The relevance of figure-of-eight walk test to hip muscle strength in healthy young males

Abstract

[Purpose] This study aimed to investigate the contribution of hip muscle torque to figure-of-eight walk (F8W) test in healthy young males. [Participants and Methods] Twenty healthy young males (40 limbs; mean age, 21.7 ± 0.6 years) participated. We measured the maximum F8W speed and steps. The hip muscle strengths (MS) of the flexor, extensor, abductor, and adductor muscles as well as the internal and external rotators (ER) were measured using a handheld belt-stabilized dynamometer. The hip muscle torque to weight-bearing index (WBI) is expressed as the measured MS divided by the lower thigh or shin length and body weight. [Results] F8W-time and F8W-rate were relevant to the ER-WBI (F8W time: β=−0.330; F8W rate: β=0.369). [Conclusion] This study’s findings suggest that hip ER strength contributes to F8W in healthy young males.

INTRODUCTION

Many real-world movements involve walking and turning to adapt to daily living environments¹⁾. Turning can cause the body’s center of gravity to deviate from the horizontal plane, which can lead to instability and falls²⁾. Previous studies have reported older adults takes slower turns when compared to younger adults³⁾, which is associated with a higher risk of falls⁴⁾, and resultant hip fractures⁵⁾. The Figure-of-eight Walk Test (F8W) test was designed to assess an individual’s ability to turn while walking during activities of daily living⁶⁾. The reliability and validity of the F8W has been verified as a gait skill assessment tool in the elderly⁶⁾, as well as in patients with stroke⁷⁾, multiple sclerosis⁸⁾, Parkinson’s disease⁹⁾, and amputation¹⁰⁾. Turning while walking is a complex movement that requires both motor and sensory functions²⁾. Therefore, identifying turn-related motor functions is important for safety in the living environment.

Turnings have thus far been clinically evaluated and kinematically analyzed^{11, 12)}. Kinematic analyses have shown that the turning strategy includes both spin and step turns^{11, 12)}, and the asymmetric motion of the left and right lower extremities indicates the difference in hip joint motion¹²⁾ and step length^{13, 14)}. These reports suggest that step length affects turning^{3, 15)}. In addition, turning has been reported to be dependent on the angle of rotation and angular velocity of the head and pelvis¹⁶⁾. Turning occurs in a top-down order, starting with the head, and followed by the trunk, pelvis, and feet. Further, the direction of turning is related to the angle of rotation of the trunk and pelvis, and the turning walking speed is related to the angular velocity of the trunk and pelvis¹⁵⁾. Head movements occur during turns to gather advanced visual information regarding the trajectory and any potential obstacles¹⁷⁾. In contrast, changes in direction while walking are determined by the orientation of the head, trunk, pelvis, and feet, suggesting the involvement of rotational hip movements. In a previous study, change of direction performance in athletes was reported to be related to hip muscle strength¹⁸⁾; however, the specifics of motor functions related to change of direction have not been clarified. Clarification of motor functions related to change of direction may contribute to the acquisition of safe and smooth mobility in real-life spaces. Therefore, we hypothesized that the F8W, an assessment of walking skills, might be relevant to hip muscle strength, and examined in healthy young men in this study. It would be clinically significant to identify motor functions that contribute to turning as a necessary exercise therapy for turning.

PARTICIPANTS AND METHODS

The participants comprised 20 individuals with a total of 40 legs (mean age, 21.7 ± 0.6 years). The participants were 171.7 ± 6.7 cm tall, weighed 68.3 ± 10.8 kg, and had a BMI of 23.1 ± 3.3 kg/m² (Table 1). Participants received a detailed explanation of the study procedure, and all participants provided written informed consent. The study was conducted in accordance with the principles of the Declaration of Helsinki, and was approved by the Institutional Review Board of the International University of Health and Welfare (18-Ifh-009). The exclusion criteria were as follows: the presence of any musculoskeletal, neurological, or cardiopulmonary problems or hip strength insufficient to comply with the instructions of the experiment.

Table 1. Participants characteristics.

	Average ± SD
Age (years)	21.7 ± 0.6
Height (cm)	171.7 ± 6.7
Weight (kg)	68.3 ± 10.8
BMI (kg/m2)	23.1 ± 3.3
Thigh length (cm)	38.7 ± 3.2 / 38.7 ± 3.3
Shin length (cm)	40.6 ± 3.8 / 40.7 ± 3.5

N=20 (40 legs). BMI: body mass index; SD: standard deviation.

In this study, the F8W was used to evaluate the participants’ gait skills (walking and turning abilities)⁶⁾. During the F8W test, the participants stood at the center of a set of two cones spaced at 1.5 m intervals. Participants standing with their feet together in the starting position were subsequently instructed to walk and turn at the two cones for the measurements at maximum speed. The maximum speed was measured twice, and the better of the two results of time was used for analysis. The F8W rate was calculated as the number of measured F8W steps divided by the F8W time (steps/s).

The hip muscle strength was measured using a belt-stabilized handheld dynamometer (μ-Tas F1; Anima Co. Tokyo, Japan). The measurement position for the hip muscle strength was similar to that of the manual hip muscle testing procedure. The muscle strengths of the hip flexor, internal rotation (IR), and external rotation (ER) were measured in the sitting position, with the hip and knee joints flexed at 90°. The hip extensor muscle strength was measured in the prone position, with the knee joint flexed at 90°. Hip abduction and adduction muscle strengths were measured in the supine position. The contact point for the dynamometer was 1 cm proximal to the medial and lateral malleoli in the hip internal and external rotation muscle strength measurements¹⁹⁾, as well as the front, back, lateral, and medial sides of the distal part of the thigh in the hip flexor, extensor, abduction, and adduction muscle strength measurements^20,21,22). The participants were instructed to cross their arms in front of their chest and to push as hard as possible into the dynamometer for 5 s. The hip muscle torques were expressed as the measurement of the muscle strength divided by the body weight and lower limb length (Weight-bearing-index: WBI).

All statistical analyses were performed using SPSS (ver. 28.0; IBM Corp., Armonk, NY, USA). The Pearson correlation coefficient was used to determine the relationship between the hip muscles WBI (flexor, extensor, adductor, abductor, IR, and ER), and F8W-time, F8W-steps and F8W-rate. Linear regression analysis was used to determine the hip muscle WBI relevant to F8W-time, F8W-steps and F8W-rate. The F8W-time, F8W-steps and F8W-rate were the dependent variable. Independent variables included the hip muscles WBI (flexor, extensor, adductor, abductor, IR, and ER). Variables demonstrating p-values <0.20 were included in a linear multiple regression analysis using the stepwise method to determine. The significance level was set to a p<0.05.

RESULTS

Table 1 shows the basic characteristics of the participants. Table 2 shows the results of F8W-time, steps, rate, and hip muscle WBI. F8W-time was correlated to hip adductor (r=−0.312, p=0.050), abductor (r=−0.300, p=0.060), IR (r=−0.285, p=0.075), and ER (r=−0.333, p=0.038) WBI. F8W-rate was correlated to hip abductor (r=−0.287, p=0.072), IR (r=−0.282, p=0.078), and ER (r=−0.369, p=0.019) WBI. A significant linear regression was observed, which indicated that the F8W-time and F8W-rate were relevant to the hip ER-WBI (F8W-time: B=−2.295, 95% CI −4.450 to −0.140, β=−0.330, p=0.038, F8W-rate: B=0.847, 95% CI 0.146 to 1.547, β=0.369, p=0.019) (Table 3).

Table 2. Results of F8W and hip muscle WBI.

	Average ± SD
F8W
Time (sec)	4.1 ± 1.0
Steps (step)	9.6 ± 1.5
Rate (steps/sec)	2.4 ± 0.4
Hip muscle WBI (Nm/kg)	Right / Left
Flexion	1.47 ± 0.50 / 1.55 ± 0.46
Extension	0.86 ± 0.33 / 0.84 ± 0.30
Adduction	0.62 ± 0.25 / 0.60 ± 0.23
Abduction	0.84 ± 0.26 / 0.82 ± 0.31
Internal rotation	0.55 ± 0.18 / 0.51 ± 0.16
External rotation	0.55 ± 0.13 / 0.54 ± 0.17

F8W: figure-of-eight walk test; WBI: weight bearing index; SD: standard deviation.

Table 3. Regression analysis.

Dependent variables	Independent variables	B	95% CI	β	p-value
F8W-time	Hip ER-WBI	−2.295	−4.450; −0.140	−0.330	0.038
F8W-rate	Hip ER-WBI	0.847	0.146; 1.547	0.369	0.019

B: unstandardized coefficients, β: standardized coefficients.

F8W: figure-of-eight walk test; ER: external rotators; WBI: weight bearing index; CI: confidence interval.

DISCUSSION

The results of this study showed that the F8W-time was significantly relevant to hip ER-WBI. The movement pattern of turning has been reported to be velocity independent, with rotations of the head, trunk, pelvis, and lower extremities occurring in that order^15,16,17). It has further been reported that changes in direction are related to the trunk and pelvis rotation angle¹⁵⁾, bilateral lower extremity support, and lateral lower extremity step width¹³⁾, whereas turn speed is related to the rotation speed of the head, trunk, and pelvis, stride length, and rotation angle of the foot^{13, 15, 16)}. These reports suggest that the rotation angle and speed of the trunk and pelvis are important for the turning. Furthermore, in the turn stance phase, the medial and lateral lower-extremity movements were asymmetrically combined. A spin turn with the medial lower extremity involves internal hip rotation and extension after knee extension and external hip rotation¹²⁾. In addition, the lower extremity joint torque during the spin turn showed significantly increased hip extension, internal and external rotation compared with that of the step turn²³⁾. Therefore, we speculate that the relevance of F8W-time to ER-WBI is that in spin turns, the hip internal rotation motion is controlled by the eccentric contraction of the hip external rotator muscles. On the other hand, the change of direction by the step turn is decelerated by the erector spinae, biceps femoris, and soleus muscles, then moved in the direction of rotation by the center of mass with pelvic elevation by the gluteus maximus and ankle joint inversion by the tibialis anterior muscles¹²⁾. Therefore, the external hip rotators may not contribute in the change of direction in the step turn.

In addition, the F8W-rate was significantly associated with hip ER-WBI. Stability during the turn is affected by increased forward instability at the middle of the swing and increased lateral instability at the opposite heel contact in spin and step turn²⁴⁾. Therefore, the strategy may be to minimize the swing phase, which is unstable during the turn, in order to ensure the speed and safety of the turn performed in this study. We speculate that hip external rotation muscle strength contributes to the higher gait rate by inhibiting hip internal rotation motion during the pivot turn.

In conclusion, the results showed that the F8W-time and F8W-rate were relevant to the hip ER-WBI in healthy young males. The present study reveals some of the motor function contributions in the F8W of healthy young males.

A limitation of this study is the use of isometric muscle torque at the hip, which does not reveal muscle function as observed in F8W. Future studies will examine the contribution of hip muscle function in F8W using isokinetic muscle torque.

Conference presentation

The authors shared these findings at the Physical Therapy Science conference September 28, 2019, Okawa, Fukuoka.

Funding and Conflict of interest

This research was supported by the JSPS KAKENHI Grant numbers 22K17636 (SO). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.