Exploring the Effect of Wilderness Backpack Configurations on Biomechanical and Electromyographic Variables

Authors

Kennedy C. Nelson, California Polytechnic State University, San Luis ObispoFollow
Cody Soo, California Polytechnic State University, San Luis ObispoFollow
Benjamin McConnell, California Polytechnic State University, San Luis ObispoFollow
Christiane R. O'Hara, California Polytechnic State University, San Luis ObispoFollow
Scott J. Hazelwood, California Polytechnic State University, San Luis ObispoFollow

Abstract

As the number of participants in both occupational and recreational wilderness activities increases, there is a growing need for preventative injury intervention. Hiking has been associated with elevated risk of injuries in the knees, lower back, and ankles; and hiking with a pack exacerbates those effects. PURPOSE: The aim of this study was to assess the effect of backpack type on several kinetic, kinematic, and EMG variables during a step-up motion. The dependent variables were specifically chosen for their documented correlation with injury susceptibility. The data were intended to provide insight on future assessment of pack design for both recreational backpackers and wilderness firefighters. METHODS: Eight male participants were recruited to perform a step-up on a 33 cm platform under three conditions; no pack (NP), hotshot pack (HP), and backpacking pack (BP). Packs were loaded with 30% of the participants' body weight. A 12-camera motion capture system with 32 retro-reflective markers and force plates were used to assess pelvic tilt range of motion (ROM), ankle compressive forces, knee compressive forces, and ankle mediolateral forces. EMG sensors recorded activity of the rectus femoris (RF) and tibialis anterior (TA). Repeated measures ANOVA tests were run to assess any relationship between conditions. RESULTS: Peak values for ankle and knee compressive forces and ankle mediolateral forces were greater for both HP and BP compared to NP (p<0.001). Average ankle mediolateral forces were greater for the HP compared to NP and BP (p=0.04). Average ankle compressive forces were greater for BP compared to NP and HP (p=0.02). Pelvic tilt ROM was not significant (p>0.05). EMG activity indicated mean muscle activity was greater for HP and BP compared to NP (p<0.05). Peak rectus femoris activity followed the same pattern, however peak tibialis anterior readings were only significantly higher for the HP condition (p=0.03). CONCLUSION: These findings support previous work indicating load carriage contributes to increased peak and mean forces experienced by the lower extremities. The significant difference in peak TA activity under the HP condition compared to others suggests that the pack configurations may differ in their influence on balance, though further studies are necessary for any definitive conclusions.

Recommended Citation

Nelson, Kennedy C.; Soo, Cody; McConnell, Benjamin; O'Hara, Christiane R.; and Hazelwood, Scott J. (2024) "Exploring the Effect of Wilderness Backpack Configurations on Biomechanical and Electromyographic Variables," International Journal of Exercise Science: Conference Proceedings: Vol. 14: Iss. 4, Article 121.
Available at: https://digitalcommons.wku.edu/ijesab/vol14/iss4/121