The aim of this paper was to outline a multilevel modeling approach to fit individual angle-specific torque curves describing concentric knee extension and flexion isokinetic muscular actions in Master athletes. The potential of the analytical approach to examine between individual differences across the angle-specific torque curves was illustrated including between-individuals variation due to gender differences at a higher level. Torques in concentric muscular actions of knee extension and knee extension at 60°·s-1 were considered within a range of motion between 5°and 85° (only torques “truly” isokinetic). Multilevel time series models with autoregressive covariance structures with standard multilevel models were superior fits compared with standard multilevel models for repeated measures to fit anglespecific torque curves. Third and fourth order polynomial models were the best fits to describe angle-specific torque curves of isokinetic knee flexion and extension concentric actions, respectively. The fixed exponents allow interpretations for initial acceleration, the angle at peak torque and the decrement of torque after peak torque. Also, the multilevel models were flexible to illustrate the influence of gender differences on the shape of torque throughout the range of motion and in the shape of the curves. The presented multilevel regression models may afford a general framework to examine angle-specific moment curves by isokinetic dynamometry, and add to the understanding mechanisms of strength development, particularly the force-length relationship, both related to performance and injury prevention.
Introduction The purpose of the study was to assess the occurrence of deficits in strength and power of lower limb muscles and functional performance of patients with back pain syndromes and to identify the factors that affect them. Material and methods The clinical material consisted of 43 patients (28 women with back pain syndrome, the control group - 15 people). Up & go test, Barthel Index, five - time standing up test, Tinetti test, assessment of power (Pmax), strength and optimal shortening velocity (Vopt), Geriatric Depression Scale (GDS), pain assessment were performed in all patients. Results The patients from the control group achieved better results in the five - time standing - up test (p = 0,006), in the Tinetti test (p = 0,04) and had higher knee extensors muscle strength (p = 0,005). Functional performance in patients with lumbosacral spine pain syndromes was determined by the strength of the knee extensors muscles (Up & go test Rho = 0,54; p = 0,005; five - time standing up test Rho = 0,39; p = 0,04; Tinetti for gait Rho = 0,4; p = 0,04). Age and height influenced the parameters of muscle function. Conclusions Patients with back pain syndromes are characterized by reduced functional performance and have knee extensors muscle deficit in relation to people without back pain. Knee extensors muscle strength has the greatest impact on functional performance in patients with back pain. Younger and taller people have better results in muscle function tests.
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