Muscular Changes Resulting from Pole Use in Loaded Downhill Walking

Abstract

PURPOSE:Walking poles have emerged as popular aides to use while hiking and backpacking. Previously it has been shown that poles are effective in reducing joint forces and moments, with and without load carriage (Bohne, Abendroth-Smith & Heise, 2005). However, the effects of pole use on lower extremity muscle activity, during load carriage, has not been examined in relation to joint moments. In this study, the effectiveness of walking poles during downhill hiking while carrying a loaded internal frame backpack was examined for relative muscle activity in the lower extremity. METHODS:Thirteen male participants walked an 8m ramp with a downhill grade of 20 degrees (36%), while wearing no pack, a daypack and an expedition pack (15% or 30% BW, respectively). Aforce plate was located on the downhill portion of the ramp (2.5m from the top of ramp). The participants walked with poles and without poles for every pack condition (2x3 repeated measures design), in a random order of conditions. Walking speed was held constant for all subjects (3 mph or 1.34m/s ± 5%). Surface EMG electrodes were placed on the vastus lateralis (VL), rectus femoris (RF), and biceps femoris (BF) of the leg striking the force plate. EMGs were rectified, filtered, and integrated (IEMG) during the stance phase on the force plate. Joint moments were calculated and previously reported but are noted here for comparison to muscle activity. RESULTS:The results demonstrated decreasing joint moments with pole use (in comparison to no poles) for all pack conditions (ankle=14.61%, knee = 10.00%, and hip = 13.48%). Activity of all muscles were reduced while using poles with the expedition pack (7.00%, ES = .59). However, when examining pole use across all pack conditions, only the BF activity consistently decreased (4.65%, ES = .82). Muscle use actually increased for the day pack with poles (6.29%, ES = .68), while on average, muscle use did not change with no pack condition, in terms of pole use (<1%, ES = .10). CONCLUSIONS: The changes observed in muscle activity may indicate two different poling strategies are being utilized during loaded walking. The pole use with day packs may be used more for balance while during the expedition pack condition the poles may be used to aid in 'unweighting' the joints, and is believed to reduce some stress on the muscles. The results demonstrate that while pole use reduces joint forces and moments in loaded downhill walking, muscle activity may not be lessened. Bohne, M., Abendroth-Smith, J., & Heise, G. H. (2005) The Effects of hiking downhill using two trekking poles while carrying an external load in a backpack. ISB /ASB Congress proceedings, pp. 970