Physical workload, perceived exertion, and output of cut wood as related to age in motor-manual cutting

Physical workload, output of cut wood, and perceived exertion were studied among 15 younger (mean age 29 years) and 16 older (mean age 59 years) lumberjacks, using a chainsaw and paid on a piece-rate basis. Oxygen consumption was measured with portable equipment, while heart rate was measured telemetrically. The oxygen consumption for all working phases was 1.8 +/- 0.2 l/min (means +/- SD) (younger) and 1.5 +/- 0.2 l/min (older), which corresponded to 49 +/- 4% and 53 +/- 7% of maximal oxygen consumption estimated in ergometer bicycle exercise test. A negative relationship was found between relative oxygen consumption at work and maximal oxygen consumption (ml/kg/min). Mean heart rates for all working phases were 138 +/- 10 beats/min (younger) and 126 +/- 17 (older). The heart rate differed between the working phases, and was significantly higher for both groups during bunching than during the other operations. The output of cut wood did not differ significantly between the groups. Slight but significantly relationships were found between output of cut wood and maximal oxygen consumption (ml/kg/min) and oxygen consumption (ml/kg/min) during work. Rating of perceived exertion (RPE) and simultaneous heart rate recordings during cycle tests and field studies showed significant correlations between heart rate and RPE values during cycling in both groups. RPE values and heart rate in the field showed a slight correlation (younger) and not at all (older).