The influence of step-down technique on lower extremity mechanics during curb descent

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Abstract

When stepping down from a curb, individuals typically make initial ground contact with either their rearfoot or forefoot. The purpose of this study was to compare vertical ground reaction forces, lower extremity mechanics, and intra-limb work distribution when individuals adopt a rearfoot technique vs. a forefoot technique, during simulated curb descent. Sixteen subjects stepped down from a platform with both a rearfoot and a forefoot technique. Vertical ground reaction forces and sagittal plane joint kinematics and kinetics were examined for the lead limb during the step-down task. Paired t-tests were used for comparison. Subjects demonstrated greater ankle joint power and negative work, and less hip joint power and negative work, with the forefoot technique vs. the rearfoot technique. Total lower extremity negative work was greater for the forefoot technique vs. the rearfoot technique. The percent contribution to the total negative work was greater for the ankle joint, and less for the hip and knee joints, with the forefoot technique vs. the rearfoot technique. The results of this study may provide insight into how curb descent technique can be modified to alter lower extremity loading.

Introduction

Community ambulation poses many challenges, including negotiating steps and curbs (Lord et al., 2010). Curb descent can be particularly bothersome for individuals with common overuse lower extremity conditions, such as patellofemoral pain, osteoarthritis, and Achilles tendinopathy (Hensor et al., 2015, Thomee et al., 1999). This is likely due to the relatively high degree of lower extremity loading during curb descent, compared to level walking (Kutzner et al., 2010). As a result, it is important to identify ways to reduce and/or redistribute lower extremity loading during curb descent, in order to potentially minimize symptom exacerbation for individuals with common lower extremity musculoskeletal conditions.

Changing an individual’s step-down technique is one potential way to alter their lower extremity loading during curb descent. In general, individuals typically adopt either a rearfoot technique or a forefoot technique when descending curbs of standard height (Gerstle et al., 2017, Moudy et al., 2020). With a rearfoot technique, individuals make initial ground contact with their heel, whereas with a forefoot technique, they make initial ground contact closer to their metatarsal heads.

At this time, we are only aware of three studies that have examined how step-down technique (rearfoot vs. forefoot) influences lower extremity mechanics during a curb descent task (Kluft et al., 2018, Moudy et al., 2020, van Dieën et al., 2008). In general, these studies have found that adopting a forefoot technique results in greater ankle loading and less knee loading, vs. adopting a rearfoot technique. In addition, van Dieën et al. (2008) found that individuals exhibited lower vertical ground reaction forces (vGRF) when adopting a forefoot technique, compared to when they adopted a rearfoot technique. In contrast, Moudy et al. (2020) found no differences in vGRFs when comparing individuals who naturally used a forefoot technique vs. those who used a rearfoot technique. Some factors that may have contributed to these inconsistent findings include variation in the study designs (natural step-down technique vs. contrived step-down techniques), step heights (Moudy et al. − 14 cm; van Dieen et al. − 10 cm) and statistical analysis approaches (Moudy et al. - waveform analysis approach; van Dieen et al. - compared discrete parameters). Considering the limited available literature on this topic and the inconsistencies in previously published findings, it appears that there is a need to continue to examine how step-down technique influences lower extremity mechanics during curb descent.

While previous studies have compared lower extremity mechanics when stepping down from a curb with a rearfoot technique vs. a forefoot technique, it may also be important to consider how step-down technique redistributes the work performed by the lower extremity joints. When stepping down from a step or curb, the lead limb must absorb energy to control the weight of the body (Singhal et al., 2014). Examining the negative joint power and work for the lead limb may help to determine how the lower extremity joints are acting eccentrically to control weight acceptance (Winter, 2009). In addition, the contribution from each of the lower extremity joints to the total negative work performed by the limb may provide insight into how step-down technique influences work distribution among the joints (Lenton et al., 2019, Montgomery and Grabowski, 2018, Williams et al., 2017).

The purpose of this study was to compare vertical ground reaction forces, lower extremity mechanics, and intra-limb work distribution when individuals adopt a rearfoot technique vs. a forefoot technique, during simulated curb descent. Considering the results of previous studies (Kluft et al., 2018, Moudy et al., 2020, van Dieën et al., 2008), we hypothesized that subjects would demonstrate greater ankle joint negative power and work, and less hip and knee joint negative power and work, when adopting a forefoot technique, compared to when they adopted a rearfoot technique. Accordingly, we anticipated that with the forefoot technique, the ankle’s contribution to the total lower extremity negative work would be greater, while the contributions from the hip and knee joints would be less, compared to when subjects adopted the rearfoot technique. We did not formulate a priori hypotheses with respect to any vGRF-related metrics or spatiotemporal parameters, due to the inconsistencies in the findings of previous studies. The results of this study may help to inform clinicians regarding how to best instruct patients to modify their step-down technique to alter and/or redistribute the loads placed on different joints/tissues.

Section snippets

Participants

Sixteen subjects (10 females, 6 males) participated in this cross-sectional study. In order to participate, individuals were required to be between 18 and 25 years of age and report a Tegner Activity Scale (Tegner and Lysholm, 1985) score of greater than 4/10, indicating that, at minimum, they were recreationally active in the 6 months prior to enrollment. Individuals were excluded from participating if they had a history of lower extremity surgery or major injury or had experienced any injury

Kinetic variables

Peak vGRFs were greater for the forefoot condition vs. the rearfoot condition (p < .001; 95% CI [0.1, 0.3]; ES = 1.3) (Table 1). There was no difference in time-to-peak vGRF between the conditions (p = .203; 95% CI [−6.5, 27.9]; ES = 0.3) (Table 1).

Peak ankle power (p < .001; 95% CI [3.3, 6.0]; ES = 2.7) and ankle negative work (p < .001; 95% CI [0.4, 0.7]; ES = 2.7) were greater for the forefoot condition vs. the rearfoot condition (Table 1). In contrast, peak hip power (p < .001; 95% CI

Discussion

The purpose of this study was to compare vertical ground reaction forces, lower extremity mechanics, and intra-limb work distribution when individuals adopt a rearfoot technique vs. a forefoot technique, during simulated curb descent. As hypothesized, subjects demonstrated greater negative ankle joint power and work when adopting a forefoot technique, compared to when they adopted a rearfoot technique. They also demonstrated less negative hip joint power and work with the forefoot technique.

Conclusion

Our findings indicate that adopting a forefoot technique during curb descent results in greater ankle joint power/work and less hip joint power/work, compared to when a rearfoot technique is adopted. These findings may inform clinicians about how to best instruct individuals with common lower extremity musculoskeletal conditions, regarding curb descent technique.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Tia Demers, Nicole Bednarz, and Kris Mitchell are students in the Physical Therapy Program at the University of Wisconsin - La Crosse.

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Tia Demers, Nicole Bednarz, and Kris Mitchell are students in the Physical Therapy Program at the University of Wisconsin - La Crosse.

Dr. Emily Gerstle is an Assistant Professor in the Department of Health and Human Performance at the University of Scranton.

Dr. Thomas Gus Almonroeder is an Assistant Professor in the Department of Health Professions at the University of Wisconsin - La Crosse.

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