Forty-nine previously sedentary or low active individuals aged 40 to 71 years were allocated to three groups. The long walking group participated in an 18-week walking programme which consisted of walks lasting 20 to 40 min; the repetitive short walking group completed walks of between 10 and 15 min, up to three times a day, with no less than 120 min between each walk; and the control group maintained their low level of activity. Both walking programmes began at a prescribed 60 min/week, which increased steadily up to 200 min/week by week 12. During the study, the long walking group walked for an estimated 2514 min (139 min/week), expending an estimated 67.5 MJ (3.72 MJ/week) at an estimated 73% of their age-predicted maximum heart rate and 68% of their estimated VO2max. The repetitive short walking group walked for an estimated 2476 min (135 min/week), expending an estimated 58.5 MJ (3.17 MJ/week) at an estimated 71% of their age-predicted maximum heart rate and 65% of their estimated VO2max. The results showed a statistically significant reduction in heart rate during a standardized step test (pre- versus post-intervention) in both walking groups, indicating an improvement in aerobic fitness, although the control group showed a higher average heart rate during the post-intervention test, indicating reduced fitness. When compared with the male subjects pre-intervention, the females possessed more favourable levels of high-density lipoprotein (HDL) cholesterol (p < 0.001), apolipoprotein (apo) AI (p < 0.001) and ratios of total cholesterol:HDL cholesterol (p < 0.02) and low-density lipoprotein (LDL) cholesterol: HDL cholesterol (p < 0.02). Compared with the controls post-intervention, the walking groups showed no statistically significant changes in total cholesterol, LDL cholesterol, HDL cholesterol, apo AI, apo AII, apo B, or the ratios of total cholesterol: HDL cholesterol, LDL cholesterol: HDL cholesterol, apo AI: apo B or apo AI: apo AII (p > 0.05). Relative to the walking groups, factor XIIa increased in the control group (p < 0.05). We conclude that, although both walking programmes appeared to improve aerobic fitness, there was no evidence of improvements in the blood lipids or associated apolipoproteins of the walking groups. Further analysis indicated that this apparent lack of change may have been related to the subjects' relatively good pre-intervention blood lipid profiles, which restricted the potential for change. The implications of the observed changes in the coagulation/fibrinolytic factors remain unclear.

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