Elsevier

Clinical Biomechanics

Volume 78, August 2020, 105088
Clinical Biomechanics

Lecture
Relationship between vertical ground reaction force and muscle strength while climbing stairs after total hip arthroplasty

https://doi.org/10.1016/j.clinbiomech.2020.105088Get rights and content

Highlights

  • Little is known about vGRF and muscle strength while climbing stairs after THA.

  • Climbing stairs depends on muscle strength in the hip extensors.

  • Climbing function improves with improved hip and knee extensor muscle strength.

Abstract

Background

Little is known about the relationship between vertical ground reaction force (vGRF) and muscle strength while climbing stairs after total hip arthroplasty (THA).

Methods

We investigated the relationship between muscle strength and vGRF during stair climbing in 21 women with THA. Differences in the time required to climb stairs and side-to-side differences in muscle strength and vGRF during climbing were examined at 6 and 12 months.

The relationship between climbing time and vGRF variables and that between vGRF and muscle strength were analyzed using Spearman's rank correlation coefficient at 6 and 12 months. First peak force (Fz1) was defined as the peak vGRF at heel strike normalized by body weight.

Findings

Climbing time was related to the time to Fz1 at 6 and 12 months post-THA (r = 0.50–0.64). At 6 months, time to Fz1 was related to the strength of muscles involved in hip extension in the operated limb (r = −0.46). At 12 months, time to Fz1 was related to the strength of muscles responsible for knee extension in the operated limb (r = −0.45).

Interpretation

At 6 months, climbing stairs depended on muscle strength in the hip extensors. Conversely, at 12 months, the functional recovery of knee extensors was important for transferring weight upward while climbing stairs. Therefore, to improve the climbing function of patients with THA, it is important to not only focus on the recovery of muscle strength in the hip extensors but also improve muscle strength in the knee extensors.

Introduction

Muscle strength deficits in hip and knee muscles persist for several years after total hip arthroplasty (THA) (Judd et al., 2014; Rasch et al., 2010). A previous study reported the recovery gait and stair climbing function at just 1 year after THA (Heiberg et al., 2013; Judd et al., 2014). However, the functional ability to climb stairs is known to take much longer to return than that of gait (Perron et al., 2003). Additionally, a follow-up investigation performed for 5 years showed that the ability to climb stairs could become limited again over long periods of time (Heiberg and Figved, 2016). Patients with THA exhibit characteristic reductions in stair climbing speed (Stansfield and Nicol, 2002), peak extension support moment, and lower peak hip power in the operated limb (Lamontagne et al., 2011; Queen et al., 2015). While climbing stairs, the vertical ground reaction force (vGRF) acts as a bimodal wave and determines the ability of weight acceptance in the vertical direction (Riener et al., 2002). While climbing stairs, the upper and lower step forces act to simultaneously lift the body upward (Protopapadaki et al., 2007). The peak unilateral vGRF is an important parameter for weight acceptance; however, this parameter does not affect the smooth transfer of ipsilateral loading to the contralateral side. To permit the smooth transfer of ipsilateral loading to the contralateral side, the relationship between force parameters, such as peak vGRF, and temporal parameters, including time to peak force, also must be considered. The first peak vGRF relates to gait speed, which also reflects gait function; therefore, the assessment of first peak force is critical. However, first peak force was reported to be reduced in patients with THA and time to first peak force was prolonged (McCrory et al., 2001). Therefore, to judge gait function, it is necessary to consider the relationship between first peak force and time to first peak force. However, the relationship between climbing time and GRF has not been reported previously; therefore, which GRF parameter causes effects on stair climbing is unknown.

The vGRF is affected by muscle strength; therefore, muscle strength deficit in the operated limb results in reduced GRF in the operated limb and compensation in the non-operated limb. Therefore, it is important to identify the GRF parameter that best represents the climbing time and to clarify the relationship between this parameter and muscle strength; this will allow us to design effective physical therapy strategies to help improve the ability to climb stairs.

This study aimed to investigate differences between climbing time over time and the relationship between climbing time and vGRF. Furthermore, we investigated side-to-side differences in muscle strength and vGRF and the relationship between muscle strength and vGRF. We hypothesized that first peak force and time to first peak force are important for climbing time and that these parameters are associated with the strength of the knee extensors.

Section snippets

Patients

Initially, 52 women were screened for inclusion in this study; however, 18 patients could not participate in tests at 6 months and 12 months and could not climb stairs without a handrail. These 18 patients were excluded from the study. We also excluded patients with any other lower extremity disorders, neurological disorders, or current hip pain. Our final analysis involved 34 females who underwent THA for hip osteoarthritis. Mean (standard deviation [SD]) age, height, and weight were 62.2

Muscle strength at different time points

At 6 and 12 months, the muscle strength of knee extensors in the operated limb was significantly lower than that in the non-operated limb (P ≤ .01; Table 1); however, the muscle strength of the hip abductors and extensors was not significantly lower than that in the non-operated limb (P ≥ .05; Table 1).

Climbing time and vGRF variables at different time points

Patients could climb stairs significantly faster at 12 months than they could at 6 months [6 months, 4.90 (0.6 s); 12 months, 4.32 (0.5 s); P ≤ .001]. Time to Fz1 in the operated limb was

Discussion

The primary purpose of our study was to investigate differences between the time required to climb stairs, climbing time, and vGRF variables. We found that climbing time improved with the time course and that Fz1 increased during the time course, as described previously (Heiberg et al., 2013; Queen et al., 2015). It was previously reported that Fz1 increased as climbing time increased (Riener et al., 2002); however, climbing time was significantly associated with Fz1 in the non-operated limb at

Conclusions

Our data showed that it is important for patients with THA to transfer their weight to the upper steps quickly during climbing. We also revealed that patients with THA depend on muscle strength in the hip extensors, which are stronger than other muscles at 6 months, when they transfer their weight to the next steps. Conversely, we noted that patients with THA transferred their weight to the upper steps without depending on hip function; instead, they used the muscle strength in the knee

Declaration of Competing Interests

There are no conflicts of interest to declare.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Acknowledgements

We would like to thank Editage (www.editage.jp) for English language editing.

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