Do you have a client who’s having trouble fitting exercise into her daily routine? Does she claim she doesn’t have enough time to work out continuously for 30 minutes or more at a time? According to
a study published in the February 2006 issue of the National Strength & Conditioning Association’s Journal of Strength and Conditioning Research (2006; 20 [1], 130–35), your client may not be able to cite time constraints as an excuse anymore.

A group of 37 low to moderately active individuals, aged 29–65, were split into an “intermittent” exercise group and a “continuous” exercise group. The following health-related variables were tested for each participant: blood lipids, walking economy, blood pressure, maximal oxygen consumption and body composition. Measurements were taken at baseline, after 12 weeks and at the end of the 24-week study.

Both groups performed cardiovascular exercise four times per week. Researchers steadily increased intensity from 50%–60% of heart rate reserve (HRR) during the first few weeks to 70%–80% of HRR from week 5 to week 24. The continuous group exercised for 30 minutes, while the intermittent group split their exercise into two 15-minute bouts. After 12 weeks, the intermittent group showed improvements in walking economy and high-density lipoprotein cholesterol levels; decreases in diastolic and systolic blood pressure; and a 4.2% increase in VO2max over the continuous group. The continuous group experienced only a decrease in diastolic blood pressure. Body composition remained consistent in both sets.

Groups traded programs for the remaining 12 weeks, according to study authors, “to act as their own controls and provide baseline, 12-week and 24-week dependent variable data.” After 24 weeks, the original intermittent group showed an increase of 4.1% VO2max over the continuous group. This, according to authors, was evidence that previously acquired improvements in health and fitness evidence had been successfully maintained.

Though both groups experienced improvements, study authors concluded that the twice-a-day group’s achievements were greater than the once-a-day group’s when intensity was increased incrementally. “We would suggest that for those individuals beginning an incremental exercise program . . . intermittent activity patterns could be recommended, and if exercise intensity is increased periodically, benefits similar to the results of the present study will be observed,” authors stated.