Changes produced in the intramuscular tissue via dry needling measured with magnetic resonance imaging

Abstract Introduction Myofascial trigger points are a common cause of pain and clinically observed local muscle sensitivity. The improvement associated with the muscle relaxation effect (reduction of muscle rigidity) produced by dry needling (DN) is still not well known. Thus, it is thought that the regeneration of the tissue that has been destructed by dry needling via the inflammatory process occurs with the return to normal muscle contractility. Aims The aim of this study was to identify whether the local inflammatory effect is immediately induced by DN, using magnetic resonance imaging (MRI). Material and Methods 18 asymptomatic patients were evaluated, with latent trigger points in the medial gastrocnemius (MG). We used an intergroup research design to study differences in MRI signal in the medial gastrocnemius, before and after performing DN. The MG which presented the most pain in response to pressure, was used as the experimental or intervention group, whereas the contralateral MG was used as the control group. MRI was used with signal intensity (STIR), to identify signal changes due to local inflammation. An ANOVA test was performed to analyze the influence of DN in the STIR variable and a Student's t-test for dependent samples was used to compare the perception of pain after DN. Results The STIR increased by 128.97% after DN in the experimental group. The effect of the interaction showed significant differences (F (1.34) = 235, p = 0.0001, r = 0.93). The Bonferroni post hoc tests showed significant differences [differences in means and 95% confidence interval (95%CI) = 198 (172 - 224)] signal intensity (F (1.34) = 236, p = 0.001; r = 0.93; d = 5.03). Furthermore, a significant group was found (control vs. experimental group) after controlling for the effects of the intervention (F (1.33) = 9.95, p = 0.003, r = 0.48, d = 1.10). Regarding the perception of pain in response to pressure, a significant reduction was found between the pre and post intervention measurements (t (17) = 12.40, p = 0.001, r = 0.65, d = 1.71). The Pearson's correlation coefficient did not display any correlation among any variable. Conclusion Intramuscular edema appears immediately after (1h) the application of DN, which indicates an inflammatory process with an unexpected reduction in pain perception. Our results are in line with other findings in mice which display signs of an inflammatory response after DN. A limitation of this study was the lack of further MRI measurements to detect when the edema resolved

Electromyographic Activity Evolution of Local Twitch Responses During Dry Needling of Latent Trigger Points in the Gastrocnemius Muscle: A Cross-Sectional Study

Trigger points (TrPs) are hypersensitive spots within taut bands of skeletal muscles that elicit referred pain and motor changes. Among the variety of techniques used for treating TrPs, dry needling is one of the most commonly applied interventions. The question of eliciting local twitch responses (LTRs) during TrP dry needling is unclear. Our main aim was to investigate the evolution of the electromyographic (EMG) peak activity of each LTR elicited during dry needling into latent TrPs of the gastrocnemius medialis muscle. Methods. Twenty asymptomatic subjects with latent TrPs in the gastrocnemius medialis muscle participated in this cross-sectional study. Changes in EMG signal amplitude (root mean square [RMS]) with superficial EMG were assessed five minutes before, during, and five minutes after dry needling. The peak RMS score of each LTR was calculated (every 0.5 sec). Results. Analysis of variance revealed a significant effect (F ¼ 29.069, P <0.001) showing a significant decrease of RMS peak amplitude after each subsequent LTR. Differences were significant (P <0.001) during the first three LTRs, and stable until the end of the procedure. No changes (P ¼0.958) were found for mean RMS data at rest before (mean ¼ 65.2 mv, 95% confidence interval [CI] ¼ 47.3–83.1) and after (61.0 mv, 95% CI ¼ 42.3–79.7) dry needling. Conclusions. We found that, in a series of LTRs elicited during the application of dry needling over latent TrPs in the medial gastrocnemius muscle, the RMS peak amplitude of each subsequent LTR decreased as compared with the initial RMS peak amplitude of previous LTRs. No changes in superficial EMG activity at rest were observed after dry needling of latent TrPs of the gastrocnemius medialis muscle.Ciencias de la Actividad Física y del Deport

Effects of ankle position during the Nordic Hamstring exercise on range of motion, heel contact force and hamstring muscle activation

One of the main benefits of the Nordic Hamstring Exercise (NHE) is that it can be performed without the need of any extra material. However, numerous technical execution variables such as the ankle and pelvis position can influence the performance. The primary aims of this study were to investigate the effects of ankle position (i.e., plantar or dorsal flexion) on Nordic Hamstring Break Point (NHBP), repetition time and heel contact force. A secondary aim was to investigate differences in biceps femoris long head and semitendinosus muscle activation. Male professional field hockey players (n = 12) volunteered for the study. Paired t-tests were used to analyse the effect of ankle position on muscle NHBP, eccentric peak torque and repetition time. Ankle dorsal flexion resulted in a higher NHBP (p = 0.002, effect size [ES] = 1.48 [0.57 to 2.38]), repetition time (p = 0.004, ES = 0.98 [0.24 to 1.72]) and both absolute and relative heel contact force (p = 0.028, ES = 0.67 [0.01 to 1.34], p = 0.017, ES = 0.76 [0.07 to 1.44], respectively) compared to plantar flexion. Muscle activation was not significant different. This study showed a higher NHBP, absolute and relative heel contact force and repetition time with a dorsal flexed ankle vs. a plantar flexed ankle in the NHE, without changes in hamstrings muscle activation

The effects of the Nordic hamstring exercise on sprint performance and eccentric knee flexor strength: A systematic review and meta-analysis of intervention studies among team sport players

Objectives: The primary aim of this study was to investigate the effects of the Nordic hamstring exercise (NHE) on sprint performance (i.e., 5, 10 and 20 m) and explore associations between study characteristics and sprint outcomes in team sport players. Secondary aims were to (1) investigate the effects of the NHE on eccentric strength of the knee flexors (ESKF) with categorical subgroup analysis to determine differences between recreationally, well-trained individuals and young athletes, (2) determine the relation between ESKF and sprint performance in team sport players, and (3) explore the effect of study characteristics (i.e., weekly volume, time duration and body mass) on ESKF.Methods: Electronic databases were searched until the 20th of June 2020. 17 studies met the inclusion criteria. Random-effects meta-analyses were used to determine the mean difference (MD) or standardized change of mean difference (SCMD) between NHE and control group for sprint time and ESKF, respectively.Results: NHE interventions showed a positive effect on sprint performance (-0.04 s [-0.08, -0.01]). Sub-group meta-analyses indicated no significant differences in 5 and 20 m sprint performance (MDsprint(5m)= -0.02 s [-0.10, 0.06]) and (MD (sprint(20m))= -0.05 s [-0.30, 0.19]), respectively. A significant difference was however found for 10 m sprint performance (MDsprint(10m) = -0.06 s [-0.10, -0.01]). Meta-analysis on the effects of the NHE on ESKF showed a significant benefit of 0.83 SCMD [0.55, 1.12] in favour of the intervention group.Conclusions: Studies with some concerns or high risk of bias show that training programs involving the NHE can have small beneficial effects on sprint performance in team sport players. Studies with some concerns or high risk of bias showed moderate beneficial effects on ESKF among a sample of relatively untrained individuals. However, for well-trained team sport players, the improvements in ESKF were less consistent, suggesting a higher training intensity during the NHE may be required to induce adaptations. (C) 2021 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved