Brisk walking is one of the recommended forms of exercise for older adults to achieve physiological benefit (NHS Scotland, 2001). Although the proportion of those reporting their walking speed as ‘brisk’ declines with increasing age (Skelton et al. 1999), it is not clear whether old age alters the response to this walking speed descriptor. The purpose of the study was to test this hypothesis.

The Lothian Research Ethics Committee approved the study. Healthy elderly (75Ð83 years, n = 9) and healthy young (20Ð23 years, n = 9) female volunteers walked 150 m around an indoor 50 m circuit, in response to standardised walking speed instructions which required the subject to complete two separate walks at each of a ‘slow’, ‘comfortable’, ‘brisk’, and ‘fast’ pace. Each of the eight walks was timed and absolute (m s^-1) and relative (% maximum) walking speeds were calculated. Maximal walking speed was measured separately over 10 m, from a walking start. Absolute oxygen cost (ml kg^-1 min^-1) was measured by an ambulatory system (Metamax 3B, Cortex Biophysik). Relative oxygen cost (%×_O2,max) was calculated from ×_O2,max measured during progressive treadmill walking on two separate occasions (mean ×_O2,max: young volunteers, 38.55 ± 2.19 ml kg^-1 min^-1; elderly volunteers, 20.40 ± 4.37 ml kg^-1 min^-1; means ± S.D.). A test was defined as maximum upon the investigators’ subjective assessment that the individual could not continue, plus a respiratory exchange ratio of ²ge³1.10 (young volunteers) or ²ge³ 1.00 (elderly volunteers). The responses to ‘brisk’ walking are reported below. Data were analysed using Student’s unpaired t tests.

The elderly volunteers walked at a significantly slower mean absolute walking speed (1.37 m s^-1 (S.D. = 0.156) elderly, 1.68 m s^-1 (0.11) young; P < 0.001, Fig. 1A) but at a similar proportion of maximal walking speed (70.48% (8.04) elderly, 66.29% (6.76) young; P = 0.248, Fig.1B). Although the mean absolute ×_O2 was significantly lower in the elderly group (13.6 ml kg^-1 min^-1 (2.94) elderly, 17.48 ml kg^-1 min^-1 (2.41) young; P = 0.008, Fig. 1C), %×_O2,max was significantly higher (67.15% (20.58) elderly, 45.05% (4.48) young; P = 0.026 (n = 7 elderly, n = 6 young), Fig. 1D).

The elderly group walked at a similar (mean) proportion of maximal speed (70 %) when compared with the young group (66 %), but at a higher (mean) relative cost (67 % ×_O2,max elderly, 45 % ×_O2,max young). This ‘cost’ difference should be acknowledged when choosing walking speed instructions for training and rehabilitation programmes for elderly people.

We are indebted to our volunteers for their co-operation and enthusiasm.

All procedures accord with current local guidelines and the Declaration of Helsinki.