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Objectives This study examined the physiological strain experienced by workers employed in motor-manual timber harvesting performed in winter and summer, and the applicability of heart rate indices for estimating energy expenditure. Material and Methods The heart rates (HR) of 2 teams consisting of 2 persons working simultaneously during felling and forwarding, in both winter and summer, were measured. Heart rate at work (HR work ), resting heart rate (HR rest ), relative heart rate (%HRR), ratio of working heart rate to resting heart rate, and 50% level were used to estimate the physiological workload in particular jobs. The HR index (HR work /HR rest ) equation was used to estimate the energy expenditure (EE). Results For all jobs, significantly higher physiological workload and energy expenditure were recorded during winter. Conclusions The season significantly affects the physiological workload during logging operations. If there is no possibility of harvesting wood in summer, in order to limit the workload of workers during winter activity, attention should be paid to the proper organization of work and selection of workers. Int J Occup Med Environ Health. 2022;35(4):437–47

The purpose of this study was to establish the impact of season on productivity, labour consumption, and working time structure during timber harvesting from young alder stands (Alnus glutinosa Gaertn.). An early thinning process was performed in summer and winter in pure alder stands (38 and 40 years old) in the Płaska Forest Division (NE Poland). The felling and processing operations were performed by experienced loggers using the cut-to-length (CTL) system, and forwarding with manual loading and unloading involved the use of a Zetor 7045 (65 HP) farming tractor and trailer. In both summer and winter, the loggers spent most of their labour time on felling trees (approx. 23%) and bucking (approx. 36%). Assistant loggers spent most of their time stacking logs (49.2% in summer and 58% in winter). The most time-consuming activities in forwarding were loading, unloading, and transportation. The average time consumption of tree felling and processing amounted to 0.36 ± 0.11 h/m3; that of forwarding was lower, at 0.24 ± 0.07 h/m3. No statistically significant differences in the labour consumption of tree felling were identified between winter and summer (p = 0.863). For forwarding, labour consumption was significantly higher in winter (0.28 h/m3) than in summer (0.19 h/m3, p = 0.001). Average productivity was 3.02 ± 1.09 m3/h for tree felling and 4.76 ± 1.80 m3/h for forwarding. The productivity of felling was similar in winter (2.83 m3/h) and in summer (3.22 m3/h). For forwarding, productivity was significantly higher in summer (5.70 m3/h) than in winter (3.81 m3/h, p < 0.01).

The aim of this study was to investigate the effect of season of the year on the frequency and degree of damage to residual trees caused during winter and summer timber harvesting operations in young alder stands. Analyses were conducted in pure black alder (Alnus glutinosa Gaertn.) stands aged 38 and 40 years, located in north-eastern Poland. Chainsaw logging was performed in the cut-to-length (CTL) system, while timber was extracted using an agricultural tractor with a trailer with manual timber loading and unloading. Damage caused in the stand as a result of early thinning operations was evaluated in terms of: (1) damage location, (2) wound size, (3) wound depth, and (4) the distance of the damaged tree from the skid trail. Timber harvesting caused damage in 8.3% of trees remaining in the stand. Both the total number of damaged trees (p = 0.001) and the number of trees damaged during felling (p = 0.01) and extraction of timber (p < 0.001) were greater in summer than in winter. Irrespective of the season, two-thirds of all cases of damage were caused during timber extraction, with 67.7% of damage recorded on trunks or root collars and 32.3% on roots. Irrespective of the season and the technological operation, slightly over 50% of cases of damage were small wounds of max. 10 cm2. The proportions of medium-sized wounds (11−100 cm2) and large wounds (over 100 cm2) were comparable. The majority of damaged trees (85.1%) were found in the vicinity (p < 0.001).