Elsevier

Clinical Biomechanics

Volume 40, December 2016, Pages 14-19
Clinical Biomechanics

Lecture
Efficacy of a progressive resistance exercise program to increase toe flexor strength in older people

https://doi.org/10.1016/j.clinbiomech.2016.10.005Get rights and content

Highlights

  • We compared a progressive strengthening program to a simple home-based foot exercise program.

  • Adherence to supervised, group exercise classes focussed on the feet was very high.

  • 12 week progressive resistance training increases toe strength in older people.

  • General foot exercises (e.g. picking up marbles) do not increase toe strength.

  • Foot exercises improve balance in older people.

Abstract

Background

Reduced toe flexor strength is an independent predictor of falls in older people. However it is unknown whether strengthening programs can restore toe flexor strength in older individuals. The aim of this study was to investigate whether a progressive resistance training program, focused specifically on the foot muscles, could improve toe flexor strength in community-dwelling older people.

Methods

After baseline testing, 85 men and women (age range 60–90 years) were randomized to either a supervised, progressive resistance training (n = 43) or a home-based exercise (n = 42) group for 12 weeks. A further 32 participants were recruited for a control group. The primary outcome measures were hallux and lesser toe flexor strength pre- and post-intervention. Secondary outcome measures were exercise compliance, components of the Foot Health Status Questionnaire and single-leg balance time.

Findings

Average class attendance was 89% with 68 participants from the two intervention groups (80%) completing the follow-up assessments. Participants in the supervised, progressive resistance training group significantly increased their toe strength (up to 36%; P < 0.02), whereas there was no change in toe strength in either the home-based or control groups. This increased toe strength was accompanied by a significant improvement in perceived general foot health and single-leg balance time compared to the other groups (P < 0.05).

Interpretation

Progressive resistance exercises are a viable intervention to increase toe flexor strength in older adults. A clinical trial is now required to determine whether this intervention can reduce the number of falls suffered by older adults.

Introduction

A decline in muscle strength is typically regarded as an inevitable consequence of ageing, and age-related loss of muscle mass is one of the main determinants of frailty. Muscle atrophy in older adults has been associated with an annual decline in lower leg strength of approximately 3% (Goodpaster et al., 2006). This muscle atrophy and strength loss can arise from muscle disuse and are inversely associated with changes in physical activity (Kent-Braun et al., 2000). Although under researched compared to other lower limb muscles, it appears that muscles within the feet also suffer from atrophy and an associated loss of strength with ageing. For example, older adults have 27–36% less toe flexor muscle strength than their younger counterparts (Endo et al., 2002, Menz et al., 2006). This reduction in toe flexor strength is likely to have a profound effect on the ability of older adults to walk safely. An individual's toes are in contact with the ground for 75% of the stance phase when walking(Hughes et al., 1990) and the long toe flexor muscles help control forward progression of the leg over the foot (Hamel et al., 2001). This could be critical when attempting to take corrective steps to maintain balance in a near-fall situation. Of concern, a prospective study of over 300 older people found that fallers had a reduction of > 20% in their hallux and lesser toe strength compared to non-fallers (Mickle et al., 2009). Hallux strength was also found to be a stronger predictor of falls than other more commonly measured falls risk factors, such as age, gender, falls risk score and quadriceps strength. In fact, each unit (% body weight) increase in hallux strength decreased the odds of sustaining a fall by 7% (Mickle et al., 2009).

Strengthening the toe flexor muscles should improve the ability of the toes to perform their specific roles in balance and walking. Supporting this theory, Kokkonen et al. (1988) monitored athletes while they completed toe resistance training for 12 weeks. Compared to an age- and gender-matched control group, toe flexor strength increased by approximately 46% and resulted in a significant improvement in vertical jump performance. Similarly, Unger & Wooden (2000) employed a within-subject design whereby 15 men and women (aged 21–62 years) completed toe strengthening exercises (Archxerciser™) on one foot over 6 weeks. Compared to the “untrained” (control) foot, toe flexor strength improved almost four-fold after 6 weeks. Importantly, these unilateral strength gains were accompanied by significant improvements in single limb horizontal and vertical jump performance. The most impressive toe strength gains have been reported in 14 males who performed high resistance toe training, which resulted in a 60–70% increase in toe flexor strength (Goldmann et al., 2013). These results suggest that increasing toe strength can lead to improved motor task performance in young adults.

There is emerging evidence that toe-strengthening exercises may be effective for older adults or people with foot pathologies. For example, individuals with pes planus (flat feet) exhibited significant increases in hallux flexor strength following a 2-month intervention program that incorporated the Short Foot strengthening exercise (Jung et al., 2011). Other research has associated toe exercises with improved motor task performance in older adults. Nine nursing home residents undertook training three times a week using their toes to gather a weighted towel and pass beanbags from one place to another (Kobayashi et al., 1999). After 8 weeks the toe-grasp training was found to significantly improve the participants' spontaneous sway performance with both their eyes open and closed by 16% and 26%, respectively. In contrast, no change, or poorer balance was displayed by an age-matched control group, who participated in a group exercise program. Unfortunately, although balance performance improved after toe-grasp training, toe strength was not measured in this study. Therefore, it is unknown whether the training lead to toe strength gains or whether improvements in balance were associated with some other mechanism. Toe strengthening exercises were also included in a multifaceted podiatry intervention study involving older adults with foot pain and who were identified as being at an increased risk of falling (Spink et al., 2011). This intervention (foot orthoses, advice on footwear, footwear subsidy, a home-based program of foot and ankle exercises, a falls prevention education and routine podiatry care) resulted in a 36% reduction in falls incidence compared to the control group who received routine podiatry care for 12 months. The toe-strengthening portion of the program consisted of participants completing exercises on an Archxerciser™ and picking up stones with their toes, three times a week for 6 months. At the 12 month conclusion of the intervention, a non-significant 9% increase in toe flexion strength was reported. This program, however, was non-progressive (resistance did not increase as strength improved) and did not target the intrinsic foot muscles (Spink et al., 2011). Consequently, the objective of the current study was to address the limitations in previous studies, by investigating whether a progressive resistance training program, focused specifically on the foot muscles, could improve toe flexor strength in community-dwelling older people. We hypothesized that older people who participated in the structured 12-week progressive resistance training program would increase their toe flexor strength more than older people who performed home-based general foot exercises and controls.

Section snippets

Design overview

This study was a longitudinal study with parallel and randomized allocation of two exercise interventions to determine the effectiveness and adherence of each program. A control group, who were unavailable to participate in the exercise program due to other commitments, was assessed to allow comparison of the outcome variables to the exercise groups. Due to logistics associated with implementing the interventions (i.e. the intervention needed to be completed before a summer holiday break), the

Results

Fig. 1 shows the flow of participants through the study. Participants in the three groups had very similar characteristics at baseline (see Table 2).

Discussion

The aim of this study was to determine whether a progressive resistance training program, focused specifically on the foot muscles, could strengthen the toe flexor muscles in community-dwelling older people in comparison to home-based general foot exercises and controls. The findings indicate that older people can significantly increase both their hallux and lesser toe flexor strength by participating in a structured, progressive group exercise class within a 12-week program. The implications

Funding

This work was supported by the Illawarra Health and Medical Research Institute and completed while Dr. Mickle held an Australian National Health and Medical Research Council Post-doctoral Fellowship (Overseas Clinical Training Fellowship, ID 1016521). The funding agencies did not have a role in the design, conduct, or reporting of the study or in the decision to submit the article for publication.

Acknowledgements

The authors wish to acknowledge all of the participants in the trial. The authors would like to thank the Clinical Trials Unit staff at the Illawarra Health and Medical Research Institute for assistance with the group exercise classes.

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Permanent address: Institute of Sport Exercise and Active Living, Victoria University, Melbourne, VIC 8001, Australia.

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