Anthropometric characteristics and gait transition speed in human locomotion

Role of sex and stature on the biomechanics of normal and loaded walking: implications for injury risk in the military

Load carriage and marching 'in-step' are routine military activities associated with lower limb injury risk in service personnel. The fixed pace and stride length of marching typically vary from the preferred walking gait and may result in overstriding. Overstriding increases ground reaction forces and muscle forces. Women are more likely to overstride than men due to their shorter stature. These biomechanical responses to overstriding may be most pronounced when marching close to the preferred walk-to-run transition speed. Load carriage also affects walking gait and increases ground reaction forces, joint moments and the demands on the muscles. Few studies have examined the effects of sex and stature on the biomechanics of marching and load carriage; this evidence is required to inform injury prevention strategies, particularly with the full integration of women in some defence forces. This narrative review explores the effects of sex and stature on the biomechanics of unloaded and loaded marching at a fixed pace and evaluates the implications for injury risk. The knowledge gaps in the literature, and distinct lack of studies on women, are highlighted, and areas that need more research to support evidence-based injury prevention measures, especially for women in arduous military roles, are identified.

The effect of sex, stature, and limb length on the preferred walk-to-run transition speed

BACKGROUND

The preferred walk-to-run transition speed (PTS) for healthy adults is approximately 2 m∙s^-1, however, PTS is influenced by anthropometric factors. Yet despite known sex differences in anthropometrics, studies have reported no sex differences in PTS.

RESEARCH QUESTION

Do stature and limb length affect PTS in the same way for both male and female healthy adults?

METHODS

Thirty-seven (19 female) non-injured adults volunteered for this study. Participants completed a walk-to-run transition protocol, where the treadmill speed was increased from 1.2 m∙s^-1 to 2.2 m∙s^-1, in increments of 0.1 m∙s^-1 every two minutes. An independent t-test compared PTS between sexes. Multiple regression analysis determined the effect of sex and stature and sex and limb length on PTS.

RESULTS

Female participants transitioned at a lower PTS than male participants (1.8 (0.2) m∙s^-1 versus 1.9 (0.1) m∙s^-1; p ≤ 0.026). Sex and stature explained 19% of the variance in PTS, while sex and limb length explained 21% of the variance. Including interactions increased the variance explained by 23% and 2% for sex and stature and sex and limb length, respectively. The significant interaction between sex and stature showed PTS was inversely proportional to stature for male participants but directly proportional for female participants.

SIGNIFICANCE

These findings suggest that the extent to which stature and limb length influence the preferred transition speed may differ between sexes.

Relationship between kinematic gait parameters during three gait modifications designed to reduce peak knee abduction moment

PURPOSE

Gait modifications designed to change a single kinematic parameter have reduced first peak internal knee abduction moment (PKAM). Prior research suggests unintended temporospatial and kinematic changes occur naturally while performing these modifications. We aimed to investigate i) the concomitant kinematic and temporospatial changes and ii) the relationship between gait parameters during three gait modifications (toe-in, medial knee thrust, and trunk lean gait).

METHODS

Using visual real-time biofeedback, we collected 10 trials for each modification using individualized target gait parameters based on participants' baseline mean and standard deviation. Repeated measures ANOVA was performed to determine significant differences between conditions. Mixed effects linear regression models were then used to estimate the linear relationships among variables during each gait modification. All modifications reduced KAM by at least 5%.

RESULTS

Modifications resulted in numerous secondary changes between conditions such as increased knee abduction during toe-in gait and increased knee flexion with medial knee thrust. Within gait modifications, relationships between kinematic parameters were similar for toe-in gait and medial knee thrust (i.e. increased toe-in and decreased knee abduction), while increased trunk lean showed no relationship with any other kinematic parameters during trunk lean trials.

CONCLUSION

Two main mechanisms were found as a result of this investigation; the first being a pattern of toeing-in, knee abduction, flexion, and internal hip rotation, while trunk lean modification presented as a separate gait pattern with limited secondary changes. Future studies should consider providing feedback on multiple linked parameters, as it may feel more natural and optimize KAM reductions.

Biomechanics of the human walk-to-run gait transition in persons with unilateral transtibial amputation

Propulsive force production (indicative of intrinsic force-length-velocity characteristics of the plantar flexor muscles) has been shown to be a major determinant of the human walk-to-run transition. The purpose of this work was to determine the gait transition speed of persons with unilateral transtibial amputation donning a passive-elastic prosthesis and assess whether a mechanical limit of their intact side plantar flexor muscles is a major determinant of their walk-to-run transition. We determined each individual׳s gait transition speed (GTS) via an incremental protocol and assessed kinetics and kinematics during walking at speeds 50%, 60%, 70%, 80%, 90%, 100%, 120%, and 130% of that gait transition speed (100%:GTS). Unilateral transtibial amputees transitioned between gaits at significantly slower absolute speeds than matched able-bodied controls (1.73±0.13 and 2.09±0.05m/s respectively, p<0.01). Peak anterior-posterior propulsive force increased with speed in controls until 100% of the preferred gait transition speed and decreased at greater speeds. A significant decrease in anterior-posterior propulsive force production was found at 120%GTS (110%: 0.27±0.04>120%: 0.23±0.05BW, p<0.05). In contrast, amputee subjects' intact side generated significantly higher peak anterior-posterior propulsive forces while walking at speeds above their preferred gait transition speed (100%: 0.28±0.04<110%: 0.30±0.04BW, p<0.05). Changes in propulsive force production were found to be a function of changes in absolute speed, rather than relative to the walk-to-run transition speed. Therefore, the walk-to-run transition in unilateral transtibial amputees is not likely dictated by propulsive force production or the force-length-velocity characteristics of the intact side plantar flexor muscles.

Economical Speed and Energetically Optimal Transition Speed Evaluated by Gross and Net Oxygen Cost of Transport at Different Gradients

The oxygen cost of transport per unit distance (CoT; mL·kg^-1·km^-1) shows a U-shaped curve as a function of walking speed (v), which includes a particular walking speed minimizing the CoT, so called economical speed (ES). The CoT-v relationship in running is approximately linear. These distinctive walking and running CoT-v relationships give an intersection between U-shaped and linear CoT relationships, termed the energetically optimal transition speed (EOTS). This study investigated the effects of subtracting the standing oxygen cost for calculating the CoT and its relevant effects on the ES and EOTS at the level and gradient slopes (±5%) in eleven male trained athletes. The percent effects of subtracting the standing oxygen cost (4.8 ± 0.4 mL·kg^-1·min^-1) on the CoT were significantly greater as the walking speed was slower, but it was not significant at faster running speeds over 9.4 km·h^-1. The percent effect was significantly dependent on the gradient (downhill > level > uphill, P < 0.001). The net ES (level 4.09 ± 0.31, uphill 4.22 ± 0.37, and downhill 4.16 ± 0.44 km·h^-1) was approximately 20% slower than the gross ES (level 5.15 ± 0.18, uphill 5.27 ± 0.20, and downhill 5.37 ± 0.22 km·h^-1, P < 0.001). Both net and gross ES were not significantly dependent on the gradient. In contrast, the gross EOTS was slower than the net EOTS at the level (7.49 ± 0.32 vs. 7.63 ± 0.36 km·h^-1, P = 0.003) and downhill gradients (7.78 ± 0.33 vs. 8.01 ± 0.41 km·h^-1, P < 0.001), but not at the uphill gradient (7.55 ± 0.37 vs. 7.63 ± 0.51 km·h^-1, P = 0.080). Note that those percent differences were less than 2.9%. Given these results, a subtraction of the standing oxygen cost should be carefully considered depending on the purpose of each study.

Changes in the Preferred Transition Speed With Added Mass to the Foot

This study was conducted to investigate whether adding mass to subjects’ feet affects the preferred transition speed (PTS), and to ascertain whether selected swing phase variables (maximum ankle dorsiflexion angular velocity, angular acceleration, joint moment, and joint power) are determinants of the PTS, based upon four previously established criteria. After the PTS of 24 healthy active male subjects was found, using an incremental protocol in loaded (2 kg mass added to each shoe) and unloaded (shoes only) conditions, subjects walked at three speeds (60%, 80%, and 100% of PTS) and ran at one speed (100% of PTS) on a motor-driven treadmill while relevant data were collected. The PTS of the unloaded condition (2.03 ± 0.12 m/s) was significantly greater (P< .05) than the PTS of the loaded condition (1.94 ± 0.13 m/s). Within both load conditions, all dependent variables increased significantly with walking speed, decreased significantly when gait changed to a run, and were assumed to provide the necessary input to signal a gait transition, fulfilling the requirements of the first three criteria, but only ankle angular velocity reached a critical level before the transition, satisfying all four criteria to be considered a determinant of the PTS.