Loaded forced-marching shifts mechanical contributions proximally and disrupts stride-to-stride joint work modulation in recruit aged women

Clothing and individual equipment for the female soldier: developing a framework to improve the evidence base which informs future design and evaluation

The development of inclusive equipment and clothing is a priority across national defence departments that are part of The Technical Cooperation Programme. As such, a collaborative effort has been established to inform the development of clothing and equipment for women. This invited review provides an overview of an ongoing collaborative project presented at the sixth International Congress on Soldiers Physical Performance. The purpose of this review was to summarise the outputs of scoping work conducted to inform the direction of future research programmes. The scoping work has recommended a framework, which includes improved objective metrics for assessment, standardised methods to characterise study participants and improved methods for characterising the system being evaluated. The longer-term research project aims to implement the framework so that the design of future equipment and clothing is optimised for all end users.

Running gait produces long range correlations: A systematic review

BACKGROUND

Walking and running are common forms of locomotion, both of which exhibit variability over many gait cycles. Many studies have investigated the patterns generated from that ebb and flow, and a large proportion suggests human gait exhibits Long Range Correlations (LRCs). LRCs refer to the observation that healthy gait characteristic, like stride times, are positively correlated to themselves over time. Literature on LRCs in walking gait is well known but less attention has been given to LRCs in running gait.

RESEARCH QUESTION

What is the state of the art concerning LRCs in running gait?

METHODS

We conducted a systematic review to identify the typical LRC patterns present in human running gait, in addition to disease, injury, and running surface effects on LRCs. Inclusion criteria were human subjects, running related experiments, computed LRCs, and experimental design. Exclusion criteria were studies on animals, non-humans, walking only, non-running, non-LRC analysis, and non-experiments.

RESULTS

The initial search returned 536 articles. After review and deliberation, our review included 26 articles. Almost every article produced strong evidence for LRCs apparent in running gait and in all running surfaces. Additionally, LRCs tended to decrease due to fatigue, past injury, increased load carriage and seem to be lowest at preferred running speed on a treadmill. No studies investigated disease effects on LRCs in running gait.

SIGNIFICANCE

LRCs seem to increase with deviations away from preferred running speed. Previously injured runners produced decreased LRCs compared to non-injured runners. LRCs also tended to decrease due to an increase in fatigue rate, which has been associated with increased injury rate. Lastly, there is a need for research on the typical LRCs in an overground environment, for which the typical LRCs found in a treadmill environment may or may not transfer.

Recruit-aged adults may preferentially weight task goals over deleterious cost functions during short duration loaded and imposed gait tasks

Optimal motor control that is stable and adaptable to perturbation is reflected in the temporal arrangement and regulation of gait variability. Load carriage and forced-marching are common military relevant perturbations to gait that have been implicated in the high incidence of musculoskeletal injuries in military populations. We investigated the interactive effects of load magnitude and locomotion pattern on motor variability, stride regulation and spatiotemporal complexity during gait in recruit-aged adults. We further investigated the influences of sex and task duration. Healthy adults executed trials of running and forced-marching with and without loads at 10% above their gait transition velocity. Spatiotemporal parameters were analyzed using a goal equivalent manifold approach. With load and forced-marching, individuals used a greater array of motor solutions to execute the task goal (maintain velocity). Stride-to-stride regulation became stricter as the task progressed. Participants exhibited optimal spatiotemporal complexity with significant but not meaningful differences between sexes. With the introduction of load carriage and forced-marching, individuals relied on a strategy that maximizes and regulates motor solutions that achieve the task goal of velocity specifically but compete with other task functions. The appended cost penalties may have deleterious effects during prolonged execution, potentially increasing the risk of musculoskeletal injuries.

The effect of external loads and biological sex on coupling variability during load carriage

BACKGROUND

Load carriage is a fundamental requirement for military personnel that commonly results in lower-limb injuries. Coupling variability represents a potential injury mechanism for such repetitive tasks and its unknown whether external loads and biological sex affect coupling variability during load carriage.

RESEARCH QUESTION

Is there a sex-by-load interaction during load carriage at self-selected walking speeds?

METHODS

Twenty-six participants (13 males, 13 females) completed three 10-minute treadmill-based trials wearing body-borne external load (0 %BM, 20 %BM, and 40 %BM) at load-specific self-selected walking speeds. A Vicon motion capture system tracked markers with a lower-body direct-kinematic model calculating sagittal-plane segment kinematics of the thigh, shank, and foot across 19 strides. Continuous relative phase standard deviation (CRPv) provided a measure of coupling variability for each coupling angle (Thigh-Shank and Shank-Foot). The CRPv for each load and sex was compared using statistical parametric mapping repeated measures ANOVA and paired t tests.

RESULTS

Significant sex-by-load interactions were reported for the Thigh-Shank coupling. Males demonstrated no significant load differences in CRPv, however, females displayed significantly higher CRPv in the 40 %BM than the 0 %BM condition. A significant main effect of load was observed in the Shank-Foot coupling, with the 40 %BM having significantly greater CRPv than the other load conditions.

SIGNIFICANCE

Both biological sex and external loads significantly affected CRPv during load carriage at self-selected walking speeds. Females demonstrated greater CRPv at the heavier loads, suggesting that the perturbation from the heavier mass increases coupling variability, which may also be amplified by a greater total passive load due to their relatively higher adipose tissue compared to males. The consistent CRPv in males suggests that higher relative loads may be required to change coupling variability. Collectively, these results suggest that external load affects the coupling variability of males and females differently, providing potential for injury screening and monitoring programs.

Putting your best weighted foot forward: Reviewing lower extremity injuries by sex in weighted military marching

LAY SUMMARY

International marching events, such as the Nijmegen Marches, have a prominent place in Canadian military history, and participation continues today. In the Dutch military, the load carriage requirements previously differed by sex, with men carrying 10 kilograms during the march and women carrying no weight. The Canadian delegation requires both male and female participants to carry 10 kilograms. This article examines the effect of this policy on possible injuries using a Gender-based Analysis Plus lens. Weight carriage should focus on anthropometric factors, not sex, which will allow for appropriate and equal increased stresses (weight) for march participants while minimizing injuries.