Effects of prolonged walking with body borne load on knee adduction biomechanics.
Micah D Drew, Samantha M Krammer, Tyler N Brown
PMID 33360641WHAT IT FOUND
Carrying 30 kg increased knee adduction moment by 37%, a magnitude linked to osteoarthritis risk.
Walking for 60 minutes increased knee adduction angle by 24%. Neither load nor duration changed biomechanical variability. These findings suggest military load carriage stresses the medial knee.
Key findings
01Walking with a 30 kg load increased peak knee adduction moment by approximately 37% compared to no load.
02Walking for 60 minutes increased peak knee adduction angle by 24% and range of motion by 17%, regardless of load.
03Neither added load nor walking duration significantly affected the variability of knee adduction biomechanics.
STILL TO COME
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What it does not show
Small sample size (13 participants) limits generalizability. Participants were healthy, recreationally active adults, not soldiers with existing musculoskeletal issues or specific military training backgrounds. The load was applied symmetrically via a vest, whereas military loads are often asymmetric (e.g., rucksacks), which may alter biomechanics differently. The 60-minute walk may not have been sufficient to induce the level of fatigue experienced in actual military training. Participants were not required to have prior load carriage experience.
Declared interests
The authors declared no conflicts of interest. The work was supported by the National Institutes of Health (Extramural).
The easy way to misread this
Do not assume that walking duration causes the same biomechanical stress as heavy loading. The study found that load primarily affected knee adduction moment (KAM), while duration affected knee adduction angle (KAA). These are distinct biomechanical variables, and the mechanisms of injury risk may differ.