Prevention of sick leave of self-employed farmers should focus on life style (obesity, smoking), reducing older farmers' exposure to physical load, exposure to long-term tractor driving. Specific attention should be paid to animal and mushroom farmers.

The results make it easier to identify groups of farmers to be targeted to prevent sick leave. To reduce the occurrence of sick leave in agriculture, the strategy should be to prevent musculo-skeletal injuries and disorders. Furthermore, a sector-specific approach is recommended, so that preventive actions can be focused on working conditions-specifically on workload and work safety. Efforts to shorten the duration of sick leave will also be valuable to obtain a reduction of sick leave.

The present study was designed to investigate the relationship between muscle performance and electromyogram (EMG) parameters of the trunk extensor muscles in the development of fatigue. Nine subjects performed continuous isometric trunk extensions at 25% and 40% maximal voluntary contraction. The EMG signals of the longissimus thoracis, iliocostalis lumborum, multifidus and latissimus dorsi muscles were recorded. The EMG amplitude (RA-EMG) appeared to increase consistently during the contractions in all muscles, whereas the mean power frequency (MPF) showed a fairly consistent decrease during the contractions. The time constants of the exponential change of the RA-EMG and of the MPF were related to the endurance time. The prediction of endurance based on both EMG parameters appeared to yield better results than the prediction based on the relative force. In particular the time constants of the MPF changes of the multifidus and longissimus muscles appeared to be good predictors of endurance time. The consistency of the spectrum shift of EMG appeared to coincide with a reduced variability of the activation of the muscle involved.

The aim of the present study was to evaluate the viability of a relationship between the temporal activation pattern of parts of the erector spinae muscle and endurance. Seven subjects performed intermittent isometric contractions [4s at 70% maximal voluntary contraction (MVC), 2 s rest] until exhaustion, during which the electromyographical (EMG) activity of the multifidus, iliocostalis thoracis and longissimus muscle segments was recorded. Endurance was defined as the time until exhaustion. Subjects were divided into a high and a low endurance group. The high endurance group showed significantly more variability of EMG amplitude over succeeding contractions. This group demonstrated significantly more alternations of EMG activity between parts of the muscle also. Variability of the EMG amplitude within the contractions did not differ between the groups, nor did MVC. The results indicated that alternating activity between different parts of the erector spinae muscle may function to postpone exhaustion of this muscle as a whole.

Changes in the vasomotion waveform were studied in transverse arterioles (TAs) and their first-order side branches (FOSs) in the tenuissimus muscle of 14 young, anesthetized rabbits during stepwise arterial pressure reduction and local application of adenosine using intravital video microscopy. Pressure reduction resulted in a systematic increase in vasomotion cycle length (CL) and amplitude (A) concomitant with an increase in effective vascular diameter (Deff) and maximum diameter and a decrease in blood flow (Q). During adenosine application Deff and maximum diameter also increased, but CL and A did not change systematically. At moderate pressure reductions and during adenosine application CL changes were limited (less than 1.5 s) and nonsystematic, agreeing with an earlier study (D. W. Slaaf, G. J. Tangelder, H. C. Teirlinck, and R. S. Reneman. Microvasc. Res. 33: 71–80, 1987). In TAs these changes resulted from changes in both the dilation and the constriction phase. In FOSs, however, changes in CL were caused by prolongation of the dilation phase alone. At greatly reduced pressure levels, the CL increase was more pronounced and in both TAs and FOSs was caused by plateau formation in the dilation phase. Stretch of the arteriolar wall does not seem to play a role in control of the vasomotion waveform. Because the onsets of dilation always occur synchronously in TAs and FOSs, but the onsets of constriction do not, vasomotion seems to be a series of rhythmic dilations.