Joint knee loads during squat with constant or variable resistance in males. A clinical trial.

BACKGROUND: In the squat movement, the use of constant resistance (CR) generates greater compression and shear forces close to 90° of knee flexion, increasing joint overload. However, when used variable resistance (VR) there is no consensus about the effect of knee joint load. The aim of this study was to compare knee torques using constant or variable resistance during the squat exercise. METHODS: Twenty-one healthy male subjects (mean age, 24 [SD, 3] years; height, 1.76 [SD, 0.04] m), who practice squats during strength training routine. Were simultaneously record data from the platform force and tridimensional kinematic to obtain torques around knee. 15 repetitions were performed up to maximum knee flexion with the use of variable (RV) or constant (CR) resistance in a single session. RESULTS: Significant differences regarding the angles only in the sagittal plane at the end of the ascending phase of the squat, with less knee extension in the VR condition. In the sagittal and frontal planes, lower values of extensor and abductor torque were found in the VR condition at the angles of greater knee flexion. CONCLUSION: The use of variable resistance compared to constant resistance seems to be an alternative to be considered when the objective is to minimize the internal loads on the knee joint in exercises such as the squat in amplitudes of greater flexion. This study indicated that VR helps subjects who are learning the squat movement, enabling the application of this knowledge in physical therapy or physical training clinics.

Effects of a noncircular chainring system on muscle activation during cycling.

Previous studies evaluated cycling with noncircular chainrings and suggested that changes in muscle activation would occur in response to altered pedaling mechanics throughout the crank arm revolution. However, no previous study addressed this question. The aim of this study was to compare the magnitude of muscular activity between a conventional and a noncircular crank system during an incremental maximal cycling test. Seven mountain-bike trained cyclists completed two incremental maximal tests, separated by 48 h, one for each crank system. Each test started with a workload of 100 W and was increased by 30 W every minute until exhaustion. Power output, pedaling cadence and heart rate were monitored and compared between the crank systems using paired t-tests. Surface EMG was recorded from the right rectus femoris, vastus medialis, biceps femoris and gastrocnemius medialis. EMG was compared using a general linear model considering as factors the crank system and workload with post hoc analysis at α=0.05. RMS presented effect of workload, but no effect of crank system was found for the muscles analyzed. The present results do not support effects of the noncircular crank system on variables of performance and muscle activation during incremental cycling in trained mountain bike cyclists.

Effects of workload on seat pressure while cycling with two different saddles.

INTRODUCTION: Seat pressure during cycling and its relationship to urological disorders have been discussed extensively in recently published literature. The effects of exercise configuration on seat pressure, however, still have not been fully investigated. AIM: This study evaluates the effects of two different pedaling workloads and two saddle designs on saddle pressure in 22 (11 men and 11 women) recreational cyclists (bicycling <2 hours per week). METHODS: Seat pressure was measured in the saddle surface while pedaling at workloads of 150 and 300 W using a plain and a holed saddle model, both without any gel cushion characteristics. Analysis of variance was applied to compare seat pressure between situations. MAIN OUTCOME MEASURE: Study the importance of bicycle saddle pressure. RESULTS: Mean seat pressure was not different between men and women. For the plain saddle, the men's average seat pressure increased as the workload increased. Using a holed saddle, the mean pressure increased as the workload increased, regardless of gender. CONCLUSIONS: The increase of workload increased the seat pressure for the subjects, with the main effects dependent on workload. The use of a holed saddle was not directly related to lesser seat pressure during cycling. Our results support our understanding of a similarity between genders related to mean seat pressure, and suggest that different workload ranges may present different results for seat pressure.

Bicycle saddle pressure: effects of trunk position and saddle design on healthy subjects.

OBJECTIVE: There is a common belief that seat pressure during cycling can compress specific neurovascular tissues over the perineum leading to genital pathologies. This topic has seldom been discussed for women. The present study was conducted to verify the effect of trunk position and saddle design on saddle pressure in both men and women. METHODS: Recreational cyclists (11 men and 11 women) were evaluated while seated on a bicycle. Saddle pressure was measured with F-scan insoles adapted for two saddle models (with and without a hole), and two trunk positions (upright and forwards). Pressure values were compared between trunk positions and saddles employing ANOVA. RESULTS: There were no statistical differences comparing saddle pressure between the two trunk positions for women. For men a statistical difference between the trunk positions for the saddle with a hole was found. Thus, the trunk forwards shift seems to affect the values of saddle pressure only for men using the 'holed' saddle. CONCLUSION: Saddle pressure for men was influenced by saddle design and trunk position only. This result indicates that the masculine anatomy may influence saddle pressure during bicycle.

Avaliação do posicionamento corporal no ciclismo competitivo e recreacional / Evaluation of body position of competitive and recreational cyclists

O objetivo desse estudo foi avaliar e comparar o posicionamento na bicicleta adotado por ciclistas de diferentes níveis. Os ciclistas avaliados foram classificados como competitivos (atletas) e recreacionais (não-atletas). Um total de 36 ciclistas entre recreacionais (n=17) e competitivos (n=19) foram avaliados, cada qual na sua própria bicicleta. Para asavaliações foi utilizado um protocolo proposto pela literatura. Os dados foram submetidos à estatística descritiva, indicando ocorrência de desajustes no posicionamento em 82% dos ciclistas recreacionais e em 74% dos ciclistas competitivos avaliados. Para os ajustes no selim foram encontrados os erros mais comuns, relacionados com a posição vertical e horizontaldo selim (observados para 82% dos ciclistas recreacionais e 79% dos ciclistas competitivos). O segundo erro com um grande número de observações foi a altura do guidom (observados em 12% dos ciclistas recreacionais e 5% dos ciclistas competitivos). Com base nestes resultados, percebe-se que os ciclistas recreacionais estão mais suscetíveis a desajustes no posicionamento do que ciclistas competitivos, o que pode acarretar lesões no futuro. Os erros no posicionamento encontrados podem estar relacionados ao tempo de prática de cada grupo.

The purpose of this study was to evaluate and to compare the body position when cycling of cyclists of different levels. The subjects were classifi ed as athletes (competitive) or non-athletes (recreational). A total of 36 recreational (n=17)competitive (n=19) cyclists were evaluated in their own bicycles. The body position assessment was carried out using a protocol that is well-recognized in the literature. The results demonstrated misalignment in the body positioning of 82% of the recreational cyclists evaluated, and 74% of the competitive cyclists evaluated. Saddle maladjustments were found tobe the most common misalignments, related to both horizontal and vertical positioning of the saddle (observed in 82% of recreational cyclists and 79% of the competitive cyclists). Handlebar height was the second most common misaligned bicycle adjustment observed (observed in 12% of the recreational cyclists and 5% of the competitive cyclists). Based on the resultsobtained from the assessment of cyclists' positioning, it was observed that the recreational cyclists are more susceptible to misalignments in body position during cycling; a situation that could indicate injuries in the future. These results can be explained by the different amount of time spent in the addle by the two groups due to their different objectives.