Effects of a workplace physical exercise intervention on the intensity of headache and neck and shoulder symptoms and upper extremity muscular strength of office workers: a cluster randomized controlled cross-over trial.

The purpose of the study was to examine the effects of a workplace physical exercise intervention on the perceived intensity of headache and the intensity of symptoms in the neck and shoulders, as well as on the extension and flexion strength of the upper extremities. The study was a cluster randomized controlled trial. The cross-over design consisted of physical exercise intervention (15 weeks) and no-intervention (15 weeks). The subjects (n=53) were office workers (mean age 46.6 (SD 8.4)) who reported headache (n=41) symptoms in the neck (n=37) or shoulders (n=41), which had restricted their daily activities during the last 12 months. Pain symptoms were measured using the Borg CR10 scale and muscular strength with a 5RM test. Statistical analyses were based on linear mixed models. Physical exercise intervention resulted in a slight, but statistically significant, decrease in the intensity of headache and neck symptoms, as well as an increase in the extension strength of the upper extremities. The mean decrease in headache during the 5-week period was 0.64 CR10 (95% CI 0.28-1.00) (P=0.001) or 49% (95% CI 22-77), and 0.42 CR10 (95% CI 0.11-0.72) (P=0.002) or 49% (95% CI 13-85) in the intensity of neck symptoms. The mean increase in the extension strength of the upper extremities was 1.3 kg (95% CI 0.5-2.1) (P=0.001) or 4% (95% CI 1-6). The intervention had no effect on the intensity of shoulder symptoms or the flexion strength of the upper extremities. Specific exercise may be clinically important to alleviate headache and neck symptoms.

The effects of mating system and genetic variability on susceptibility to trematode parasites in a freshwater snail, Lymnaea stagnalis.

The amount and distribution of genetic variability in host populations can have significant effects on the outcome of host-parasite interactions. We studied the effect of mating system and genetic variability on susceptibility of Lymnaea stagnalis snails to trematode parasites. Mating system of snails from eight populations differing in the amount of genetic variability was manipulated, and self- and cross-fertilized offspring were exposed to naturally occurring trematode parasites in a controlled lake experiment. Susceptibility of snails varied between populations, but mating-system treatment did not have a significant effect. Heterozygosity of snails was negatively correlated with the probability of trematode infection, however, suggesting that parasitic diseases may pose a serious threat to populations lacking genetic variability.

The effect of inbreeding rate on fitness, inbreeding depression and heterosis over a range of inbreeding coefficients.

Understanding the effects of inbreeding and genetic drift within populations and hybridization between genetically differentiated populations is important for many basic and applied questions in ecology and evolutionary biology. The magnitudes and even the directions of these effects can be influenced by various factors, especially by the current and historical population size (i.e. inbreeding rate). Using Drosophila littoralis as a model species, we studied the effect of inbreeding rate over a range of inbreeding levels on (i) mean fitness of a population (relative to that of an outbred control population), (ii) within-population inbreeding depression (reduction in fitness of offspring from inbred versus random mating within a population) and (iii) heterosis (increase in fitness of offspring from interpopulation versus within-population random mating). Inbreeding rate was manipulated by using three population sizes (2, 10 and 40), and fitness was measured as offspring survival and fecundity. Fast inbreeding (smaller effective population size) resulted in greater reduction in population mean fitness than slow inbreeding, when populations were compared over similar inbreeding coefficients. Correspondingly, populations with faster inbreeding expressed more heterosis upon interpopulation hybridization. Inbreeding depression within the populations did not have a clear relationship with either the rate or the level of inbreeding.