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Department of Geriatric Medicine, Geriatric Day Hospital, Alexandra Hospital, Singapore.
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Abstract |
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Methods. In an observational study, 123 predominantly ethnic Chinese participants aged 50 years and older were recruited from a health promotion program. Main outcome measures were bioelectric impedance for body fat composition, peak oxygen consumption (VO2max), gait speed, handgrip strength, and chair rise time.
Results. The mean age of participants was 
years. Those with a higher self-reported walking level had a better VO2max; every 1 minute per day increase in habitual walking increases VO2max by 0.096 (ml/kg)/min (95% confidence interval [CI] 0.027–0.165, 
) and is possibly associated with a faster gait speed; 
(95% CI 0.000–0.005, 
). There is an age-related rise in body fat composition, decline in VO2max, and slower chair rise time. Men had a lower body fat composition, better VO2max, and stronger handgrip.
Conclusions. Habitual walking may impart important health benefits in terms of improvement in physical performance, fitness, and its implications for the prevention of physical disability in older adults. This also reinforces the theory that low- to moderate-intensity activities may improve cardiorespiratory fitness. There is an inevitable physiological age-related decline in physical fitness.
IT has been suggested that aging and frailty are characterized by a multisystem loss of physiologic reserve capacity. The hallmark of this syndrome is "unstable disability," in which inappropriately large changes in disability are caused by minor external stress. The physiologic capacities postulated to be of significance are (a) musculoskeletal capability, including bone strength, joint flexibility, and muscle strength; (b) aerobic capability, which in part reflects cardiopulmonary capacity; (c) cognitive or neurological capability, including maintenance of balance; and (d) nutritional capacity (1).
Various clinical measures have been used as surrogates of physiologic reserve capacities. These include physical performance and fitness outcomes of bioelectric impedance for body fat composition, peak oxygen consumption (VO2max) for cardiorespiratory fitness, handgrip strength, gait speed, and chair rise time for estimation of musculoskeletal strength, joint flexibility, and balance in older persons. Gait velocity, handgrip strength, and chair rise time have been reported to be important predictors of disability and mobility (2,3).
Increasing physiologic capacity by improving cardiovascular fitness and muscle strength allows older persons to maintain their independence, increase their levels of physical activity, and achieve freedom from disability and falls (4). In addition, regular physical activity and fitness have also been shown to be beneficial in reducing morbidity and mortality secondary to cardiovascular disease, diabetes mellitus, hypertension, and obesity. Others benefits include improvements in bone density, quality of life, and prevention of sarcopenia (5,6).
It is important to make a distinction between physical activity and exercise. Regular or habitual physical activity can be defined as any movement of the body, produced by skeletal muscle contractions, that causes energy expenditure. Exercise, a subset of physical activity, entails a planned, structured, repetitive movement done specifically for maintaining or improving physical fitness. Most data on the effects and benefits of physical activity on fitness were derived from endurance exercise training done on younger persons. However, these works have produced an advice that is usually complex and prescriptive, thus setting a seemingly difficult goal for most sedentary older adults.
There is growing interest on the health benefits and role of low- to moderate-intensity habitual activity (e.g., walking or house or yard work) in the maintenance of physical performance and fitness of older persons (7).
Few studies have assessed whether habitual physical activity, as opposed to exercise and structured training, affects physical performance and fitness in older persons. Studies on physical activity that have mainly used a single sampled activity, such as leisure-time physical activity with VO2max, found that they may not be significantly related (8,9). Others have found that involvement in a structured walking program or exercise training had some association with increased cardiorespiratory fitness (10,11).
However, little is known about the relationship between habitual physical activity and physical performance and fitness in older people. It has been postulated that habitual activity may be more beneficial in the longer term through the engendering of improved fitness or greater physiological activity and energy turnover, especially in older adults. This is also important, as many older adults do not engage in regular exercise programs or leisure-time or sports activities. Results from the Third National Health and Nutrition examination survey (NHANES III) reported that prevalence of little or no leisure-time physical activity among older Americans (aged 50 years and older) ranged from 56% to 58% in men and 64% to 74% in women. Leisure-time physical activity was defined as any type of physically active hobbies, sports, or exercises (12).
Therefore, we investigated the role of regular participation in habitual activities of lower intensity, such as walking, gardening, and house or yard work, compared with leisure-time or sport activities, and their associations with an older person's physical fitness and performance measures after we adjusted for potential confounders (age, gender, health status, and social factors). This is important, because it would have implications in the prevention of disability and morbidity in older persons in a rapidly aging population.
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Methods |
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; 
). This study was approved by the hospital ethics committee.
Questionnaire Assessment
The questionnaire is a one-stage, retrospective, recall-based series of structured questions administered face to face by trained interviewers. Levels of habitual physical activity were assessed by using a detailed activity inventory, modeled after the Nottingham Longitudinal Study of Activity and Aging used and validated by Morgan and associates in 1985 for older adults. Habitual activities are defined as those with a probable minimum energy cost of 2 kcal per minute, performed continuously for a minimum of 3 minutes, at least weekly, for the previous 6 weeks (13). The activities were divided into 5 categories: outdoor productive activities (gardening, house, and car maintenance, and others); indoor productive activities (housework, home maintenance, decorating, and others); walking (any purposeful walking outside house or garden, excluding running or jogging); shopping; leisure-time or sports activities (swimming, running or jogging, racquet games, tai chi or qigong, golf, bowling, dancing, and others). These were recorded if the activities met the criteria for being habitual. The duration and frequency of each reported activity was scored as minutes per day and the number of days per week. They were later scored in average minutes per day.
The extent of walking the day before (walking yesterday), a previously validated question for estimation of walking activity against a pedometer, was done (14). If the previous day had been atypical, then another was selected (up to a maximum of 6 days previously). It was scored as minutes per typical day.
Outcome Variables
Gait velocity was measured while subjects walked over 25 meters on a flat tiled surface. Subjects were instructed to walk as comfortably and quickly as possible on the basis of a standing start. An electronic stopwatch was used to measure the time taken to walk the distance.
Handgrip strength was measured on a Jamar Dynamometer (Sammons Preston, Bolingbrook, IL) on the dominant hand. Subjects were seated and the dynamometer was adjusted until the proximal interphalangeal joints were flexed to 90° with the elbow flexed. Three trials per subject were performed with a 1-minute rest between contractions. The maximal force was recorded as kilogram force (kgf) with a precision of 0.1 kgf.
Chair rise time was performed on a straight-backed chair, with a height from base to seat of 45 cm, with subjects' arms crossed against their chests. The subjects were instructed to sit and rise for 10 cycles as quickly as possible, and the time was recorded with an electronic stopwatch. If subjects were unable to rise without the use of their hands, they were allowed to repeat the process with the use of their hands. If they were unable to complete 10 cycles, the attempted number of cycles was recorded. All participants completed 10 cycles of chair rise time without the use of their hands.
Peak oxygen consumption (VO2max) was calculated by use of the 1-mile Rockport Walk Test: 
, where weight is in pounds, time is expressed in minutes, heart rate is in beats per minutes, age is in years, and gender is 
and 
(15).
Bioelectric impedance for body fat composition was measured by using an Omron Body Fat Monitor HBF-302 (Omron Corp., Tokyo, Japan) with extended outstretched arms. Body weight was measured when the subjects were without shoes and dresses in light clothing; a calibrated electronic scale with a precision of 0.5 kg was used. Height was measured, to the nearest 1 cm, on a flat surface when the subjects were without shoes in an upright position.
Basic demographic, health status, and socioeconomic data (Table 1) included were gender, age, educational level, smoking status, self-rated health, history of hospitalization in the past year, and number of medical problems as possible confounders. The number of medical problems score from 0 (no health problems) to 13, covering the presence or absence of medical comorbidities listed in Table 2 as adapted from Fried and Guralnik's list of chronic disease states that have been associated with physical disability in older populations (16). Self-rated health was rated in a 5-point response format of very poor, poor, fair, good, and excellent.
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The use of a questionnaire introduced an element of self-reporting bias. The question on walking yesterday that was previously validated against a pedometer is highly correlated with reported walking in the past fortnight in this study (Pearson's coefficient 0.737; 
). This lends some reliability to self-reported walking (14) and other self-reported measures of physical activity. The participants were not told about the purpose of the study and were not compensated for their participation, so as to reduce possible bias in the performance testing or the completion of the questionnaire.
The intratest and intertest reliability using the Jamar Dynamometer was previously reported for handgrip strength with good consistency and is recommended for use in clinical practice (17).
Statistical Analysis
We used multivariate linear regression modeling to predict the effect of each component of habitual physical activity (walking, shopping, and indoor and outdoor activities) and leisure-time or sports activities on the physical performance and fitness outcomes of bioelectrical impedance for fat, gait velocity, handgrip strength, and chair rise time. Age, gender, educational level, smoking status, number of medical problems (nominal), history of hospitalization in the past year, self-rated health, and body mass index were entered as covariates together with components of habitual physical activity. All covariates in the model were checked for multicollinearity with good tolerances for individual variables. All analyses were done on the SPSS for Windows Version 10.0 (SPSS, Inc., Chicago, IL). Each component of habitual physical activity and leisure-time or sports activities was scored as average minutes per day. Self-rated health was recategorized into two groups of (a) very poor, poor, or fair and (b) good or excellent. Differences were statistically significant if 
.
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Results |
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). Self-reported leisure-time or sports activities is not significantly associated with VO2max; 
(ml/kg)/min (95% CI -0.029–0.049, 
).
There is a possible correlation between walking with a faster gait speed, although at , the association is just out of statistical significance. Every 1-minute increase in habitual walking correlates with an increase in gait speed of 0.002 m/s (95% CI 0.000–0.005, ) but leisure-time or sports activities are not significant and negatively correlated, at 
m/s (95% CI -0.003–0.000, 
).
None of the habitual physical activities is correlated significantly with better chair rise time. However, those subjects with higher walking and leisure-time or sports activities performed better with less time used for this measure, at 
seconds (95% CI -0.011–0.002, 
) and 
seconds (95% CI -0.007–0.001, 
). Self-reported walking had a similar nonsignificant positive correlation with grip strength (
, 
).
Men performed better in grip strength, at 
kgf (95% CI 7.00–13.78, 
), had a higher VO2max, 
(ml/kg)/min (95% CI 6.26–12.78, ), and were less fat, 
(95% 
, ) than women.
In this group, increasing age was correlated with a higher bioelectric impedance, 
(95% CI 0.039–0.207, 
), a longer chair rise time, 
seconds (95% CI 0.003–0.035, 
) and a lower VO2max, 
(ml/kg)/min (95% 
, ). Age was not significantly correlated with gait speed and grip strength.
Walking as a habitual activity had a median duration of 13.6 min/d (Range 150 min/d) and a mean of 
, and in leisure-time or sports activities with a median duration of 8.6 min/d (range 231 min/d) and a mean of 
(Table 3). Of the subjects, 94.2% reported walking as a habitual activity whereas 62.5% had participation in leisure-time or sports activities. Tai chi (15.8%) was the most popular leisure-time or sports activity, followed by swimming (14.2%) and dancing (13.3%) (Figure 1).
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Discussion |
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In this study, a higher level of habitual walking is significantly correlated with a better cardiorespiratory fitness (VO2max) and possibly a faster gait speed in older persons. This result suggests that older persons with higher involvement in habitual walking compared with leisure-time or sports activities have a better cardiorespiratory function and possibly gait speed.
Benefits of walking have been postulated to be due to two possible modes of action, distinguished by (a) chronic, cumulative adaptations over weeks or months from habitual walking, which may not achieve the desired maximal heart rate for training, and (b) acute, shorter-term effects of walking exercises or training (18). However, cardiorespiratory fitness is itself an important factor for maintenance of activity. Hence, the question on direction of causality has yet to be truly ascertained. Walking should still be encouraged, as it is one of the most accessible ways of being physically active. Benefits of walking may not be limited to the contribution of brisk walking in the improvement or maintenance of physical fitness and performance alone.
At a U.S. National Heart, Lung and Blood Institute workshop on assessment of physical activity and fitness in 1986 (19), self-reported walking was classified to be of low to moderate intensity (1.0–4.9 MET). This reinforces that even modest activity levels may accord health benefits. The added bonus is that modest activities are more likely to be continued, compared with higher-intensity activities such as sports, especially among older persons.
In this study, physical performance and fitness measures were not correlated with leisure-time or sports activities or with any of the other components of habitual physical activity, including shopping and indoor or outdoor activities. This lack of correlation with leisure-time or sports activities may not be surprising. Westerterp and Meijer postulated that involvement in exercise, sports, or leisure-time activities may not prevent an overall decline in physical activity in older persons because of compensation by a decrease in nontraining or habitual activity, in contrast to a younger age group (20). Hence, total physical activity or accumulated energy expenditure may remain the same or even lower than those with mainly habitual activities.
Age is correlated with deterioration in physical performance and fitness in terms of fat impedance, VO2max, and chair rise time. Studies of master athletes have shown that there is a physiological age-related decline in body composition with a reduction in lean muscle mass, muscle strength, and cardiorespiratory function in both men and women (21). It is, however, interesting that there is no significant difference in grip strength and gait speed in this study. This may be a result of the participants, who are self-selected and are likely to represent an elite group of healthy, ambulant, community-dwelling older persons. Gender differences are also expected in terms of body fat composition, grip strength, and VO2max.
McMurdo emphasized that it is unfortunate that public health advice has failed to shake off the high-tech lycra-clad image of aerobic exercise and physical fitness. He suggested that this advice should embrace the broader concept of health and physical activity, which includes low- to moderate-intensity activity such as walking and housework (22). This may allay any preconceived societal notion about aging and physical activity, which may promote inactivity, inability, and disuse in older persons. Poor physical fitness has been shown to be associated with disability and frailty. The question, Can regular physical activity prevent or reverse functional limitations and disability in older adults?, is of great public health importance. We adopted the Nagi model for disablement, which measures the disabling process at distinct levels. This includes measurements of physiologic impairment (VO2max, grip strength) made at organ or organ systems levels and measurements of functional limitations, including the ability to walk (gait speed) and to do a sequence of movements (chair rise time) (23).
In the Nagi model, physical inactivity causes physiologic impairments, which in turn cause functional limitations. Habitual walking may impart important health benefits in terms of better physical fitness and performance. This is indicative of a better physiologic or functional reserve, a term Pandergast used to describe the ability of an individual to adapt to progressive physiologic degeneration (23). An increase in habitual walking may act by causing a positive shift that could enable an older person to function with a higher physiologic reserve to withstand various stress or degenerative factors, including aging (Figure 2).
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Westertap reported that the most important determinant of disability and mortality would be physical inactivity (24). Habitual walking may play a role in the prevention of disability by maintaining and/or improving daily physical function and functional reserve, and increasing level of activity.
In the report "Life in the 21st Century—A Vision for All," the World Health Organization highlighted that, in the next 25 years, the population aged 65 and older is likely to grow by 88% worldwide. Challenges facing an aging nation include how best to postpone disease and disability and to maintain health, independence, and mobility in older individuals (25). In Singapore, the number of older persons above the age of 65 years, who formed 6.8% of the population in 1995, is projected to increase to 20% by the year 2030 (26). As a greater proportion of the population survives to very old ages, health impact in terms of the burden of disability and chronic diseases with related utilization of medical care and need for supportive and long-term care is becoming an important concern.
Further research is necessary to elucidate effects of low- to moderate-intensity habitual walking and physical activity on physical fitness, performance, and its implications on prevention of physical disability in older adults. In an aging population, the ability of the older person to function independently in the community is a critically important public health issue (27).
This study is limited by the small number of participants, and they were more likely to be self-selected, healthy, and interested in physical activity. They were also predominantly ethnic Chinese. It is, however, heartening to find that low to moderate levels of physical activity like habitual walking also afford benefits in physical performance and fitness and its possible role in the prevention of physical disability. The benefits of walking, in terms of physical fitness and performance, may not only be limited by how fast one does it (brisk walking) but also be altered by whether an older person does it habitually.
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Acknowledgments |
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We are grateful to all participants, physiotherapists, and occupational therapists involved in this program. We also thank Y. H. Chan and L. Shen, biostatisticians, for their invaluable advice on statistical analysis.
Address correspondence to Dr. Chek Hooi Wong, Department of Geriatric Medicine, Geriatric Day Hospital, Alexandra Hospital, 378 Alexandra Road, Singapore 159964. E-mail: Chek_Hooi_WONG{at}alexhosp.com.sg
Received June 3, 2002
Accepted October 29, 2002
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