How and why do people with chronic low back pain modify their physical activity? A mixed-methods survey.

BACKGROUND: This study investigated the impact of Chronic Low Back Pain (CLBP) on individuals' physical activity (PA) behaviours, specifically, how they modify, cease, or continue PA when experiencing CLBP. The primary aim was to explore the relationship between CLBP and PA and how this is influenced in different contexts (e.g., necessity of a task). METHODS: A mixed-methods survey was administered to 220 participants, including self-reported outcomes, and capturing responses to three distinct questions related to PA and CLBP. The data was analysed via a content analysis. RESULTS: The findings revealed that individuals with CLBP are most likely to modify PA in work-related contexts and least likely to cease it in the same setting. Housework emerged as the most common domain for cessation of PA, while work/study activities were predominantly continued. Reasons for these trends were typically task-based rather than health or enjoyment based and influenced by the perceived necessity of the task in question. CONCLUSION: The study highlights the role of occupational and educational settings in individual responses to CLBP. The findings also highlight a gap in public awareness regarding effective CLBP management strategies, emphasising the need for increased education and awareness programs.

Are Exercise Interventions in Clinical Trials for Chronic Low Back Pain Dosed Appropriately to Meet the World Health Organization's Physical Activity Guidelines?

OBJECTIVE: This study aimed to estimate the proportion of exercise interventions tested in clinical trials of people with chronic low back pain (CLBP) that meet the World Health Organization's (WHO) physical activity guidelines. METHODS: A secondary analysis of the 2021 Cochrane review of exercise therapy for CLBP was performed. Data from each study were extracted by 1 reviewer and were checked by a second reviewer. Data extracted related to the frequency, duration and intensity of each exercise intervention, and the proportion of exercise interventions that met the WHO's physical activity guidelines (aerobic, muscle strengthening, or both) were determined. RESULTS: The 249 included trials comprised 426 exercise interventions. Few interventions reported an exercise type and dose consistent with the WHO guidelines (aerobic: 1.6%, muscle strengthening: 5.6%, both: 1.6%). Poor reporting of exercise intensity limited our ability to determine whether interventions met the guidelines. CONCLUSION: Few interventions tested in clinical trials for people with CLBP prescribe an exercise type and dose consistent with the WHO guidelines. Therefore, they do not appear sufficiently dosed to achieve broader health outcomes. Future trials should investigate the effect of WHO guideline-recommended exercise interventions on patient-reported outcomes (pain and disability) as well as health-related outcomes in people with CLBP. IMPACT: This exploratory analysis showed the lack of exercise interventions in the CLBP literature that meet the WHO's physical activity guidelines. With people in chronic pain groups, such as people with CLBP, being at higher risk for noncommunicable disease, it appears this is a key consideration for exercise practitioners when designing interventions for people with CLBP.

Scheduling Concurrent Training 48 versus 72 h after Simulated Match Play: Effects on Neuromuscular Function and Fatigue.

INTRODUCTION: Scheduling concurrent training (CT) during the in-season microcycle in field-based team sport is driven by prematch and postmatch recovery. This study examined the neuromuscular function, fatigue, and soreness responses to CT administered 48 h (match day (MD) + 2) versus 72 h (MD + 3) after match. METHODS: Ten male recreational-level team sport athletes were monitored daily during two 5-d microcycles, which began with a simulated match (Soccer-specific Aerobic Field Test (SAFT90)) and CT performed either 48 or 72 h after match. Maximal voluntary force, quadriceps maximum EMG, voluntary activation, muscle contractile function (evoked twitch responses), muscle soreness, and fatigue were assessed immediately before and after the SAFT90, and every 24 up to 96 h after match. Outcome measures were also assessed immediately after CT. The CT consisted of an intermittent sprint protocol and a lower limb resistance training session separated by 1 h. RESULTS: Immediately after the SAFT90 in both conditions, maximal voluntary force was below baseline (mean change (Δ), -14.6% ± 10.0%; P = 0.03), recovering 48 h post. Quadriceps contractile function (Δ, -31.5% ± 11.4%; P = 0.003) and voluntary activation (Δ, -8.9 ± 6.2%; P = 0.003) were also hampered after the SAFT90, recovering 24 h post in both conditions. In addition, the SAFT90 elicited elevated levels of fatigue and muscle soreness that recovered 24 h after the SAFT90 before increasing at 72 and 96 h post in the MD + 2 and MD + 3 conditions, respectively. CONCLUSIONS: Recovery of fatigue was only observed at the end of the microcycle when CT was prescribed on MD + 2. Therefore, CT scheduled early (MD + 2) in the microcycle might avoid compromising forthcoming match preparation.

Reductions in movement-associated fear are dependent upon graded exposure in chronic low back pain: An exploratory analysis of a modified 3-item fear hierarchy.

OBJECTIVE: To explore the effectiveness of a modified fear hierarchy on measuring improvements in movement-associated fear in chronic low back pain. METHODS: A modified 3-item fear hierarchy was created and implemented based on principles of graded exposure. This study was an exploratory analysis of the modified 3-item fear hierarchy from a larger clinical trial data set. Both groups received pain education and exercise, either bodyweight or strength training. Both groups performed item one on the hierarchy, the squat. Only the strength training group performed item 2, the deadlift. Neither group performed item 3, the overhead press. Analysis of Covariance and stepwise linear regression were used to explore results. RESULTS: Improvement in movement-associated fear was conditional upon graded exposure. Both groups improved in the squat movement (p ≤ 0.05), which both performed. Only the strength training group improved in the deadlift (p ≤ 0.01), and neither improved in the overhead press (p ≥ 0.05). CONCLUSION: Reductions in movement-associated fear are conditional upon graded exposure, based on the use of a novel modified 3-item fear hierarchy. Further research is needed to understand the utility of this tool in a patient-led approach to co-designing a graded exposure-based intervention.

The effect of exercise engagement on low back disability at 12-months is mediated by pain and catastrophizing in a community sample of people with chronic low back pain.

Despite being a first-line treatment recommendation, there is uncertainly for how exercise helps people with chronic low back pain. We designed this study to examine how exercise might help people with chronic low back pain by following a large community sample for 1-year. Qualitative questionnaires and self-report measures were collected every 3-months for 1-year in 400 people with chronic low back pain. People were not provided any specific treatment advice as part of this study but were allowed to engage with any normal physical activity, treatment, or medication as part of their normal life. Exercise engagement was defined from inspection of participant qualitative responses, according to minimum acceptable levels of exercise that elicit symptom reduction. Multiple mediation analysis was performed to examine the effect of exercise engagement on disability through the proposed mediators (pain, fear, catastrophizing, depression, anxiety, self-efficacy). The significant effect of exercise engagement on reductions in disability at 6- and 12-months was explained through pain and catastrophizing. People with chronic low back pain who reported worsening of symptoms over the year had similar reporting of exercise throughout the 12-months to people who had improvements in disability. Exercise can reduce disability through the effect on pain and catastrophizing, but how this effect occurs (i.e., an active or passive component of exercise) is unclear.

Does a powerlifting inspired exercise programme better compliment pain education compared to bodyweight exercise for people with chronic low back pain? A multicentre, single-blind, randomised controlled trial.

BACKGROUND: Contemporary management of chronic low back pain involves combined exercise and pain education. Currently, there is a gap in the literature for whether any exercise mode better pairs with pain education. The purpose of this study was to compare general callisthenic exercise with a powerlifting style programme, both paired with consistent pain education, for chronic low back pain. We hypothesised powerlifting style training may better compliment the messages of pain education. METHODS: An 8-week single-blind randomised controlled trial was conducted comparing bodyweight exercise (n = 32) with powerlifting (n = 32) paired with the same education, for people with chronic low back pain. Exercise sessions were one-on-one and lasted 60-min, with the last 5-15 min comprising pain education. Pain, disability, fear, catastrophizing, self-efficacy, anxiety, and depression were measured at baseline, 8-weeks, 3-months, and 6-months. RESULTS: No significant between-group differences were observed for pain (p≥0.40), or disability (p≥0.45) at any time-point. Within-group differences were significantly improved for pain (p ≤ 0.04) and disability (p ≤ 0.04) at all time-points for both groups, except 6-month disability in the bodyweight group (p = 0.1). Behavioural measures explained 39-60% of the variance in changes in pain and disability at each time-point, with fear and self-efficacy emerging as significant in these models (p ≤ 0.001). CONCLUSIONS: Both powerlifting and bodyweight exercise were safe and beneficial when paired with pain education for chronic low back pain, with reductions in pain and disability associated with improved fear and self-efficacy. This study provides opportunity for practitioners to no longer be constrained by systematic approaches to chronic low back pain.

Fatigability of the knee extensors following high- and low-load resistance exercise sessions in trained men.

PURPOSE: Fatigability after gym-based resistance exercises with high and low loads has not been well described, thus limiting the translation of exhaustive low-weight prescription into athletic practice. We compared the fatigability and recovery of the knee extensor muscles for up to 1H after sessions that involved either high- or low-load resistance exercises. METHODS: 16 trained men performed two resistance exercise sessions between 5 and 7 days apart. The LIGHT session involved five sets to task failure at 50% of maximal knee-extension strength, whereas the HEAVY session accrued repetitions across seven sets at intensities ≥ 80% maximal knee-extension strength. Measures of quadriceps maximal torque and rate of torque development were measured before, after, and 1H after each exercise session. Muscle activation (electromyography and voluntary activation) and contractility were measured from doublet stimulation of the femoral nerve during and after maximal contractions, respectively. RESULTS: Greater declines in maximal rate of torque development were observed after the LIGHT compared with the HEAVY session (p < 0.001), with full recovery after 1H. Voluntary activation (100-Hz doublet stimulation) and surface electromyograms were reduced immediately after the HEAVY session only (p < 0.05), with greater declines in quadriceps twitch amplitudes after the LIGHT session (p < 0.01). Voluntary activation (100-Hz doublet stimulation) was reduced at 1H after both the HEAVY and LIGHT sessions (p < 0.05). CONCLUSIONS: Despite differences in the decreases in muscle activation and contractility after high- and low-load resistance-exercise sessions, recovery of neuromuscular function was essentially complete after 1H of rest for both sessions.

Acute Neuromuscular Response to Team Sports-Specific Running, Resistance, and Concurrent Training: A Crossover Study.

PURPOSE: This study aimed to examine the changes in muscle contractile function, voluntary activation, and muscle damage after lower limb resistance training (RT), intermittent sprint exercise, and concurrent training (CT). METHODS: Ten male, recreational team sport athletes with a history of RT participated in a randomized crossover study involving an intermittent sprint protocol (ISP), lower limb RT, and CT (ISP and RT separated by 1 h). Before (PRE), immediately after (POST), 24 h and 48 h after each exercise condition, quadriceps muscle activation, voluntary activation, muscle contractile function (evoked twitch responses), creatine kinase, muscle soreness, and Profile of Mood States (POMS)-fatigue were recorded. RESULTS: Quadriceps contractile function was hampered in all conditions, with a significantly greater decline observed POST RT (58.4% ± 18.0%) and CT (54.8% ± 8.6%) compared with ISP (35.9% ± 10.7%, P < 0.05), recovering at 48 h after all exercise conditions. POMS-fatigue ratings increased at POST in all conditions with CT and ISP eliciting the greatest increase, returning to baseline 48 h after all exercise conditions. Quadriceps muscle soreness remained elevated from PRE at 48 h after all exercise conditions. No changes across time were observed for voluntary activation and quadriceps surface EMG amplitude after any exercise condition. The volume and load lifted in the RT session was unaffected by previous intermittent exercise (ISP) in CT. CONCLUSIONS: RT impairs contractile function, which is not exacerbated when performed 1 h after the ISP. Contractile function after all exercise conditions displayed the same recovery profile (48 h) despite the postexercise decrement being smaller after the ISP compared with RT and CT. Previous intermittent sprint exercise does not negatively affect the volume of exercise performed in a lower limb RT session.

The Moderating Effect of Treatment Engagement on Fear-avoidance Beliefs in People With Chronic Low Back Pain.

OBJECTIVES: The fear-avoidance model (FAM) is used to explain pain-related disability and design targeted interventions for people with chronic low back pain. While treatment engagement is critical, it is unknown how treatment moderates the FAM. METHODS: This study examined whether pathways within the FAM were moderated by treatment engagement in 508 people with chronic low back pain. Measures of disability, pain, fear, catastrophizing, anxiety, depression, and self-efficacy were collected through self-report, and descriptors of treatment engaged within the last month (physical activity type, medication, allied and medical health practitioner). Moderated mediation analyses were performed to examine the conditional effect of treatment engagement on fear-avoidance pathways. RESULTS: The conditional effect of anxiety on disability was only significant for people who did not report any treatment engagement in the last month (B=1.03, 95% confidence interval: 0.53-1.53, P<0.001). The effect of depression increased for people reporting more different types of treatment in the last month (1 level of treatment increase, B=0.27, 95% confidence interval: 0.05-0.50, P=0.019). Conversely, greater treatment engagement had a positive influence on the mediating effect of self-efficacy. That is, the effect of pain on efficacy reduced with greater treatment engagement, with a concomitant increased effect of self-efficacy on disability. DISCUSSION: Clinicians should explore the history and rationale behind patient treatment seeking behavior to ensure this is not reinforcing the negative effects of depressive symptoms on pain-related disability.

Fatigue, pain, and the recovery of neuromuscular function after consecutive days of full-body resistance exercise in trained men.

PURPOSE: This study measured the self-reported level of fatigue, pain, and neuromuscular function of the knee extensor muscles over a three-day period that included two consecutive days of full-body resistance exercises. METHODS: 10 resistance-trained men performed two consecutive days of full-body resistance exercise. Muscle activation (electromyography and voluntary activation), contractility, and presynaptic inhibition of Ia afferents (homosynaptic and GABA mediated presynaptic inhibition) for the quadriceps were examined from femoral and posterior tibial nerve stimulation. RESULTS: Fatigue and pain were elevated after Day 1, and were not reduced to pre-exercise levels at the start of Day 2 (p < 0.05). Maximal voluntary torque (- 51.4 Nm, 95% CI = 12.4-90.4 Nm, p = 0.005) and rate of torque development (- 469 Nm.s-1, 95% CI = 109-829 Nm.s-1, p = 0.006) were reduced after Day 1, had recovered by Day 2, and did not change after the second training session. The maximal amplitude and rate of rise for the quadriceps twitch were reduced after both training sessions (p < 0.01), with recovery 24 h each session. The maximal amplitude and rate of early muscle activation were reduced after Day 1 (p < 0.01), but no changes were observed for voluntary activation, H-reflex size and shape, or measures of Ia presynaptic inhibition. CONCLUSION: Resistance exercise in the presence of elevated fatigue and pain from a previous training session does not worsen recovery, or lead to significant alterations in quadriceps neuromuscular function. Reduction in muscle contractility, in the absence of declines in muscle activation, does not lead to decreased voluntary torque.

Declines in muscle contractility and activation during isometric contractions of the knee extensors vary with contraction intensity and exercise volume.

NEW FINDINGS: What is the central question of this study? Is there a critical threshold beyond which the loss of muscle contractility is regulated by the level of muscle activation during single-limb exercise of differing intensities and volumes? What is the main finding and its importance? Plateaus in the decline in muscle contractility during single-limb knee extension depended on both exercise volume and contraction intensity.  A plateau was only evident with an increase in exercise volume.  Muscle activation increased and did not decline despite substantial reductions in contractility. The findings indicate that the decrease in muscle contractility exhibited by resistance-trained men during the performance of submaximal isometric contractions with the knee extensors was not regulated by the level of muscle activation. ABSTRACT: Our study examined the influence of contraction intensity and exercise volume on changes in muscle contractility and activation of the knee extensor muscles. Maximal voluntary torque (MVT) and rate of change in torque, surface electromyograms, voluntary activation, V-waves and quadriceps resting twitch measures were assessed in 10 resistance-trained men during two experimental sessions. Each session began with an initial baseline series of contractions at a fixed intensity of 40% or 80% MVT. The 40%-only session continued with five contractions to task failure at 40% MVT. The 80% session continued with five contractions to failure each at 80%, 60% and 40% MVT. Greater reductions in MVT were observed during the baseline contractions of the 40%-only session compared with the 80% session at each matched-volume time point (P < 0.05), with similar changes in twitch values (P < 0.001). MVT and twitch values plateaued at each intensity during the 80% session and were significantly different across intensities: 80% > 60% > 40% (P < 0.001). There were no differences for measures during the five contractions at 40% MVT performed on the different days, despite a greater volume of exercise performed prior to the 40% MVT during the 80% session. At each contraction intensity, a plateau in contractility loss was observed as more contractions were performed. We found that initial increases in muscle activation were maintained in the presence of increases in exercise volume and, in contrast to the critical-threshold hypothesis, did not decline in parallel with reductions in muscle contractility.

Biomedical Beliefs Explain the Clinical Decisions Made by Exercise-Based Practitioners for People With Chronic Low Back Pain.

STUDY DESIGN: Cross-sectional survey. OBJECTIVE: This study surveyed the attitudes and beliefs of physiotherapists and accredited exercise physiologists (AEP) toward chronic low back pain (CLBP), in Australia. The objective of this study was to investigate the effect of biomedical and biopsychosocial attitudes and beliefs toward CLBP on clinical decision making in exercise-based practitioners. SUMMARY OF BACKGROUND DATA: The attitudes and beliefs of AEPs toward CLBP have not been studied. Literature regarding physiotherapists suggests a biomedical approach leading to more conservative treatment and on occasion, treatment going against practice guidelines. METHODS: Seventy five AEPs and 75 physiotherapists were surveyed using the pain attitudes and beliefs scale for physiotherapists, which consists of both a biomedical and biopsychosocial subscale. Clinical decision making was assessed using two patient vignettes. RESULTS: AEPs held higher biomedical beliefs compared with physiotherapists. No between-group differences were observed on the biopsychosocial subscale. Indeed, biomedical attitudes and beliefs did explain clinical decision making with higher scores reflecting a more conservative approach. However, biomedical beliefs influenced decision making regardless of profession. CONCLUSION: Biomedical attitudes and beliefs regarding CLBP influence clinical decision making in exercise-based practitioners, regardless of profession. AEPs reported higher biomedical scores, suggesting more frequent choice of conservative care. Thus, patients may receive inconsistent care and advice from practitioners within the same field. Based on clinical practice guidelines and the positive associations on clinical decision making of the biopsychosocial model, it is necessary to understand how best to provide exercise-based practitioners with education on how to apply a biopsychosocial approach to CLBP.Level of Evidence: 3.

The Role of Fear-Avoidance Beliefs on Low Back Pain-Related Disability in a Developing Socioeconomic and Conservative Culture: A Cross-Sectional Study of a Pakistani Population.

BACKGROUND: The relationship of low back pain, the world's top disabling condition, with functional disability is often explained by the mediation effect of fear, catastrophizing, and psychological distress. These relationships have not been explored within chronic back pain patients from a low socio-economic, predominantly Muslim country. Thus, it was unclear whether previously established pathways would be consistent in Pakistani pain patients to help guide Pakistani clinicians caring for back pain patients. This cross-sectional study translated English versions of questionnaires within the fear-avoidance model into Urdu, tested the clinimetric properties of the Urdu versions for people with chronic low back pain (CLBP) in Pakistan, and performed mediation analysis to investigate pathways of the fear-avoidance model. METHODS: Translation of questionnaires was completed in 4 steps using the forward-backward technique, with subsequent analyses for internal consistency (Cronbach's α), construct validity (Pearson's r-value), and test-retest reliability (ICC r-value). Multiple mediation analysis with bootstrapping was performed to analyze pathways within the fear-avoidance model from the Urdu translated questionnaires. RESULTS: A total of 151 people from Pakistan with CLBP completed the questionnaires, with good results for internal consistency (r > 0.85), convergent validity (r > 0.59), and test-retest reliability (ICC r > 0.85). The association of pain with disability was significant (B=2.36, r 2 = 0.19, p<0.001), and the indirect effect of the mediators explained 81% of pain intensity's total effect on disability. All mediators, apart from physical activity-related fear-avoidance beliefs, were significant mediators of the effect of pain intensity on disability. CONCLUSION: The Urdu versions of the fear-avoidance questionnaires show good clinimetric properties for use in clinical settings and research in Pakistan. These analyses support existing data for the mediation effect of catastrophizing, psychological distress, and self-efficacy on pain-related disability, and extends these findings to suggest that fear about work may be more important in a relatively lower socioeconomic sample of pain patients.

Changes in the quadriceps spinal reflex pathway after repeated sprint cycling are not influenced by ischemic preconditioning.

PURPOSE: We examined the effect of ischemic preconditioning (IPC) on changes in muscle force, activation, and the spinal reflex pathway during and after repeated sprint cycling. METHODS: Eight recreationally active men (high-intensity cardiorespiratory training > 3 times per week, > 6 months) completed two exercise sessions (5 sets of 5 cycling sprints, 150% max W), preceded by either IPC (3 × 5 min leg occlusions at 220 mmHg) or SHAM (3 × 5 min at 20 mmHg). Knee extensor maximal force and rate of force were measured before (PRE), immediately post (POST), 1H, and 24H after cycling. Twitch interpolation and resting potentiated twitches were applied to estimate voluntary activation and muscle contractility, respectively. Quadriceps H-reflex recruitment curves were collected at all time-points using 10 Hz doublet stimulation to allow estimation of H-reflex post-activation depression. Surface electromyograms and tissue oxygenation (via near-infrared spectroscopy) were continuously recorded during cycling. RESULTS: IPC did not affect any measure of neuromuscular function or performance during cycling. Maximal force and muscle contractility were significantly lower at POST and 1H compared to PRE and 24H by up to 50% (p < 0.01). Maximal force was lower than PRE at 24H by 8.7% (p = 0.028). Voluntary activation and rate of force were unchanged. A rightwards shift was observed for the H-reflex recruitment curve POST, and post-activation depression was higher than all other time-points at 24H (p < 0.05). Muscle activation and oxygenation decreased during cycling. CONCLUSIONS: IPC has a nominal effect on mechanisms associated with neuromuscular function during and after exercise in healthy populations.

Changes in Fatigue Are the Same for Trained Men and Women after Resistance Exercise.

PURPOSE: To measure changes in fatigue and knee-extensor torque in the 48 h after trained men and women completed a full-body resistance exercise session. METHODS: Eight trained women (mean ± SD: age, 25.6 ± 5.9 yr; height, 1.68 ± 0.06 m; mass, 71.0 ± 8.6 kg) and eight trained men (age, 25.5 ± 6.2 yr; height, 1.79 ± 0.05 m; mass, 86.4 ± 9.8 kg) performed a full-body resistance exercise session based on real-world athletic practice. Measurements were performed before and after the exercise session, as well as 1, 24, and 48 h after the session. Fatigue and pain were measured with standardized self-report measures. Maximal isometric contractions with the knee extensors and superimposed femoral nerve stimulation were performed to examine maximal torque, rate of torque development, voluntary activation, and muscle contractility. Two sets of 10 isokinetic contractions (60°·s) with the knee extensors were performed during the protocol with use of near-infrared spectroscopy to assess muscle oxygenation. EMG were recorded from two quadriceps muscles during all isometric and isokinetic contractions. RESULTS: Fatigue was increased from baseline for both sexes until 48 h after training (P < 0.001). Maximal torque and evoked twitch amplitudes were similarly reduced after exercise for men and women (P < 0.001). Voluntary activation and EMG amplitudes were unchanged after the training session. Muscle oxygenation was 13.3% ± 17.4% (P = 0.005) greater for women during the isokinetic repetitions, and the values were unchanged after the training session. CONCLUSIONS: This is the first study to show similar changes in the fatigue reported by trained men and women in the 48 h after a training session involving full-body resistance exercises. Sex differences in muscle oxygenation during exercise do not influence the reductions in muscle force, activation, or contractility after the training session.

The Effect of Resistance Training in Women on Dynamic Strength and Muscular Hypertrophy: A Systematic Review with Meta-analysis.

BACKGROUND: The effect of resistance training (RT) on adaptations in muscular strength and hypertrophy has never been examined in an exclusively female synthesis of the literature. OBJECTIVE: The objectives of this study were threefold: (1) to systematically review the literature on female adaptations to RT, characterising the effect in terms of muscular strength and hypertrophy; (2) to distinguish the individual effects of intervention duration, frequency, and intensity on these adaptations via sub-analysis; (3) to draw evidence-based conclusions regarding training expectations in female populations. METHODS: Three electronic databases were searched using terms related to RT combined with females or women. Random-effects meta-analyses were undertaken to estimate the effect of RT on muscular strength and hypertrophy in females. Possible predictors that may have influenced training-related effects (e.g., training intensity and volume) were explored using univariate analyses. RESULTS: The systematic search identified 14,067 articles of which a total of 24 studies met the inclusion criteria and were eligible. Upper body strength was assessed in 15 studies, lower body strength in 19 studies, and muscular hypertrophy in 15 studies. Study duration lasted between 4 weeks and 12 months. Large-effect sizes were found for upper body strength (Hedges' g = 1.70; p < 0.001) and lower body strength (Hedges' g = 1.40; p < 0.001). Following use of the Trim and Fill method (due to presence of publication bias), a large effect still remained for upper body strength (Hedges' g = 1.07), although a medium effect was found for lower body strength (Hedges' g = 0.52). A medium effect was found for muscular hypertrophy (g = 0.52, p = 0.002). Sub-analyses revealed that the moderating variables "training frequency" and "training volume" significantly influenced lower body muscular strength (p < 0.001). "Training frequency" and "sets per exercise" moderated the RT effects on upper body strength (p < 0.01). No moderating variables were found to significantly influence muscular hypertrophy. A trend for a moderating effect on upper body strength was found for "age of participants" (p = 0.08), whereby younger participants experienced a greater effect. A moderating effect was also observed where supervised training had a larger influence on the adaptation of lower body strength (p = 0.05) compared with unsupervised training. Methodological quality for the studies included in the review was found to be moderate. CONCLUSIONS: RT elicits large improvements in muscular strength and hypertrophy in healthy adult females. Training volume and frequency appear to be important variables that influence muscular strength.

Trained females exhibit less fatigability than trained males after a heavy knee extensor resistance exercise session.

PURPOSE: We examined differences between trained males and females in measures of muscular fatigability and central motor output after a resistance exercise session. METHODS: Sixteen trained males (n = 8) and females (n = 8) participated in the study. Knee extensor maximal torque and rate of torque development were measured before and after the exercise session, and the twitch interpolation technique was used during the maximal efforts to derive measures of voluntary activation and muscle contractility by supramaximal stimulation of the femoral nerve using 10 and 100 Hz doublets. Surface electromyograms were recorded during all maximal efforts to examine maximal and rate of quadriceps muscle activation. RESULTS: After exercise, maximal torque was reduced for both sexes by 26.3 ± 12.5% (p < 0.001). Absolute and relative vRTD was reduced only for males after exercise (p < 0.05). The early (0-50 ms) rate of muscle activation rise was similarly reduced for both sexes between 2.6 and 16.4% s-1 (p < 0.01), but males experienced an average decrease of 82.5 ± 72.1% s-1 for the maximal rate of muscle activation compared to no change for females (p = 0.02). Males had greater reductions (p < 0.05) for maximal twitch amplitudes and rate of twitch development (- 51.1 ± 21.5% and - 49.9 ± 22.8%, respectively) compared to females (- 35.8 ± 13.7% and - 31.5 ± 14.0%, respectively). CONCLUSIONS: These findings suggest that trained females are resistant to reductions in rapid torque development, despite similar reductions in maximal torque, after resistance exercise, with this result explained by better-maintained muscle contractility and maximal rate of muscle activation compared to males.

Changes in Unilateral Upper Limb Muscular Strength and Electromyographic Activity After a 16-Week Strength Training Intervention in Survivors of Breast Cancer.

Hagstrom, AD, Shorter, KA, and Marshall, PWM. Changes in unilateral upper limb muscular strength and Electroymographic activity after a 16-week strength training intervention in survivors of breast cancer. J Strength Cond Res 33(1): 225-233, 2019-Upper limb strength deficits are frequently observed following breast cancer (BC) and its treatments. It is currently unknown whether these unilateral deficits can be corrected by a standard bilateral strength training intervention. Twenty-three survivors of BC were included in this analysis. Fourteen performed a 16-week resistance training (RT) intervention, 9 were assigned to a usual care waitlist control group. Electromyographic analysis of the pectoralis major and triceps brachii were monitored during 3 maximal isometric contractions and a fatiguing endurance task. Muscular strength was significantly different between limbs at the start of the intervention (p = 0.02). Electromyographic amplitude and median frequency did not differ between limbs at the start of the intervention. Muscular strength was significantly different between limbs in the RT group at the end of the intervention (p = 0.01). Electromyographic amplitude did not differ between limbs or groups at the end of the intervention. Bilateral strength training did not correct the unilateral strength deficit observed in this group of survivors of breast cancer. Periods of unilateral strength training should be implemented into periodized RT programs in this cohort.

Anticipatory and compensatory postural adjustments in people with low back pain: a systematic review and meta-analysis.

BACKGROUND CONTEXT: Despite altered anticipatory (APAs) and compensatory postural adjustments (CPAs) being hypothesized to contribute to the onset and persistence of low back pain (LBP), results from studies comparing people with and without LBP are conflicting. PURPOSE: This systematic review aimed to determine whether APAs or CPAs are altered in the presence of acute and chronic LBP. STUDY DESIGN: A systematic review of studies was carried out. PATIENT SAMPLE: No patient sample was required. OUTCOME MEASURES: Between group standardized mean differences and 95% confidence intervals for APAs ad CPAs METHODS: A comprehensive search was conducted for articles comparing people with LBP (acute or chronic) to healthy controls for the onset or amplitude of muscle activity, center of pressure (COP), or kinematic responses to expected or unexpected perturbations. Two independent reviewers extracted data and assessed the methodological quality of relevant studies. Differences between people with and without LBP were calculated as standardized mean differences, and included in a meta-analysis if outcomes were homogeneous. Otherwise, a narrative synthesis was conducted. RESULTS: Twenty-seven studies were included, of which the majority examined muscle onsets in response to expected and unexpected perturbations. Only two studies compared people with and without acute LBP, and results for these studies were conflicting. The results show delayed muscle onsets in response to expected and unexpected perturbations for people with chronic LBP when compared with healthy controls. No conclusive evidence for differences between people with and without chronic LBP for COP or kinematic responses. CONCLUSIONS: There is currently no convincing evidence of differences between people with and without acute LBP for APAs or CPAs. Conversely, delayed muscle onsets in people with chronic LBP suggest APAs and CPAs are altered in this population. However, the functional relevance of these delayed muscle onsets (eg, COP and kinematics) is unknown.

Acute attenuation of fatigue after sodium bicarbonate supplementation does not manifest into greater training adaptations after 10-weeks of resistance training exercise.

PURPOSE: In two concurrent studies, we aimed to a) confirm the acute effect of 0.3 g·kg-1 body weight (BW) sodium bicarbonate (NaHCO3) supplementation on central and peripheral mechanisms associated with explosive power (Study 1) and b) determine whether chronic NaHCO3 supplementation would improve the adaptive response of the neuromuscular system during a 10-week resistance training program (Study 2). METHODS: Eight resistance trained participants volunteered after providing written consent. The experimental design consisted of a week of baseline testing, followed by ten weeks of training with progress measures performed in Week 5. Study 1 involved neuromuscular measurements before and after the leg extension portion of a power based training session performed in Week 1. Changes in maximal torque (MVT) and rates of torque development (RTD), along with other variables derived from femoral nerve stimulation (e.g. voluntary activation, neural recruitment) were analysed to determine the extent of fatigue under NaHCO3 or placebo conditions. Changes in these same variables, coupled with functional 1-repetition maximum leg extension strength, were measured in Study 2 from baseline (Week 0) to Week 5, and again at Week 10. RESULTS AND CONCLUSION: In Study 1, we observed a decline after the leg extension task in both MVT (~ 30%) and rates of torque production (RTD) irrespective of acid-base status, however the decline in maximal RTD (RTDMAX) was nearly 20% less in the NaHCO3 condition when compared to placebo (mean difference of 294.8 ± 133.4 Nm·s-1 (95% CI -583.1 to -6.5 Nm, p < 0.05)). The primary finding in Study 2, however, suggests that introducing NaHCO3 repeatedly during a 10-week RT program does not confer any additional benefit to the mechanisms (and subsequent adaptive processes) related to explosive power production.