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Abstract

The Farmer’s Walk is a strength and conditioning exercise that emulates functional tasks in daily living and is frequently used in rehabilitation. It challenges total body strength, dynamic core stabilization, and grip strength. PURPOSE: To examine how load, carrying direction, strap use, and training status affect upper-body and trunk muscle activation during loaded carrying tasks. METHODS: Twelve participants (n=12) aged 18-30 years were enrolled in the study and separated into 3 groups based on weight lifting frequency: Training Group 0 (non-weightlifters), Training Group 1 (1-3x a week), and Training Group 2 (4-6x a week). Surface electromyography (EMG) was recorded from the anterior deltoid (AD), posterior deltoid (PD), upper trapezius (UT), pectoralis major (Pec), latissimus dorsi (Lat), teres major (TM), and erector spinae (ES) during forward and backwards walking performed at 50%, 75%, 100%, and 150% body weight using a hex trap bar. Additional trials of 100% and 150% body weight were performed using figure-8 lifting straps. We used linear mixed-effects models with subject as a random effect to evaluate the effects of weight, direction, strap condition, and training status on normalized muscle activation (%MVIC). Post hoc comparisons were performed using Tukey adjustment. RESULTS: We observed a significant Weight × Muscle interaction (p = .048), indicating that the effect of load differed among muscles. Upper trapezius activation increased disproportionately at 100% BW (β = 62.30, 95% CI [13.96, 110.65], p = .012) and 150% BW (β = 79.74, 95% CI [28.78, 130.70], p = .002) relative to 50% BW. Posterior deltoid and upper trapezius exhibited the greatest load-related increases in activation. Strap use produced a small but significant reduction in overall muscle activation (p = .009), whereas carrying direction had no significant effect (p = .787). A significant Training × Muscle interaction was identified (F(12, 887) = 3.86, p < .001). The untrained group showed greater AD and Pec activation, whereas the highly trained group (lifting 4 to 6 times per week) showed greater ES and Lat activation than the moderately trained group (lifting 1 to 3 times per week). CONCLUSION: Load-related increases in muscle activation were primarily observed in the shoulder musculature, particularly the upper trapezius and posterior deltoid. Strap use reduced overall muscular demand, whereas carrying direction had minimal influence. Training status altered muscle recruitment patterns, suggesting different load-carrying strategies among training groups.

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