (successful decomposition and acceptable signal quality).
Time frame: Immediately after the intervention
Slope of MUAP-FR relationship
Slope of the linear regression relating MU firing rate to MU action potential amplitude during MVCs under thermoneutral and cooled conditions.
Time frame: Immediately after the intervention
Y-intercept of MUAP-FR relationship
Y-intercept of the linear regression relating MU firing rate to MU action potential amplitude during MVCs under thermoneutral and cooled conditions.
Time frame: Immediately after the intervention
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