Acute changes in kinematic and muscle activity patterns in habitually shod rearfoot strikers while running barefoot

The aim of this study was to observe changes in the kinematics and muscle activities when barefoot running was initially adopted by six habitually shod, recreational rearfoot striking runners. Participants ran on a treadmill shod for 5 min, completed 3 × 10-min intervals of barefoot running and then completed a final minute of shod running at a self-selected pace. Dependent variables (speed, joint angles at foot-contact, joint range of motion (ROM), mean and peak electromyography (EMG) activity) were compared across conditions using repeated measures ANOVAs. Anterior pelvic tilt and hip flexion significantly decreased during barefoot conditions at foot contact. The ROM for the trunk, pelvis, knee and ankle angles decreased during the barefoot conditions. Mean EMG activity was reduced for biceps femoris, gastrocnemius lateralis and tibialis anterior during barefoot running. The peak activity across the running cycle decreased in biceps femoris, vastus medialis, gastrocnemius medialis and tibialis anterior during barefoot running. During barefoot running, tibialis anterior activity significantly decreased during the pre-activation and initial contact phases; gastrocnemius lateralis and medialis activity significantly decreased during the push-off phase. Barefoot running caused immediate biomechanical and neuromuscular adaptations at the hip and pelvis, which persisted when the runners donned their shoes, indicating that some learning had occurred during an initial short bout of barefoot running

Systematic nonlinear relations between displacement amplitude and joint mechanics at the human wrist

This study quantified the systematic effects on wrist joint mechanics of changes in amplitude of displacement ranging from within the region of short range stiffness (0.2% of resting muscle length) up to 3% of resting muscle length. The joint mechanics were modelled using a second order system from which estimates of joint stiffness, viscosity, inertia, natural resonant frequency and damping ratio were obtained. With increasing amplitude of displacement, the stiffness decreased by 31%, the viscosity decreased by 73%, the damping ratio decreased by 71% and the resonant frequency decreased from 10.5 Hz to 7.3 Hz. The patterns of change in joint mechanics with displacement amplitude were nonlinear but systematic and were well described by power relationships with high R2 values. These relationships provide normative data for the adult population and may be used in the modelling of human movement, in the study of neurological disorders and in robotics where human movement is simulated. The observed patterns of high initial stiffness and viscosity, decreasing progressively as displacement amplitude increases, may provide a good compromise between postural stability and liveliness of voluntary movement

The facilitators and barriers to exercise in the Noongar Aboriginal population in Perth, Australia

Indigenous Standpoint Theory forms the epistemological foundation for this study and methodological choices were made within this theoretical framework to ensure culturally responsive research processes that engaged the Indigenous agenda of self-determination and rights. The objectives of this research were to determine: (i) Indigenous perceptions of the facilitators and barriers to exercise; (ii) The potential feasibility and sustainability of an exercise intervention. In this context, Participatory Action Research methods were used to design the data-gathering instrument for the study—a questionnaire, co-designed with the Noongar Aboriginal community of Perth, Western Australia. This self-administered questionnaire, distributed to participants by email, post and manual delivery, sought to elicit the factors that impact uptake and retention of regular exercise activities. Questionnaire data included individual demographic detail and specific question responses on labelled 5 point Likert Scales. Specific question responses were tabulated by Likert Scale label category and the response distribution for each question was enumerated. Simple descriptive statistics (measures of central tendency and variance) were used to characterize the data set and the Chi squared test was used to evaluate frequency differences between males and females. A total of 133 participants (71 females) completed the questionnaire. The results indicated that people valued exercise. The most common barriers indicated by participants were exercising with an injury (63%), changing diet (58%), finding time to exercise every day (55%) and exercising the next day with pain from exercising the day before (54%). A larger proportion of males (34%) than females (24%) reported greater ease in finding time to exercise every day (p \u3c 0.05). Facilitators mainly related to the potential social and community benefits of exercising with other people, preferably in small groups, and the importance of a culturally secure venue. These findings shed light on what a culturally secure exercise programme might involve for the Noongar community. As this may have implications for other Aboriginal and Torres Strait Islander and international First Nations’ Peoples, more focused research is needed on the place of traditional physical activities and the nature of culturally secure exercise programmes and spaces to enable wider application

Evidence of viscerally-mediated cold-defence thermoeffector responses in man

Sudomotor activity is modified by both warm and cold fluid ingestion during heat stress, independently of differences in core and skin temperatures, suggesting independent viscerally-mediated modification of thermoeffectors. The purpose of the present study was to determine whether visceral thermoreceptors modify shivering responses to cold stress. Ten males (27 ± 5y, 1.73 ± 0.06 m, 78.4 ± 10.7 kg) underwent whole-body cooling via 5 °C water perfusion-suit, on four occasions, to induce a steady-state shivering response, at which point two aliquots of 1.5 ml/kg (SML) and 3.0 ml/kg (LRG), separated by 20- min, of either 7°C, 22°C, 37°C or 52°C water were ingested. Rectal, mean skin and mean body temperature (Tb), electromyographic activity (EMG), metabolic rate (M) and whole-body thermal sensation on a visual analogue scale (WBTS) ranging from 0 mm [very cold] to 200 mm [very hot] were all measured throughout. Tb was not different between all fluid temperatures following SML (7°C:35.7 ± 0.5°C, 22°C:35.6 ± 0.5°C, 37°C:35.5 ± 0.4°C, 52°C:35.5 ± 0.4°C; P = 0.27) or LRG (7°C:35.3 ± 0.6°C, 22°C:35.3 ± 0.5°C, 37°C:35.2 ± 0.5°C, 52°C:35.3 ± 0.5°C; P = 0.99) fluid ingestion. With SML ingestion, greater metabolic rate and cooler thermal sensations were observed with 7°C (M:179 ± 55 W, WBTS:29 ± 21 mm) compared to 52°C (M:164 ± 34 W, WBTS:51 ± 28 mm; all P < 0.05) ingestion. With LRG ingestion, compared to shivering and thermal sensations with 37 °C ingestion (M:215 ± 47 W, EMG:3.9 ± 2.5%MVC, WBTS:33 ± 2 mm) values were different (all P < 0.05) following 7°C (M:269 ± 77 W, EMG:5.5 ± 0.9%MVC, WBTS:14 ± 12 mm), 22°C (M:270 ± 86 W, EMG:5.6 ± 1.0%MVC, WBTS:18 ± 19 mm) and 52°C (M:179 ± 34 W, EMG:3.3 ± 2.1%MVC, WBTS:53 ± 28 mm) ingestion. In conclusion, ingesting 52°C fluids decreased shivering and the sensation of coolness, whereas 22°C and 7°C fluids increased shivering and sensations of coolness to similar levels, independently of core and skin temperature

Maturation-based Corrective Adjustment Procedures (Mat-CAPs) in youth swimming: Evidence for restricted age-group application in females.

Inter-individual differences in maturation-associated development can lead to variations in physical performance, resulting in performance (dis)advantages and maturation selection bias within youth sport systems. To address such bias and account for maturational differences, Maturation-based Corrective Adjustment Procedures (Mat-CAPs) could be beneficial. The present study aimed to: (1) determine maturity timing distributions in youth female swimming; (2) quantify the relationship between maturation status and 100-m front-crawl (FC) performance; (3) implement Mat-CAPs to remove maturational influences upon swimming performance. For Aim 1 and 2, participants were 663 female (10–15 years) swimmers who participated in 100-m FC events at Australian regional, state, and national-level competitions between 2016–2020 and underwent anthropometric assessment (mass, height and sitting height) to estimate maturity timing and offset. For Aim 3, participants aged 10–13 years were categorised into maturity timing categories. Maturity timing distributions for Raw (‘All’, ‘Top 50%’ and ‘Top 25%’) and Correctively Adjusted swim times were examined. Chi-square, Cramer’s V and Odds Ratios determined the presence of maturation biases, while Mat-CAPs identified whether such biases were removed in targeted age and selection-groups. Results identified that between 10–13 years, a significantly higher frequency of ‘early’ maturers was apparent, although tapered toward higher frequencies of ‘Late-normative’ maturers by 14–15 years. A curvilinear relationship between maturity-offset and swim performance was identified (R2 = 0.51, p<0.001) and utilised for Mat-CAPs. Following Mat-CAPs application, maturity timing biases evident in affected age-groups (10–13 years), and which were magnified at higher selection levels (‘Top 50%’ & ‘25%’ of swim performances) were predominantly removed. Findings highlight how maturation advantages in females occurred until approximately 13 years old, warranting restricted Mat-CAPs application. Mat-CAPS has the potential to improve female swimmer participation experiences and evaluation

Role of the kinetic chain in shoulder rehabilitation: Does incorporating the trunk and lower limb into shoulder exercise regimes influence shoulder muscle recruitment patterns? Systematic review of electromyography studies

Objective To investigate the influence of trunk and lower limb motion on electromyography (EMG) muscle activity and recruitment patterns around the shoulder. Design Systematic review. Data sources MEDLINE, CINAHL, PEDro, AMED, PubMed, Cochrane Central Register of Controlled trials, Cochrane Database of Systematic reviews, SportsDiscuss and PROSPERO. Eligibility criteria Studies investigating both multiregional kinetic chain (KC) shoulder exercises and localised non-kinetic chain (nKC) shoulder exercises in healthy subjects under the same experimental conditions were included in this review. Results KC exercises produced greater EMG activation levels in 5 of 11 studies for the lower trapezius. Of the remaining studies, five found no difference between the exercise types and one favoured nKC exercises. KC exercises produced greater EMG activation levels in 5 of 11 studies for the serratus anterior. Of the remaining studies, three reported the opposite and three found no significant difference between the exercise types. nKC exercises produced greater EMG activation in infraspinatus in three of four studies. KC exercises produced the lowest trapezius muscle ratios in all studies. Studies investigating the upper trapezius, middle trapezius, supraspinatus, subscapularis, biceps brachii, latifissimus dorsi, pectoralis major, deltoid, and trapezius and serratus anterior ratios showed inconsistency. Conclusion This review found evidence that integrating the KC during shoulder rehabilitation may increase axioscapular muscle recruitment, produce lower trapezius muscle ratios and reduce the demands on the rotator cuff. Stepping appears preferable to squatting. PROSPERO registration number CRD42015032557, 2015. © Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ

Role of the kinetic chain in shoulder rehabilitation: does incorporating the trunk and lower limb into shoulder exercise regimes influence shoulder muscle recruitment patterns? Systematic review of electromyography studies

Objective: To investigate the influence of trunk and lower limb motion on electromyography (EMG) muscle activity and recruitment patterns around the shoulder. Design: Systematic review. Data sources: MEDLINE, CINAHL, PEDro, AMED, PubMed, Cochrane Central Register of Controlled trials, Cochrane Database of Systematic reviews, SportsDiscuss and PROSPERO. Eligibility: criteria Studies investigating both multiregional kinetic chain (KC) shoulder exercises and localised non-kinetic chain (nKC) shoulder exercises in healthy subjects under the same experimental conditions were included in this review. Results: KC exercises produced greater EMG activation levels in 5 of 11 studies for the lower trapezius. Of the remaining studies, five found no difference between the exercise types and one favoured nKC exercises. KC exercises produced greater EMG activation levels in 5 of 11 studies for the serratus anterior. Of the remaining studies, three reported the opposite and three found no significant difference between the exercise types. nKC exercises produced greater EMG activation in infraspinatus in three of four studies. KC exercises produced the lowest trapezius muscle ratios in all studies. Studies investigating the upper trapezius, middle trapezius, supraspinatus, subscapularis, biceps brachii, latifissimus dorsi, pectoralis major, deltoid, and trapezius and serratus anterior ratios showed inconsistency. Conclusion: This review found evidence that integrating the KC during shoulder rehabilitation may increase axioscapular muscle recruitment, produce lower trapezius muscle ratios and reduce the demands on the rotator cuff. Stepping appears preferable to squatting

An Investigation of Compensation and Adaptation to Auditory Perturbations in Individuals With Acquired Apraxia of Speech

Two auditory perturbation experiments were used to investigate the integrity of neural circuits responsible for speech sensorimotor adaptation in acquired apraxia of speech (AOS). This has implications for understanding the nature of AOS as well as normal speech motor control. Two experiments were conducted. In Experiment 1, compensatory responses to unpredictable fundamental frequency (F0) perturbations during vocalization were investigated in healthy older adults and adults with acquired AOS plus aphasia. F0 perturbation involved upward and downward 100-cent shifts versus no shift, in equal proportion, during 2 s vocalizations of the vowel /a/. In Experiment 2, adaptive responses to sustained first formant (F1) perturbations during speech were investigated in healthy older adults, adults with AOS and adults with aphasia only (APH). The F1 protocol involved production of the vowel /ε/ in four consonant-vowel words of Australian English (pear, bear, care, dare), and one control word with a different vowel (paw). An unperturbed Baseline phase was followed by a gradual Ramp to a 30% upward F1 shift stimulating a compensatory response, a Hold phase where the perturbation was repeatedly presented with alternating blocks of masking trials to probe adaptation, and an End phase with masking trials only to measure persistence of any adaptation. AOS participants showed normal compensation to unexpected F0 perturbations, indicating that auditory feedback control of low-level, non-segmental parameters is intact. Furthermore, individuals with AOS displayed an adaptive response to sustained F1 perturbations, but age-matched controls and APH participants did not. These findings suggest that older healthy adults may have less plastic motor programs that resist modification based on sensory feedback, whereas individuals with AOS have less well-established and more malleable motor programs due to damage from stroke