Experimental estimation of energy absorption during heel strike in human barefoot walking

Abstract

Metabolic energy expenditure during human gait is poorly understood. Mechanical energy loss during heel strike contributes to this energy expenditure. Previous work has estimated the energy absorption during heel strike as 0.8 J using an effective foot mass model. The aim of our study is to investigate the possibility of determining the energy absorption by more directly estimating the work done by the ground reaction force, the force-integral method. Concurrently another aim is to compare this method of direct determination of work to the method of an effective foot mass model. Participants of our experimental study were asked to walk barefoot at preferred speed. Ground reaction force and lower leg kinematics were collected at high sampling frequency (3000 Hz; 1295 Hz), with tight synchronization. The work done by the ground reaction force is 3.8 J, estimated by integrating this force over the foot-ankle deformation. The effective mass model is improved by dropping the assumption that foot-ankle deformation is maximal at the instant of the impact force peak. On theoretical grounds it is clear that in the presence of substantial damping that peak force and peak deformation do not occur simultaneously. The energy absorption results, due the vertical force only, corresponding to the force-integral method is similar to the results of the improved application of the effective mass model (2.7 J; 2.5 J). However the total work done by the ground reaction force calculated by the force-integral method is significantly higher than that of the vertical component alone. We conclude that direct estimation of the work done by the ground reaction force is possible and preferable over the use of the effective foot mass model. Assuming that energy absorbed is lost, the mechanical energy loss of heel strike is around 3.8 J for preferred walking speeds (≈ 1.3 m/s), which contributes to about 15–20% of the overall metabolic cost of transport.

Walking with added mass magnifies salient features of human foot energetics

“…When the COP was underneath the hindfoot, which coincided with the first ∼40% of stance, negative work done during this phase accounted for ∼41% of the total negative work during the entire stance phase. The magnitude of net work after heel strike during unloaded walking (−2.988 J or −0.036 J kg −1 per stance) is similar to the values reported in a prior study in human walking of −3.8 J (Baines et al, 2018). Walking with +30% added mass further increased the foot's energy loss up to −3.476 J (−0.043 J kg −1 ) of net work.…”

Does the Heel’s Dissipative Energetic Behavior Affect Its Thermodynamic Responses During Walking?

“…Our results showed that walking for 10 min with +30% added mass increased the magnitude of net-negative work that the heel dissipates by 326.94 ± 379.92 J ( p = 0.005; Figure 2 ) and increased the heel’s temperature change by 0.72 ± 1.91 ( p = 0.009; Figure 3 )—findings that confirmed our first hypothesis. These findings confirm prior studies suggesting heel’s dissipative behavior ( Gefen et al, 2001 ; Takahashi et al, 2017 ; Baines et al, 2018 ; Honert and Zelik, 2019 ; Papachatzis et al, 2020 ) and that its temperature increases when walking for extended periods ( Hall et al, 2004 ; Yavuz et al, 2014 ; Reddy et al, 2017 ). However, we found no significant correlation between the heel’s temperature increase and the magnitudes of net-negative work ( p = 0.277; Figure 4 )—a finding that refuted our second hypothesis.…”

“…For instance, a large portion of energy dissipation (i.e., net-negative work) occurs immediately after the collision of the human heel with the ground. ( Gefen et al, 2001 ; Chi and Schmitt, 2005 ; Takahashi et al, 2017 ; Baines et al, 2018 ; Honert and Zelik, 2019 ; Papachatzis et al, 2020 ). Such net-negative collision work is a vital feature of walking as the legs transition from one step to the next ( Donelan et al, 2002a ; Donelan et al, 2002b ; Kuo, 2002 , 2007 ; Kuo et al, 2005 ; Kuo and Donelan, 2010 ).…”

Adaptations for bipedal walking: Musculoskeletal structure and three-dimensional joint mechanics of humans and bipedal chimpanzees (Pan troglodytes)

“…Although the metabolic cost of performing negative muscle fiber work is low (Woledge et al, 1985), energy dissipation through soft tissue deformations has no cost at all. As an example, a human-like heel strike permits mechanical energy dissipation via the heel pad (e.g., Baines et al, 2018; Honert and Zelik, 2019), rather than muscle-tendon lengthening. The shift from facultative to habitual bipedal walking in hominin evolution may have increased our reliance on soft (non-muscular) tissues for mechanical energy dissipation, which may have some metabolic and fatigue-resistance benefits in walking overall.…”