Paul W. M Marshall

The validity and reliability of surface EMG to assess the neuromuscular response of the abdominal muscles to rapid limb movement

The transversus abdominus muscle (TrA) has been demonstrated to be active prior to rapid movements of the upper and lower limbs. This activity is termed feed forward motivation. The lack of feed-forward activation for TrA has been demonstrated in subjects with low back pain. The measures used for investigation of TrA function have been fine-wire needle EMG. This limits the practical application of TrA study due to the cost and level of specialisation required for this technique. The objective of the current study was to investigate the validity and reliability of using a surface EMG site to replicate the findings for the feed-forward activation of TrA prior to rapid limb movement. A population of healthy, young males (n = 20) were studied and it was found that four of the subjects did not meet feed-forward criteria. These results were shown to be highly reliable after a 2-week period for the TrA/IO site only. The validity of the signal was further investigated using several functional tasks to specifically target muscles of the abdominal region. Using a cross-correlation analysis to evaluate crosstalk from adjacent muscles, it was concluded that the signal representing TrA/IO accurately demonstrates the functional activity of the muscle. This study has demonstrated a viable surface EMG method to evaluate the feed-forward activation of TrA/IO prior to rapid limb movement. This may lead to opportunities for the clinical application of this method. It was also a finding of this study that four asymptomatic subjects did not pre-activate, therefore providing a rationale for future prospective investigations on whether the lack of TrA/IO feed-forward activation is a cause or an effect of low back pain.

Increased deltoid and abdominal muscle activity during Swiss ball bench press.

The swiss is widely used in the recreational training environment as a supplement to conventional resistance training. One such application is to use the swiss ball as a bench support for bench press exercise. There is no evidence to indicate that the use of a swiss ball is beneficial for resistance training exercise. This study investigated muscle activity using surface electromyography of upper-body and abdominal muscles during the concentric and eccentric phases of the bench press on and off a swiss ball. Volunteers for this study were 14 resistance-trained subjects who performed isolated concentric and eccentric bench press repetitions using the 2 test surfaces with a 2-second cadence at a load equivalent to 60% maximum force output. The average root mean square of the muscle activity was calculated for each movement, and perceived exertion during the tasks was collected using a Borg Scale. The results of the study showed that deltoid and abdominal muscle activity was increased for repetitions performed using the swiss ball. Increased deltoid muscle activity supports previous findings for increased activity when greater instability is introduced to the bench press movement. Abdominal muscle activity increases were not hypothesized, but this finding provides scientific evidence for anecdotal reasoning behind swiss ball use as a potential core stability training device.

A randomized controlled trial for the effect of passive stretching on measures of hamstring extensibility, passive stiffness, strength, and stretch tolerance

To measure hamstring extensibility, stiffness, stretch tolerance, and strength following a 4-week passive stretching program. Randomized controlled trial. Twenty-two healthy participants were randomly assigned to either a 4-week stretching program consisting of 4 hamstring and hip stretches performed 5 times per week, or a non-stretching control group. Hamstring extensibility and stiffness were measured before and after training using the instrumented straight leg raise test (iSLR). Stretch tolerance was measured as the pain intensity (visual analog scale; VAS) elicited during the maximal stretch. Hamstring strength was measured using isokinetic dynamometry at 30 and 120° s(-1). Hamstring extensibility increased by 20.9% in the intervention group following 4 weeks of training (p<0.001; d=0.86). Passive stiffness was reduced by 31% in the intervention group (p<0.05; d=-0.89). Stretch tolerance VAS scores were not different between groups at either time point, and no changes were observed following training. There were no changes in hamstring concentric strength measured at 30 and 120° s(-1). Passive stretching increases hamstring extensibility and decreases passive stiffness, with no change in stretch tolerance defined by pain intensity during the stretch. Compared to previous research, the volume of stretching was higher in this study. The volume of prescribed stretching is important for eliciting the strong clinical effect observed in this study.

Fifteen Minutes of Chair-Based Yoga Postures or Guided Meditation Performed in the Office Can Elicit a Relaxation Response

This study compared acute (15 min) yoga posture and guided meditation practice, performed seated in a typical office workspace, on physiological and psychological markers of stress. Twenty participants (39.6 ± 9.5 yr) completed three conditions: yoga, meditation, and control (i.e., usual work) separated by ≥24 hrs. Yoga and meditation significantly reduced perceived stress versus control, and this effect was maintained postintervention. Yoga increased heart rate while meditation reduced heart rate versus control (P < 0.05). Respiration rate was reduced during yoga and meditation versus control (P < 0.05). Domains of heart rate variability (e.g., SDNN and Total Power) were significantly reduced during control versus yoga and meditation. Systolic and diastolic blood pressure were reduced secondary to meditation versus control only (P < 0.05). Physiological adaptations generally regressed toward baseline postintervention. In conclusion, yoga postures or meditation performed in the office can acutely improve several physiological and psychological markers of stress. These effects may be at least partially mediated by reduced respiration rate.

The effectiveness of Pilates exercise in people with chronic low back pain : a systematic review

Objective To evaluate the effectiveness of Pilates exercise in people with chronic low back pain (CLBP) through a systematic review of randomised controlled trials (RCTs). Data Sources A search for RCTs was undertaken using Medical Search Terms and synonyms for “Pilates” and “low back pain” within the maximal date range of 10 databases. Databases included the Cumulative Index to Nursing and Allied Health Literature; Cochrane Library; Medline; Physiotherapy Evidence Database; ProQuest: Health and Medical Complete, Nursing and Allied Health Source, Dissertation and Theses; Scopus; Sport Discus; Web of Science. Study Selection Two independent reviewers were involved in the selection of evidence. To be included, relevant RCTs needed to be published in the English language. From 152 studies, 14 RCTs were included. Data Extraction Two independent reviewers appraised the methodological quality of RCTs using the McMaster Critical Review Form for Quantitative Studies. The author(s), year of publication, and details regarding participants, Pilates exercise, comparison treatments, and outcome measures, and findings, were then extracted. Data Synthesis The methodological quality of RCTs ranged from “poor” to “excellent”. A meta-analysis of RCTs was not undertaken due to the heterogeneity of RCTs. Pilates exercise provided statistically significant improvements in pain and functional ability compared to usual care and physical activity between 4 and 15 weeks, but not at 24 weeks. There were no consistent statistically significant differences in improvements in pain and functional ability with Pilates exercise, massage therapy, or other forms of exercise at any time period. Conclusions Pilates exercise offers greater improvements in pain and functional ability compared to usual care and physical activity in the short term. Pilates exercise offers equivalent improvements to massage therapy and other forms of exercise. Future research should explore optimal Pilates exercise designs, and whether some people with CLBP may benefit from Pilates exercise more than others.

Effectiveness of Pilates exercise in treating people with chronic low back pain: a systematic review of systematic reviews

BackgroundSystematic reviews provide clinical practice recommendations that are based on evaluation of primary evidence. When systematic reviews with the same aims have different conclusions, it is difficult to ascertain which review reported the most credible and robust findings.MethodsThis study examined five systematic reviews that have investigated the effectiveness of Pilates exercise in people with chronic low back pain. A four-stage process was used to interpret findings of the reviews. This process included comparison of research questions, included primary studies, and the level and quality of evidence of systematic reviews. Two independent reviewers assessed the level of evidence and the methodological quality of systematic reviews, using the National Health and Medical Research Council hierarchy of evidence, and the Revised Assessment of Multiple Systematic Reviews respectively. Any disagreements were resolved by a third researcher.ResultsA high level of consensus was achieved between the reviewers. Conflicting findings were reported by the five systematic reviews regarding the effectiveness of Pilates in reducing pain and disability in people with chronic low back pain. Authors of the systematic reviews included primary studies that did not match their questions in relation to treatment or population characteristics. A total of ten primary studies were identified across five systematic reviews. Only two of the primary studies were included in all of the reviews due to different inclusion criteria relating to publication date and status, definition of Pilates, and methodological quality. The level of evidence of reviews was low due to the methodological design of the primary studies. The methodological quality of reviews varied. Those which conducted a meta-analysis obtained higher scores.ConclusionThere is inconclusive evidence that Pilates is effective in reducing pain and disability in people with chronic low back pain. This is due to the small number and poor methodological quality of primary studies. The Revised Assessment of Multiple Systematic Reviews provides a useful method of appraising the methodological quality of systematic reviews. Individual item scores, however, should be examined in addition to total scores, so that significant methodological flaws of systematic reviews are not missed, and results are interpreted appropriately. (348 words)

Effect of an office worksite-based yoga program on heart rate variability: outcomes of a randomized controlled trial

BackgroundChronic work-related stress is an independent risk factor for cardiometabolic diseases and associated mortality, particularly when compounded by a sedentary work environment. The purpose of this study was to determine if an office worksite-based hatha yoga program could improve physiological stress, evaluated via heart rate variability (HRV), and associated health-related outcomes in a cohort of office workers.MethodsThirty-seven adults employed in university-based office positions were randomized upon the completion of baseline testing to an experimental or control group. The experimental group completed a 10-week yoga program prescribed three sessions per week during lunch hour (50 min per session). An experienced instructor led the sessions, which emphasized asanas (postures) and vinyasa (exercises). The primary outcome was the high frequency (HF) power component of HRV. Secondary outcomes included additional HRV parameters, musculoskeletal fitness (i.e. push-up, side-bridge, and sit & reach tests) and psychological indices (i.e. state and trait anxiety, quality of life and job satisfaction).ResultsAll measures of HRV failed to change in the experimental group versus the control group, except that the experimental group significantly increased LF:HF (p = 0.04) and reduced pNN50 (p = 0.04) versus control, contrary to our hypotheses. Flexibility, evaluated via sit & reach test increased in the experimental group versus the control group (p < 0.001). No other adaptations were noted. Post hoc analysis comparing participants who completed ≥70% of yoga sessions (n = 11) to control (n = 19) yielded the same findings, except that the high adherers also reduced state anxiety (p = 0.02) and RMSSD (p = 0.05), and tended to improve the push-up test (p = 0.07) versus control.ConclusionsA 10-week hatha yoga intervention delivered at the office worksite during lunch hour did not improve HF power or other HRV parameters. However, improvements in flexibility, state anxiety and musculoskeletal fitness were noted with high adherence. Future investigations should incorporate strategies to promote adherence, involve more frequent and longer durations of yoga training, and enrol cohorts who suffer from higher levels of work-related stress.Trial registrationACTRN12611000536965

Delayed abdominal muscle onsets and self-report measures of pain and disability in chronic low back pain ☆

OBJECTIVE The objective of this study was the measure the onset time of the transverse abdominis (TA) muscle during rapid unilateral shoulder movements in individuals with chronic low back pain (LBP), and to evaluate the relationship between latency times and self-report measures of pain and disability. DESIGN Descriptive cross-sectional study. SETTING University laboratory. PARTICIPANTS Eighty individuals with chronic LBP of a non-specific origin (males n=44, females n=36). MAIN OUTCOME MEASURES Responses of the right and left surface TA/internal obliques were measured using surface electromyography (EMG) during rapid unilateral shoulder flexion, abduction, and extension. Pain intensity was measured using a visual analog scale (VAS), and disability with the Oswestry disability index (ODI). RESULTS Seventy-five percent of individuals were identified as lacking feedforward activation. A significant sidexdirection main effect was identified, with the ipsilateral latency more delayed in flexion and abduction (F(2316)=58.2, p<0.001). Individuals without feedforward activation had lower ODI scores (23.2+/-6.9% vs 31.0+/-9.2%, mean difference 7.8%, 95% CI 3.9 to 11.6%, p<0.001). Regression analysis found that 17% of the variance in VAS scores for the entire sample (n=80) were explained by the latency times measured. This relationship was stronger when the sample was separated into individuals who did (n=20), and did not (n=60) have feedforward activation. CONCLUSION Deep abdominal muscle onsets during rapid limb movement were significantly associated with self-rated pain scores. Seventy-five percent of individuals with chronic non-specific LBP exhibited delayed activation. No evidence has been provided in this study to support, or refute the use of specific localized deep abdominal contractions for exercise rehabilitation programs.

Changes in the flexion relaxation response following an exercise intervention.

Study Design. Pre and post 12-week training study using surface electromyography to measure the flexion relaxation response. Objective. To evaluate whether the active or passive phases of the flexion relaxation measurement changes following an exercise intervention in patients with low back pain. Summary of Background Data. Impaired neuromuscular activation is an area of specific interest in patients with chronic nonspecific low back pain (LBP). The flexion relaxation phenomenon is commonly measured in LBP patients; however, there is insufficient evidence about the changes in this measure following an intervention. Methods. Fifteen subjects with chronic LBP (7 females, 8 males) performed a 12-week training intervention. The main outcome measures were the Oswestry disability index, visual analog scale, and flexion relaxation response analyzed by the raw electromyograph (EMG) signal, the relative EMG signal, and the flexion relaxation ratio. Results. Disability and pain scores improved significantly after the 12-week intervention. There were no changes in the active components of the flexion relaxation measurement but an approximate 67% decrease in the amount of activity measured during the relaxation phase at full trunk flexion. Conclusion. The data suggest that afferent feedback changes may be explaining why there is improved electrical relaxation following an exercise intervention.

Hamstring Muscle Fatigue and Central Motor Output during a Simulated Soccer Match

Purpose To examine changes in hamstring muscle fatigue and central motor output during a 90-minute simulated soccer match, and the concomitant changes in hamstring maximal torque and rate of torque development. Method Eight amateur male soccer players performed a 90-minute simulated soccer match, with measures performed at the start of and every 15-minutes during each half. Maximal torque (Nm) and rate of torque development (RTD; Nm.s–1) were calculated from maximal isometric knee flexor contractions performed at 10° of flexion. Hamstring peripheral fatigue was assessed from changes in the size and shape of the resting twitch (RT). Hamstring central motor output was quantified from voluntary activation (%) and normalized biceps femoris (BF) and medial hamstrings (MH) electromyographic amplitudes (EMG/M). Results Maximal torque was reduced at 45-minutes by 7.6±9.4% (p<0.05). RTD in time intervals of 0–25, 0–50, and 0–75 ms post-contraction onset were reduced after 15-minutes in the first-half between 29.6 to 46.2% (p<0.05), and were further reduced at the end of the second-half (p<0.05). Maximal EMG/M was reduced for biceps femoris only concomitant to the time-course of reductions in maximal torque (p = 0.007). The rate of EMG rise for BF and MH was reduced in early time periods (0–75 ms) post-contraction onset (p<0.05). No changes were observed for the size and shape of the RT, indicating no hamstring peripheral fatigue. Conclusion Centrally mediated reductions in maximal torque and rate of torque development provide insight into factors that may explain hamstring injury risk during soccer. Of particular interest were early reductions during the first-half of hamstring rate of torque development, and the decline in maximal EMG/M of biceps femoris in the latter stages of the half. These are important findings that may help explain why the hamstrings are particularly vulnerable to strain injury during soccer.