Uneven running: How does trunk‐leaning affect the lower‐limb joint mechanics and energetics?

Abstract

This study aimed to investigate the role of trunk posture in running locomotion. Twelve recreational runners ran in the laboratory across even and uneven ground surface (expected 10 cm drop-step) with three trunk-lean angles from the vertical (self-selected, ∼15°; anterior, ∼25°; posterior, ∼0°) while 3D kinematic and kinetic data were collected using a 3D motioncapture-system and two embedded force-plates. Two-way repeated measures ANOVAs (α = 0.05) compared lower-limb joint mechanics (angles, moments, energy absorption and generation) and ground-reaction-force parameters (braking and propulsive impulse) between Step (level and drop) and Posture conditions. The Step-by-Posture interaction revealed decreased hip energy generation, and greater peak knee extension moment in the drop-step during running with posterior versus anterior trunk-lean. Furthermore, energy absorption across hip and ankle nearly doubled in the drop-step across all running conditions. The Step main effect revealed that the knee and ankle energy absorption, ankle energy generation, ground-reaction-force, and braking impulse significantly increased in the drop-step. The Posture main effect revealed that, compared with a self-selected trunk-lean, the knee's energy absorption/generation, ankle's energy generation and the braking impulse were either retained or attenuated when leaning the trunk anteriorly. The opposite effects occurred with a posterior trunk-lean. In conclusion, while the pronounced mechanical ankle stress in drop-steps is marginally affected by posture, changing the trunk-lean reorganizes the load distribution across the knee and hip joints. Leaning the trunk anteriorly in running shifts loading from the knee to the hip not only in level running but also when coping with ground-level changes. Highlights. Changing the trunk-lean when running reorganizes the load distribution across the knee and hip joints. . Leaning the trunk anteriorly from a habitual trunk posture during running attenuates the mechanical stress on the knee, while the opposite effect occurs with a posterior trunk-lean, irrespective to the ground surface uniformity. . The effect of posture on pronounced mechanical ankle stress in small perturbation height during running is marginal. . Leaning the trunk anteriorly shifts loading from the knee to the hip not only in level running but also when coping with small perturbation height.

Leaning the Trunk Forward Decreases Patellofemoral Joint Loading During Uneven Running

“…Compared with the self-selected running posture, the hip moment was systematically higher and lower throughout the stance phase of both analyzed steps when leaning the trunk forward and backward, respectively (Figure 5). The finding that a forward-leaning trunk during running shifts mechanical demand from knee extensors to hip extensors has been mirrored in the previous studies (2,10,32,33). Given that the hip's contribution to sagittal plane total work is small (less than 15%) during the stance phase of running (17), a distal-to-proximal load shift by a forward TL during running can be an effective strategy to decrease PFJ stress .…”

“…This is significant because most running is performed outdoors and is essentially challenged by uneven terrain. Rather, forward trunk-leaning during running enforces a distal-to-proximal shift in lower-limb mechanical demands (2,(32)(33)(34). Hence, one can argue that such postural modification may be a safer strategy for running-related PFP management.…”

“…Increasing the running step rate diminishes the negative work performed at the hip and knee joints (14) or decreasing the step length can decrease PFJ stress (42,43). Similarly, postural modifications such as forward trunk-leaning seem effective in reducing PFJ stress (10,32,33), because trunk orientation during walking (18) or running (1,2,32,33) also significantly redistributes the mechanical demands of lower-limb joints. This is mainly because of changing the orientation (3) and position (28) of the ground reaction force vector relative to the lower-limb joints.…”

Posture-induced modulation of lower-limb joint powers in perturbed running

“…Participants first ran using their self-selected trunk inclination ( TI 0 ). For the low forward ( TI + ) and backward ( TI¯ ) conditions, participants were instructed to increase and decrease their trunk flexion angle, respectively, to their comfort while running on even or uneven tracks [ 2 , 11 ]. Additionally, for the high forward ( TI ++ ) trunk inclination, participants had their trunk angle visually compared to a cardboard template by a second examiner before the trials.…”

“…Preferred sagittal trunk inclination varies significantly among participants [ 3 , 6 ] and is influenced by factors such as speed of locomotion [ 7 ], age [ 8 , 9 ] or spinal deformities [ 10 ]. While uneven running is seemingly associated with modified biomechanics in the lower-limb joints (hip, knee, and ankle) [ 11 , 12 ], there is limited comprehension of their contribution to mechanical power and work demands in relation to trunk inclination when accommodating perturbations. Previous research suggests that the lower-limb joints adapt to specific gait patterns to meet mechanical demands.…”