RESUMO

O objetivo deste estudo foi verificar a influência do posicionamento do indivíduo na bicicleta, durante a pedalada, sobre a sobrecarga mecânica na coluna cervical. Foram avaliados nove indivíduos durante teste em uma bicicleta de competição acoplada a um ciclossimulador. O protocolo consistiu em pedalar em quatro posturas (ereta, descanso, intermediária e ataque), com filmagem simultânea no plano sagital. As imagens foram digitalizadas no software DVideow e possibilitaram o cálculo das variáveis cinemáticas, as quais foram inseridas no modelo biomecânico, permitindo o cálculo da força muscular (FM) e da força articular (FA). Os resultados demonstraram que quando os indivíduos modificaram sua postura de ereta para descanso, de descanso para intermediária e de intermediária para ataque, os valores médios e máximos das FM e FA aumentaram (p<0,05). Assim, concluiu-se que as magnitudes das FM e FA aumentam à medida que a coluna cervical se torna mais estendida e anteriorizada.

This study examined the influence of the subject position on the bicycle during pedaling, on the mechanical overload in the cervical spine. Nine subjects were evaluated during the test on a racing bicycle coupled to a cyclesimulator. The protocol consisted in pedaling in four different postures (erect, rest, intermediate and attack), with video filming in the sagittal plane. Images were digitized using the software DVideow, which enabled the calculation of kinematic variables, later inserted into the biomechanics model to calculate the muscle (FM) and joint (FA) forces. When the subjects changed from erect to rest posture, rest to intermediate posture, intermediate to attack posture, the mean and the maximum values of FM and FA have increased (p<0.05). Therefore, there was a significant increase in the FM and FA forces as the cervical spine became more extended and projected forward.

RESUMO

BACKGROUND AND PURPOSE: Pain is currently evaluated with "subjective" methods (eg, patient self-report). This study aimed to test whether fatigue indexes are able to accurately discriminate between subjects with and subjects without low back pain. SUBJECTS: Sixty subjects separated into 2 groups--a group with low back pain (n=30) and a group without low back pain (n=30)--participated in this study. METHODS: Electromyographic (EMG) and force data were obtained during a muscle fatigue test. The same test was repeated to monitor recovery. Linear regression analysis was used to obtain fatigue indexes. RESULTS: Subjects with pain produced significantly lower force values than those without pain. The use of fatigue indexes and force values permitted accurate classification in 89.5% of cases. DISCUSSION AND CONCLUSION: The results confirm that subjects with pain show early myoelectrical manifestations of muscle fatigue and that EMG can be a useful tool in the evaluation of low back pain.

Assuntos

RESUMO

The purpose of this study was to determine the validity of using the electromyography (EMG) signal as a noninvasive method of estimating the lactate threshold (LT) power output in recreational cyclists. Using an electromagnetic bicycle ergometer and constant pedaling cadence of 80 rpm, 24 recreational cyclists performed an incremental exercise protocol that consisted of stepwise increases in power output of 25 W every 3 min until exhaustion. The EMG signal was recorded from the right vastus lateralis (VL) and right rectus femoris (RF) throughout the test. Blood samples were taken from the fingertip every 3 min. The LT was determined by examining the relation between the lactate concentration and the power output using a log-log transformation model. The root mean square (RMS) value from the EMG signal was calculated for every 1-second non-superimposing window. Sets of pairs of straight regression lines were plotted and the corresponding determination coefficients (R(2)) were calculated. The intersection point of the pair of lines with the highest R(2) product was chosen to represent the EMG threshold (EMGT). The results showed that the correlation coefficients (r) between EMGT and LT were significant (p < 0.01) and high for the VL (r = 0.826) and RF (r = 0.872). The RF and VL muscles showed similar behavior during the maximal incremental test and the EMGT and LT power output were equivalent for both muscles. The validity of using EMG to estimate the LT power output in recreational cyclists was confirmed.

Assuntos