The Women on the Move Through Activity and Nutrition (WOMAN) study, a 5-year randomized clinical trial, was designed to evaluate whether a non-pharmacological lifestyle intervention, focused on weight loss through dietary and physical activity changes, would reduce the measures of subclinical atherosclerosis among postmenopausal women aged 52–62 years. Data were collected at baseline and at month 48. Pettee and colleagues [1] have recently reported data from the WOMAN study assessing changes in leisure-time physical activity (LTPA) and body composition vis-a-vis concomitant changes in 400-m walk time. At baseline, participants (n = 508) were randomized to the lifestyle intervention or health education group. The lifestyle intervention focused on weight (7–10%) and waist circumference reduction through healthy lifestyle behavior change. Change in walk time over 48 months was the primary outcome. Secondary measures included change in LTPA and body composition parameters including body weight, body mass index, waist circumference, and dual-energy X-ray absorptiometry-derived fat and lean mass. 
Increased LTPA and reductions in body weight, body mass index, waist circumference, and fat mass were associated with shorter (faster) walk time at month 48 compared to baseline. LTPA was not significantly related to walk time in the health education group. The authors of this study concluded that increased LTPA and weight loss resulted in improved physical function, as measured by the 400-m walk, in a group of overweight, postmenopausal women and that their findings support the use of the 400-m walk to evaluate progress in physical activity or weight loss programs [1].

Comment
Self-paced walking tests were developed to provide a familiar and acceptable method of estimating cardiorespiratory fitness and exercise tolerance in older adults and in various diseases (congestive heart failure, multiple sclerosis, etc.). There is ample evidence to support the usefulness of the 400-m walk as an estimate of cardiorespiratory fitness, functional status, and general health among older adults, but the current study by Pettee demonstrated its importance also in younger subjects. 

In a 2001 study of older adults, Simonsick and colleagues showed that, when compared with the 6-min walk, participants performed closer to maximal capacity when asked to walk a given distance [2]. Results from previous studies done by the authors examining the 400-m walk in middle-aged women provide promising data [3,4]. Using baseline data from the WOMAN study, longer 400-m walk times were significantly associated with increased clinical and subclinical cardiovascular disease risk [3]. Interestingly, in a 2010 validation study that also included middle-aged women, the 400-m walk time was shown to be highly reproducible over a 1-week interval, a valid estimate of measured VO2max (maximal oxygen uptake), and significantly related to a comprehensive profile of physical activity and fitness measures [4].

We recently corroborated that cardiorespiratory fitness was negatively associated with age, percentage fat mass, visceral fat area, body fat-muscular condition, and central adiposity-muscular condition. Only time elapsed since menopause revealed a statistically significant correlation with VO2max. Age and time of menopause aside, body fat-muscular condition was related to the VO2max variation, presenting an interactive effect with basal metabolic rate. Central adiposity-muscular condition also affects VO2max [5].

The findings from the new study by Pettee and colleagues add relevant data to their previous work assessing the psychometric properties and potential use of the 400-m walk in middle-aged women [4]. In the current study, weight loss and positive change in healthy behavior resulted in improved physical function. These findings clarify the value of the 400-meter walk as a supplemental measure to evaluate progress in non-pharmacological lifestyle interventions or general weight loss programs.

Camil Castelo-Branco
Ob Gyn Senior Consultant, Hospital Clínic Barcelona, and Full Professor, University of Barcelona, Spain

References
1. . Pettee Gabriel KK, Conroy MB, Schmid KK, et al. The impact of weight and fat mass loss and increased physical activity on physical function in overweight, postmenopausal women: results from the Women on the Move Through Activity and Nutrition study. Menopause 2011;18:759-65.
http://www.ncbi.nlm.nih.gov/pubmed/21705864
2. Simonsick EM, Montgomery PS, Newman AB, Bauer DC, Harris T. Measuring fitness in healthy older adults: the Health ABC Long Distance Corridor Walk. J Am Geriatr Soc 2001;49:1544-8.
http://www.ncbi.nlm.nih.gov/pubmed/11890597
3. Pettee KK, Larouere BM, Kriska AM, et al. Associations among walking performance, physical activity, and subclinical cardiovascular disease. Prev Cardiol 2007;10:134-40.
http://www.ncbi.nlm.nih.gov/pubmed/17617776
4. Pettee Gabriel KK, Rankin RL, Lee CD, Charlton ME, Swan PD, Ainsworth BE. Test-retest reliability and validity of the 400 meter walk test in healthy, middle-aged women. J Phys Act Health 2010;7:649-57.
http://www.ncbi.nlm.nih.gov/pubmed/20864761
5. Aragao F, Abrantes C, Gabriel RE, et al. Effects of body composition and menopause characteristics on maximal oxygen uptake of postmenopausal women. Menopause 2011 July 11. Epub ahead of print.
http://www.ncbi.nlm.nih.gov/pubmed/21712735