Responses of people with coronary artery disease to common lawn-care tasks

Abstract

The primary purpose of the present study was to determine oxygen uptake ($\dot VO_2$) and heart rate (HR) responses of patients with coronary artery disease (CAD) to common lawn-care activities. The study was conducted in three phases. In phase I, 8 men with CAD performed 30 min of push motorized lawn mowing at a self-paced rate. In phase II, 9 men with CAD performed push (no power) mowing, trimming (power and manual), and raking for 8 min each. In phase III, age-matched men and women with and without CAD (9–11 per group) performed self-propelled motorized mowing and push motorized mowing. In phase I,$\dot VO_2$ averaged 17.3 (SEM 3.8) ml · kg⁻¹ · min⁻¹ during 30 min of mowing. Relative effort was 68 (SEM 1) and 76 (SEM 4)% of treadmill maximal$\dot VO_2$ ($\dot VO_{2max}$) and HR, respectively. In phase II, mean$\dot VO_2$ ranged from 8.6 (SEM 0.4) with grass trimming to 22.2 (SEM 1.6) ml · kg⁻¹ · min⁻¹ with push manual mowing. With self-propelled mowing at three speeds in phase III, mean$\dot VO_2$ of the CAD groups ranged from 9.5 (SEM 0.3) to 13.8 (SEM 1.4) ml · kg⁻¹ · min⁻¹ and represented 37%–62%$\dot VO_{2max}$. The results indicated that lawn mowing is often performed at an exercise intensity recommended for aerobic exercise training; patients who achieve a treadmill peak capacity of 4 times resting metabolic rate (4 METs) should be able to perform self-propelled motorized lawn mowing (slow speed) and grass trimming at less than 80% peak$\dot VO_2$; and$\dot VO_2$ demands of lawn mowing can be adjusted by equipment selection and/or pace.