Lower Extremity Biomechanical Changes Associated With Symmetrical Torso Loading During Simulated Marching

Abstract

The dose-response relationship between biomechanical variables and the magnitude of external loads is unclear. The use of different load distributions (e.g., pack types) may confound results because of changes in torso center of mass. Therefore, we examined the relationship between load magnitude and sagittal plane lower extremity mechanics of Soldiers walking with two symmetrically distributed loads. Fourteen Soldiers marched on a force-sensing treadmill at 1.34 m/s for 10 minutes with no load (BW_00) and while wearing vest-borne loads of 15 kg (BW_15) and 55 kg (BW_55). The effects of the loads on sagittal plane joint angles and moments were compared using 1-way repeated measures analyses of variance. Compared with BW_00, knee extension moment increased with the 15- and the 55-kg loads (both p < 0.003), confirming previously reported load-related biomechanical responses. Knee moment increases during early stance appeared to be the primary means by which the lower extremity counteracted BW_15 during early stance; in contrast, hip extensors and ankle dorsiflexors appeared to be the primary muscular efforts responsible for propulsion during late stance. Findings elucidated the effects of load magnitude on lower extremity mechanics without postural changes that result from pack-related shifts in torso center of mass.

Biomechanical Profiles When Towing a Sled and Wearing a Weighted Vest Once Cleared for Sports Post–ACL Reconstruction

“…15,22 Our findings of reduced KEM in the ACLR limb are consistent with compensatory gait patterns present after ACL rupture, 4,6,13,20 ACLR, 3-5 physical therapy, 19 and several years after ACLR. 19 Reduced KEM in the ACLR limb is found across multiple functional tasks such as step ups, running, and drop jump landing, implicating the robustness of this biomechanical profile in the ACLR limb.…”

Influence of a 12.8-km military load carriage activity on lower limb gait mechanics and muscle activity

“…The quadriceps muscles act eccentrically during early stance to control knee flexion, whilst the plantar flexors act concentrically towards the end of stance to contribute to push-off Seay et al 2014). The increased gastrocnemius lateralis muscle activity suggests a greater plantar flexor force production was required for push-off when carrying a load of 35.5 kg, consistent with earlier findings which reported an increase in gastrocnemius activity with loads up to 33 kg .…”

Sex Differences in Lower Limb Biomechanics During a Single-Leg Cut with Body Borne Load

“…While load reportedly failed to produce any kinematic adaptations at the hip or knee, the addition of 20 and 40 kg body borne loads resulted in an increase of external flexion moments at both joints while running 18 . These extended limb postures when paired with high magnitude moments may prevent limb collapse, but further increase strain on the musculoskeletal system by aiding the transfer of high ground reaction forces up the kinetic chain of the body 25 . Further, high magnitude moments are indicative of an increase in mechanical work of the musculoskeletal system that occurs in an effort to prevent limb collapse.…”

“…During a single-leg cut with body borne load, Brown et al 14 reported that military personnel exhibited a significant increase in peak hip and knee flexion, and hip adduction joint moments to successfully complete the maneuver. These elevated joint moments require greater force generation by the hip and knee musculature to prevent collapse of the limb, but increase the stresses placed on the musculoskeletal system and risk of injury 25,26,27 . Yet, to date, it is unknown if military personnel exhibit similar adaptations in lower limb biomechanics, and subsequent increased risk of musculoskeletal injury, when performing a single-leg cut with the small incremental changes of body borne load commonly worn during military related tasks (i.e.…”

“…During a single-leg cut with body borne load, Brown et al 14 reported that military personnel exhibited a significant increase in peak hip and knee flexion, and hip adduction joint moments. These elevated joint moments require greater force generation by the hip and knee musculature to prevent collapse of the limb, but increase the stresses placed on the musculoskeletal system and risk of injury 25 . Both large knee flexion, with an extended knee 26 , and abduction moments reportedly strain the soft-tissue structures of the joint 27 35 or Silder et al 36 reported a significant difference in lower limb biomechanics between male and female participants when walking with body borne load, despite the fact females reportedly exhibit a sex dimorphism in hip and knee biomechanics during unloaded walking [37][38][39] .…”