Background: The 2007 American College of Sports Medicine (ACSM) and the American Heart Association (AHA) physical activity guidelines recommend adults engage in either 150 minutes of moderate intensity or 60 minutes of vigorous intensity physical activity per week to derive health benefits.
Purpose: In a 6-month clinical trial, we examined whether walking programs of moderate (leisurely-paced) and vigorous (fast-paced) intensity produced improvements in cardiorespiratory fitness as predicted by the ACSM/AHA guidelines.
Methods: Participants (N = 155) were instructed to walk 30 minutes per day on 5 or more days per week, at either a moderate or vigorous intensity level (45–55% or 65–75% of maximum heart rate reserve [HRres ], respectively). Within each condition, we categorized participants based on their mean weekly amounts of exercise as reflected in written self-monitoring logs. Fitness was assessed by a maximal graded exercise test at pre- and post-treatment. This trial was conducted in Gainesville, FL between 1999 and 2003.
Results: Mean minutes of walking were related to changes in cardiorespiratory fitness in the vigorous (r = .47; p = < .001) but not moderate intensity condition (r = .07; p = .52). Within the vigorous intensity condition, significantly greater improvements in fitness were achieved by participants with high and medium amounts of accumulated exercise compared with those with low amounts of exercise.
Conclusions: Clinically meaningful improvements in cardiorespiratory fitness were observed in participants who walked a minimum of 60 minutes per week at a fast-pace but not those who walked at a leisurely-pace. These findings support the 2007 ACSM/AHA physical activity recommendations regarding vigorous, but not moderate, intensity physical activity for cardiorespiratory fitness.