Strength asymmetry of the knee extensors and physical activity in middle-aged women

Background: Differences between muscle strength and power of lower limbs is one of the factors associated with falls in the elderly population. Muscle strength asymmetry of lower limbs increases with age. Objective: The aim of the study is to assess differences in the volume and intensity of physical activity (PA) in the subgroups of women being at higher and lower risk of falls (with and without strength asymmetry of the knee extensors of dominant and non-dominant lower limb). Methods: Data from 42 women (age 56.3 +/- 4.4 years; weight 76.5 +/- 16.1 kg; body height 164.3 +/- 5.2 cm; body mass index 28.1 +/- 5.3 kg.m(-2)) were used for the purpose of the presented analysis. Furthermore the sample was divided into subgroups with lower and higher strength asymmetry of quadriceps muscle (as a criterion the asymmetry greater than 15% was chosen). Absolute concentric peak torque of the knee extensors was evaluated by an isokinetic dynamometer IsoMed 2000 in a sitting position at angular velocity of 180 degrees.s(-1). PA was monitored using Yamax SW-700 pedometers throughout 7 consecutive days and using the Czech version of standardized International Physical Activity Questionnaire. Results: Statistically significant differences between groups with lower and higher strength asymmetry were found in the amount of self-reported vigorous PA (p = .04; d = 0.6) only. Differences between the observed groups were not significant in self-reported moderate PA and walking. There were also no significant differences in the daily numbers of steps measured objectively. Conclusions: The results of the study indicate that from the point of view of strength asymmetry of knee extensors as a factor associated with falls in middle-aged women, intensity of PA could be an important characteristic of PA. This suggestion should be taken into account in habitual PA and training programs in middle-aged population.