ABSTRACT
Spinal manipulation is a manual treatment technique that delivers a thrust, using specific biomechanical parameters to exert its therapeutic effects. These parameters have been shown to have a unique dose-response relationship with the physiological responses of the therapy. So far, however, there has not been a unified approach to standardize these biomechanical characteristics. In fact, it is still undetermined how they affect the observed clinical outcomes of spinal manipulation. This study, therefore, reviewed the current body of literature to explore these dosage parameters and evaluate their significance, with respect to physiological and clinical outcomes. From the experimental studies reviewed herein, it is evident that the modulation of manipulation's biomechanical parameters elicits transient physiological responses, including changes in neuronal activity, electromyographic responses, spinal stiffness, muscle spindle responses, paraspinal muscle activity, vertebral displacement, and segmental and intersegmental acceleration responses. However, to date, there have been few clinical trials that tested the therapeutic relevance of these changes. In addition, there were some inherent limitations in both human and animal models due to the use of mechanical devices to apply the thrust. Future studies evaluating the effects of varying biomechanical parameters of spinal manipulation should include clinicians to deliver the therapy in order to explore the true clinical significance of the dose-response relationship.
Subject(s)
Animals , Humans , Manipulation, SpinalABSTRACT
The aim of this study was to investigate longitudinal changes in rate for development (RFD) during the early, late, and whole phases, and to determine whether early RFD is exhibited in response to the improvement of explosive force production in training throughout the competitive season. Fifteen male jumpers participated in personal training according to the training cycle (Semi-annual two-cycle periodization model) of their team. The early, late and average RFD along with peak force during isometric single-leg press with a knee angle of 115° were measured. The measurement was performed during the pre-season (January or March) and post-season (September or November). Based on comparison between the two measurements, it was found that 10 participants displayed improved performance in the major jump event. The average RFD increased significantly for all participants (p = 0.02, d = 0.67). Participants who achieved their personal best had seen a significant increase in early RFD (p = 0.03, d = 0.84). In the contrast, late RFD (all participants; p = 0.06, d = 0.54, participants who achieved personal best; p = 0.07, d = 0.65) and peak force (all participants; p = 0.31, d = 0.27, participants who achieved personal best; p = 0.15, d = 0.50) did not show significant changes. These results suggested that changes in early, late, and average RFD varied respectively. Moreover, early RFD was found to be the best indicator that reflects improved jumping performance through explosive force production compared to late RFD, average RFD, and peak force.
ABSTRACT
O objetivo deste estudo foi investigar, em mulheres idosas, o efeito agudo do alongamento estático sobre a taxa de desenvolvimento de força pico (TDFP) e contração voluntária máxima (CVM). A amostra foi composta por 10 mulheres idosas (idade 68,5 ± 7,0 anos; peso 70,9 ± 8,1 kg; estatura 159,4 ± 6,0 cm; índice de massa corporal 28,0 ± 3,8 kg/m2). A TDFP e a CVM foram testadas no exercício Leg Press, antes e após as condições controle ou alongamento (três séries de 30 segundos de alongamento estático do quadríceps femoral), em dois dias diferentes (24 horas de intervalo). A TDFP foi determinada como a inclinação mais íngreme da curva, calculada dentro da janela regular de 20 ms (?Força/?Tempo), para os primeiros 200 ms após o início da força muscular. A CVM foi determinada como o maior ponto registrado na tentativa. Em cada dia, apenas uma condição foi testada e a ordem de emprego para cada condição foi determinada aleatoriamente. A intensidade do alongamento foi determinada pelo limiar de dor muscular. Quatro avaliações pós-condições (pós-tratamento; 10; 20 e 30 minutos) foram realizadas para acompanhar o comportamento da força muscular. A ANCOVA 2x5, seguida do teste post-hoc de Scheffé, não mostrou interações, condição vs. momento, significativas (P > 0,05) para a TDFP e CVM. Em conclusão, séries agudas de alongamento estático para o quadríceps femoral não afetam a capacidade de produzir força muscular rapidamente e máxima de mulheres idosas.
The objective of this study was to investigate the acute effect of static stretching on the peak rate of force development (PRFD) and maximum voluntary contraction (MVC) in older women. Ten women (68.5 ± 7.0 years; 70.9 ± 8.1 kg; 159.4 ± 6.0 cm; body mass index: 28.0 ± 3.8 kg/m2) were studied. MVC and PRFD were determined by leg press exercise before and after the control or stretching condition (three sets of 30 seconds of static stretching of the quadriceps) on two different days (interval of 24 hours). PRFD was determined as the steepest slope of the curve, calculated within regular windows of 20 milliseconds (?force/?time) for the first 200 milliseconds after the onset of contraction. MVC was determined as the highest value recorded in each set. Only one condition was tested on each day and the order of application of each condition was determined randomly. The stretching intensity was evaluated by the muscle pain threshold. Four post-condition assessments (post-treatment, 10, 20, and 30 minutes) were performed to monitor muscle strength. ANCOVA 2x5, followed by the Scheffé post-hoc test, showed no significant interactions between conditions vs. times (P > 0.05) for PRFD or MVC. In conclusion, acute bouts of static stretching of the quadriceps femoris do not affect the ability of rapid and maximum muscle force production in older women.
ABSTRACT
The evaluation of muscular power function has been mainly limited to dynamic contraction, but force-time parameters in static explosive contraction may be useful. The purpose of this study was to examine the trial-to-trial differences of exertion pattern and the reliability of the force-time parameters in the development phase of static maximal explosive grip (SEG) using seventy healthy young male subjects (age 18.8±2.3yr) . In SEG measurement, subjects were instructed to exert maximal isometric force with a dominant hand as fast and forcefully as possible. Data was collected from two trials with 3 minutes rest between trials. Eleven variables (time to fixed level, average force, integrated area, maximal rate of force development, and equivalent for mechanical power parameter) were selected as force-time parameters.<BR>The reliability of maximal grip strength (MAX) was very high (ICC=0.944, p<0.05) . In the above-stated instruction condition, the trial-to-trial difference expanded from 0.1- 0.4 sec, then re-duced in the vicinity of MAX during SEG exertion. Significant differences, however, were not found at any exertion time and reproducibility of SEG exertion pattern was very high between the two trials. The trial-to-trial reliability in all force-time parameters was significant (ICC=0.346-0.878, p<0.05) .<BR>Reliability of the parameters measuring the earlier phase (about 0.1-0.5 sec) was low or moderate (ICC<0.7), while reliability of the parameters measuring the MAX vicinity tended to be high. The MAX relationship to force-time parameters in the MAX vicinity is high, but is low or moderate for the other parameters. It was suggested that the force-time parameters in the vicinity of MAX in SEG exertion might be useful for evaluating static power function in a clinical setting.