Aftereffects of walking with a backpack load on grip strength and pinch strength

Backpack carriage is common in occupational settings, and this study examined whether grip and lateral pinch strength after walking differed according to backpack load, sex, and post-walking time. Thirty-eight participants (18 female) completed three randomized conditions consisting of 30 min of treadmill walking at 1.1 m/s with No Load, 15% body weight (BW) backpack, or 30% BW backpack. Grip and pinch strength were measured before walking (PRE), immediately POST after dropping the backpack, and then every 5 min for 25 min. In a baseline-adjusted linear mixed-effects model, grip strength showed a significant effect of post-walking Timepoint (F(5, 540) = 6.46, p < 0.001), but no main effect of Load (p = 0.735) or Sex × Load interaction (p = 0.664). Across conditions, grip strength was modestly lower immediately after walking than at PRE (−0.79 kg, 95% CI -1.45 to −0.13 kg) and subsequently increased during the 25-min post-walking observation period. The immediate PRE-to-POST reduction was not significant when each load condition was considered separately. Female participants showed a descriptive pattern of progressively greater immediate reductions with increasing load, but this pattern was not confirmed by the primary or non-parametric sensitivity analyses and was therefore considered exploratory. Pinch strength showed no load- or time-dependent effects. These findings indicate a small post-walking change in grip strength performance but do not establish that backpack load independently amplified this effect under the tested conditions. The data suggest that the timing of grip strength measurements could influence reported results.