CARDIAC DEMANDS OF HEAVY SNOW SHOVELING

Objective.-To assess the physiologic responses to manual (shoveling) vs automated (electric snow thrower) snow removal in healthy, untrained men. Design.-Observational, controlled trial. Setting.-A community-based, acute care, teaching-research hospital. Participants.-A volunteer sample of 10 apparently healthy untrained men (mean+/-SD age = 32.4+/-2.1 years) met all eligibility criteria and completed the study. Intervention.-Each subject cleared two 10+/-2-cm-high, 15-m-long tracts of heavy, wet snow in the cold (2 degrees C), using self-paced manual and automated methods, in random order, with 10- to 15-minute rest periods between each 10-minute bout of work. Main Outcome Measures.-Heart rate, blood pressure, oxygen uptake, and perceived exertion during snow removal were compared with values obtained during maximal arm-ergometer and treadmill tests. Results.-Mean heart rate during shoveling was 154 and 173 beats per minute at 2 and 10 minutes, respectively, corresponding to 86% and 97% of maximal heart rate. Relative heart rate (percentage of maximal heart rate) during shoveling was inversely related to aerobic fitness (r= -0.65; P=.05). The highest heart rate and perceived exertion responses during shoveling, arm-ergometer, and treadmill testing were comparable. Systolic blood pressure during snow shoveling (198+/-17 mm Hg) was significantly greater (P<.003) than during arm ergometry or automated snow removal and slightly greater than during maximal treadmill testing (181+/-25 mm Hg). Oxygen uptake during shoveling was similar to that for arm ergometry (5.7 vs 6.3 metabolic equivalents), but lower than for treadmill testing (9.3 metabolic equivalents). Cardiorespiratory and perceived exertion responses were reduced during automated snow removal. Conclusion.-Heavy snow shoveling elicits myocardial and aerobic demands that rival maximal treadmill and arm-ergometer testing in sedentary men. These responses may contribute to cardiovascular events reported after heavy snowfalls.