Introduction

Fall-related injuries, including head injuries and fractures, are serious problems in the elderly, as they often lead to prolonged or even permanent disability. Thus, prevention of falls and therefore of the injuries associated with them would reduce disability, improve the quality of life, and reduce the costs of health care. Impairment of muscle strength and muscle power of the lower extremities, balance/postural control, and walking ability has been recognized as important risk factors for falls [1]. These parameters are known to become progressively more impaired with aging [2], suggesting the increased risk for falls in the elderly.

Muscle strength should be distinguished from muscle power; muscle strength is defined as the maximal force that a muscle can produce against a give resistance, while muscle power is defined as the product of force and speed [1, 3]. The former is related to bone strength, whereas the latter is related to falling [1, 3–5]. Thus, improvement of muscle power rather than muscle strength would appear to be important in the prevention of falls in the elderly.

Exercise is generally accepted to be effective for the prevention of falls in the elderly. A meta-analysis study has demonstrated that exercise is effective for lowering the risk of falls in the elderly and that the consequent reduction in the incidence of fall-related injuries reduces health care costs [6]. Furthermore, a systematic review has demonstrated that muscle strengthening, balance exercises, and regular practice of the internal martial art therapy of tai chi chuan are effective for preventing fractures in the elderly [7–9]. Theoretically, however, improvement of muscle power of the lower extremities, balance/postural control, and walking ability by exercise is considered to be important in the prevention of falls in the elderly. In particular, Runge et al. [1] reported that whole-body vibration exercise improved chair-rising time in terms of muscle power in the elderly. With the exception of this study, however, less attention would appear to have been paid to muscle power in the literature as far as the prevention of falls is concerned. The present study was conducted to determine the effect of exercise on the prevention of falls in the elderly, aimed at improving flexibility, body balance, muscle power, and walking ability.

Methods

Sixty-eight elderly ambulatory volunteers (seven men and 61 women) who visited the Department of Orthopaedic Surgery of two hospitals and three Orthopaedic Clinics in Suginami, Nakano, and Setagaya Wards, Tokyo, Japan between July 2006 and March 2007 were recruited to our trial. The inclusion criteria were an age of more than 50 years, fully ambulatory, and being able to measure parameters as described below, and the exclusion criteria were severe gait disturbance with some aids, severe round back due to osteoporotic vertebral fractures, acute phase of diseases, and severe cardiovascular disease. The mean age of the participants was 76.4 years (range, 66–88 years). The physical activity level at baseline was considered comparatively low in all of the participants because none of them had been laborers or had been engaged in any regular or leisure time sporting activities.

We assessed the ratio of male to female subjects, age, body weight, height, body mass index, history of falls in the past 3 months and fractures after 50 years of age, and the indices of flexibility (finger floor distance [FFD] with the body flexed in the anterior, right, and left directions), body balance (tandem standing time, tandem gait step number, and unipedal standing time), muscle power (timed up and go [TUG] [10] and chair-rising time [five times]), and walking ability (10-m walking time and walking step length). Tandem standing time and unipedal standing time were determined by taking the mean values of the right and left sides.

The subjects were randomly divided into two groups: the exercise and control groups (n = 34 in each group). Main diseases that could possibly affect physical activity in the participants were osteoporosis with or without radiographic vertebral fractures (n = 13), sciatica due to lumbar spinal canal stenosis (n = 8), knee osteoarthritis (n = 7), and spondylosis (n = 6) in the exercise group, and osteoporosis with or without radiographic vertebral fractures (n = 11), sciatica due to lumbar spinal canal stenosis (n = 8), spondylosis (n = 8), knee osteoarthritis (n = 5), hip osteoarthritis (n = 1), and elbow arthritis (n = 1). All of the degenerative diseases were mild to moderate. Thus, the healthiness and subsequent medication of the participants were similar at baseline in the two groups. The daily exercise program (Table 1) consisted of calisthenics, body balance training (tandem standing, tandem gait, and unipedal standing), muscle power training (chair-rising training), and walking ability training (stepping). All of the exercises were supervised and performed in the clinics or hospitals 3 days/week only in the exercise group by taking about 30 min. So, the compliance with the exercises was 100%. No exercise was undertaken in the control group. The period of this study was 5 months. The incidence of fall and fracture as well as the above-mentioned indices of the flexibility, body balance, muscle power, and walking ability was assessed 2.5 and 5 months after the start of the trial. In particular, information regarding falls and fractures was obtained every week by directly asking the participants.

Table 1 Daily exercise program in the exercise group
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Informed consent was obtained from each of the subjects prior to their participation in the study. The protocol was approved by the Ethical Committee of Keiyu Orthopaedic Hospital.

An intention-to-treat (ITT) analysis was adopted. Data are expressed as means ± standard deviation in tables and means ±95% confidence intervals (CIs) in figures. The use of 95% CIs facilitates the distinction between statistical significance and clinical significance or practical importance in figures. The Mann–Whitney U test was used to compare baseline characteristics between the two groups. A one-way analysis of variance (ANOVA) with repeated measurements was used to analyze the longitudinal changes in physical function parameters within a group. An analysis of covariance (ANCOVA) was used to compare changes in physical function parameters at each time point between the two groups using baseline values as covariates. The chi-square test was used to compare the baseline characteristics such as the ratio of male to female subjects and the incidence of falls and fractures between the two groups. All statistical analyses were performed using the Stat View J-5.0 program (SAS Institute, Cary, NC, USA). The significance level was set at P < 0.05 for all the comparisons.

Results

Number of subjects who were included in the ITT analysis

All participants in the exercise group completed the 5-month trial. However, one participant in the control group dropped out from the trial because of noncompliance at 5 months after the start of the trial. Thus, 34 subjects in the exercise group were included in the ITT analysis at the baseline and 2.5 and 5 months after the start of the trial, whereas 34 subjects in the control group were included in the ITT analysis at the baseline and 2.5 months after the start of the trial, dropping to 33 subjects at 5 months after the start of the trial.

Anthropometry and baseline physical function of the study subjects

Tables 2 and 3 show the anthropometry and baseline physical function of the study subjects, respectively. The mean age was significantly different between the two groups (74.6 years in the exercise group and 78.2 years in the control group, P < 0.01). However, there were no significant differences in any other baseline characteristics including the ratio of male to female subjects, body weight, height, body mass index, and percentage of subjects who had experienced falls in the past 3 months and fractures after 50 years of age. There were ten fallers (29.4%) in the exercise group at baseline: five had experienced only one fall, and five had experienced two falls. There were also ten fallers (29.4%) in the control group at baseline: four had experienced only one fall, five had experienced two falls, and one had experienced four falls. There was a history of 14 clinical fractures in 11 participants (32.4%) of the exercise group: eight vertebral fractures, three hand fractures, two rib fractures, and one forearm fracture. There also was a history of 12 clinical fractures in eight participants (23.5%) of the control group: six vertebral fractures, two forearm fractures, two foot fractures, one rib fracture, and one ankle fracture. There were no significant difference in any of baseline physical function indices of flexibility (FFD), body balance (unipedal standing time, tandem gait step number, tandem standing time), muscle power (TUG, chair-rising time), and walking ability (10-m walking time, step length) between the two groups.

Table 2 Anthropometry of the study subjects
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Table 3 Physical function of the study subjects—flexibility, body balance, muscle power, and walking ability indices
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Effect of exercise on the indices of flexibility, body balance, muscle power, and walking ability

Figures 1, 2, 3, and 4 show the effect of exercise on the indices of flexibility (FFD), body balance (unipedal standing time, tandem gait step number, tandem standing time), muscle power (TUG, chair-rising time), and walking ability (10-m walking time, step length), respectively. The one-way ANOVA with repeated measurements showed that all indices of flexibility, body balance, muscle power, and walking ability significantly improved in the exercise group, whereas FFD in the right and left directions significantly worsened in the control group. The ANCOVA showed that, after the 5-month intervention, there were significant differences in FFD in the right and left directions, unipedal standing time, tandem gait step number, tandem standing time, TUG, chair-rising time, 10-m walking time, and step length between the exercise and control groups. However, FFD in the anterior direction did not differ significantly between the two groups.

Fig. 1
figure 1

Finger floor distance with anterior, right, and left flexion of the body. Data are expressed as means ±95% confidence intervals. The one-way analysis of variance with repeated measurements showed that FFD in the anterior direction significantly improved in the exercise group (P < 0.01) but not in the control group and that FFD in the right and left directions significantly improved in the exercise group (both P < 0.05) but significantly worsened in the control group (both P < 0.05). The analysis of covariance showed that, after the 5-month intervention, there were significant differences in FFD in the right and left directions between the exercise and control groups. However, FFD in the anterior direction did not differ significantly between the two groups. NS not significant, asterisks significant changes by the one-way ANOVA with repeated measurements

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Fig. 2
figure 2

Unipedal standing time, tandem gait step number, and tandem standing time. Data are expressed as means ±95% confidence intervals. The one-way analysis of variance with repeated measurements showed that unipedal standing time, tandem gait step number, and tandem standing time significantly improved in the exercise group (all P < 0.0001) but not in the control group. The analysis of covariance showed that, after the 5-month intervention, there were significant differences in unipedal standing time, tandem gait step number, and tandem standing time between the exercise and control groups. NS not significant, asterisks significant changes by the one-way ANOVA with repeated measurements

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Fig. 3
figure 3

Timed up and go and chair-rising time. Data are expressed as means ±95% confidence intervals. The one-way analysis of variance with repeated measurements showed that TUG and chair-rising time significantly improved in the exercise group (both P < 0.0001) but not in the control group. The analysis of covariance showed that, after the 5-month intervention, there were significant differences in TUG and chair-rising time between the exercise and control groups. NS not significant, asterisks significant changes by the one-way ANOVA with repeated measurements

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Fig. 4
figure 4

Ten-meter walking time and step length. Data are expressed as means ±95% confidence intervals. The one-way analysis of variance with repeated measurements showed that 10-m walking time and step length significantly improved in the exercise group but not in the control group (P < 0.01 and P < 0.05, respectively). The analysis of covariance showed that, after the 5-month intervention, there were significant differences in 10-m walking time and step length between the exercise and control groups. NS not significant, asterisks significant changes by the one-way ANOVA with repeated measurements

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Effect of exercise on the incidence of falls and fractures

Four participants in the control group experienced one fall each during the 5 months intervention period. Of four falls, one was due to a stumble of the toe, and three were caused by lurches. There was no multiple faller during the 5 months intervention period. In particular, a participant of the control group who had experienced four falls in the past 3 months at baseline (multiple faller) had no fall during the 5 months intervention period. The incidence of falls during the study period was significantly lower in the exercise group than in the control group (0.0% vs. 12.1%, χ 2 = 4.383, P = 0.0363). Above four falls resulted in bruises or sprains of the upper extremities, which required no intensive treatment and healed within several days. There were no fall-related fractures reported in either group.

Adverse events

During the study period, no serious adverse events, such as severe fall-related injuries or adverse cardiovascular effects, were observed.

Discussion

The muscle power of the lower extremities, balance/postural control, and walking ability are important factors in the prevention of falls in the elderly. The focus of the present study was (1) whether the exercise program (three times per week, aimed at improving flexibility, body balance, muscle power, and walking ability) would improve those related parameters in the elderly; and (2) whether improvement of these parameters, if any, would be useful to prevent falls. Thus, a randomized controlled trial was designed. We confirmed that our exercise program improved flexibility, body balance, muscle power, and waling ability, leading to a reduced incidence of falls.

A consensus has been reached with respect to exercise programs for the elderly; that is, a combination of muscle-strengthening exercises of the back and lower extremities, balance exercises, and walking may be effective to prevent vertebral and nonvertebral fractures [11]. Theoretically, however, improvement of muscle power of the lower extremities, balance/postural control, and walking ability are all important to prevent falls in the elderly. Although muscle strength, which is related to bone strength, has often been assessed in the literature, less attention has been paid to muscle power despite the fact that it is related to falling. In the present study, we therefore included the indices, not of muscle strength, but rather of muscle power such as the chair-rising time and TUG.

However, we did not apply brisk walking exercises to improve walking speed because there are controversial reports on the effect of walking exercise on the incidence of falls. Feskanich et al. [12] showed in a cohort study that, among postmenopausal women, walking for at least 4 h/week was associated with a 41% lower risk of hip fracture compared with less than 1 h/week. On the other hand, Gillespie et al. [7] showed in a systematic review that brisk walking increased the risk of upper limb fractures in elderly women. Based on the hierarchy of the evidence, we believe more in the result of the systematic review. Therefore, we applied only stepping, which might be safe from the point of view that exercise therapy should be safe. However, 10-m walking time and TUG were significantly improved in the exercise group compared with the control group, suggesting the usefulness of stepping in the forward, back, right, and left directions in improving walking speed in the elderly.

Exercise also increased the walking step length. Basically, each stride during walking consists of the stance and swing phases. Thus, increased unipedal standing time can produce more stable walking. That is, the more the stance phase of each leg was stabilized by exercise, the greater the swing of the other leg becomes, resulting in an increase in step length. Because impaired walking ability is associated with decreased walking step length [13], increased walking step length may also indicate improved walking ability. Because it is important for the elderly to increase walking step length to touch the ground with the heel during walking in order to prevent falls caused by toe-contact-related stumbling, we believe that improvement of walking step length could also lead to a reduction in the fall-related risk.

We applied exercise 3 days/week. The intensity and frequency of the exercise program were considered to be reasonable for the elderly (mean age, 76.4 years) to be continued without any fatigue and difficulty for 5 months. Exercise was not only effective to prevent falls but also was well tolerated, and no serious adverse events, such as fall-related injuries or adverse cardiovascular effects, were observed in any of the subjects during the exercise program, suggesting the safety of our exercise program.

Flexibility in terms of FFD in the right and left directions was impaired during the 5-month period in the control group (only 3–4 cm increases in the FFD). The reason for this remains uncertain because there was nobody with a significant collapse in his/her status or who had a significant change in medication. However, this result possibly suggests that not only muscle strength and muscle power of the lower extremities, balance/postural control, and walking ability [2] but also flexibility could be impaired with aging. So, an exercise regimen aimed at improving flexibility should be included in the exercise therapy.

There is a criticism that the subjects of the control group were older and tended to be frailer than those of the exercise group despite the similar proportion of fallers in the two groups and less history of clinical fractures in the control group at baseline. Lacking in statistically significant differences in physical function parameters at baseline between the two groups might not be due to similarity of the parameters but be attributable to a large variation of the parameters. In order to resolve this issue, ANCOVA was used to compare changes in physical function parameters at each time point between the two groups using baseline values as covariates.

There were strengths in this study. First, this randomized controlled trial was strictly performed not by exercise-related experts but mainly by general practitioners so that our exercise program could be performed by general practitioners without using any special machines. Second, exercises aimed at improving flexibility, body balance, muscle power, and walking ability improved the parameters related to these functions, leading to a reduction in the incidence of falls as a primary end point. Third, the exercise program was safe and well tolerated in the elderly. These strengths suggest the usefulness and convenience of our exercise program in the prevention of falls in the elderly.

The limitations of this study should also be discussed. First, the study period was short (5 months). It is a recognized fact that long-term exercise is needed to reduce the life-time risk of falls and fall-related injuries in the elderly. However, because our exercise program proved easy for our elderly subjects to continue without any difficulty, we believe that it could be continued under the instruction of general practitioners. Second, the number of the study subjects was small, even though the statistically significant results were obtained. Thus, further studies are needed to resolve the limitations.

In conclusion, the present study showed the beneficial effect of an exercise program aimed at improving flexibility, body balance, muscle power, and walking ability to prevent falls in the elderly. Our exercise program improved flexibility (FFD with the body flexed in the right and left directions), body balance (tandem standing time, tandem gait step number, and unipedal standing time), muscle power (TUG and chair-rising time), and walking ability (10-m walking time and step length), leading to a reduced incidence of falls, and the beneficial effect of our exercise program in preventing falls in the elderly was thus confirmed. Furthermore, the exercise program was safe and well tolerated by all our subjects.