Force production in upper limb muscles could be affected following exercise that involves carrying a heavy backpack load. In lower limb muscles, previous study has demonstrated that there is muscle force depression after several different regimens of metabolically and mechanically demanding exercise. PURPOSE: The aim of this study is to examine pinch strength after exercising while carrying a heavy backpack with straps that compress the nerves and blood vessels of the upper limb. We hypothesized that backpack load carriage at 15% body weight and 30% body weight will lead to changes in upper limb lateral pinch strength as compared to a no-load condition. METHODS: To date, eleven participants (5 female, 6 male; mean ± SD of 25.8 ± 6.3 yrs, 81.9 ± 18 kg mass, 11 right handed) have completed 3 load conditions on separate days: 1) no backpack, 2) 15% body weight (BW) backpack, and 3) 30% BW backpack. Load condition order was randomized. Maximum lateral pinch strength was measured bilaterally using a pinch dynamometer before and after participants walked on a treadmill at 1.1 m/s for 30 minutes for each load condition. Pinch strength was measured every 5 minutes for 30 minutes after exercise. RMANOVA with Bonferroni post-hoc testing was used to compare among backpack conditions and among timepoints. RESULTS: Mean pinch strength on the dominant hand before backpack carriage was 10.8 ± 2.7 kg for male participants and 8.0 ± 1.2 kg for female participants. Pinch strength on the non-dominant hand before load carriage averaged 9.9 ± 1.7 kg for male participants and 7.5 ± 1.0 kg for female participants. Mean pinch strength on the dominant hand after 30% BW backpack carriage ranged from 10.6-10.9 kg for male participants and from 7.8 - 8.3 kg for female participants. There were no significant differences in pinch strength on either hand when comparing among backpack load conditions or timepoints for male or female participants. CONCLUSION: The compression of backpack straps and the exercise of walking with a backpack load did not affect pinch strength in the first 30 minutes after backpack carriage.
Lopez, Malea N.; Hein, Jennifer L.; Saul, Katherine; and Schmidt, Deanna J.
"The Effects of Heavy Backpack Carriage on Hand Strength,"
International Journal of Exercise Science: Conference Proceedings: Vol. 14:
3, Article 67.
Available at: https://digitalcommons.wku.edu/ijesab/vol14/iss3/67