Ross A. Clark

The Acute Effects of a Single Set of Contrast Preloading on a Loaded Countermovement Jump Training Session

The aim of this research was to assess the effect of a single set of contrast preloading on peak vertical displacement (PD) during a loaded countermovement jump (LCMJ) training session. Nine strength-trained males participated in 2 randomly assigned, crossover design testing sessions consisting of 5 sets of 6 repetitions of 20-kg LCMJs with 3-minute rest intervals between sets. The preloading intervention was performed 3 minutes after the first set and 4 minutes before the second set of 20-kg LCMJs. The control (CON) group performed 1 set of 20-kg LCMJs, whereas the jump squat (JS) group performed 1 set of 40-kg LCMJs. The number of repetitions performed during each preloading condition was varied to match total concentric work between the 2 sessions. A significant (p < 0.05) preload 3 set interaction for PD was observed, with the JS group jumping significantly higher during the third set performed after the preload in comparison with the CON group. Analysis of peak power output and mean power output during the concentric movement for this set revealed that as the knee flexion angle increased, the effect of the preload was augmented. These results suggest that a single set of preloading exercises enhances performance during a lower-body explosive power training session; however, the effects of a single preloading set may not peak until midway through the training session.

Neuromuscular deficits following peripheral joint injury: A neurophysiological hypothesis

In addition to biomechanical disturbances, peripheral joint injuries (PJIs) can also result in chronic neuromuscular alterations due in part to loss of mechanoreceptor‐mediated afferent feedback. An emerging perspective is that PJI should be viewed as a neurophysiological dysfunction, not simply a local injury. Neurophysiological and neuroimaging studies have provided some evidence for central nervous system (CNS) reorganization at both the cortical and spinal levels after PJI. The novel hypothesis proposed is that CNS reorganization is the underlying mechanism for persisting neuromuscular deficits after injury, particularly muscle weakness. There is a lack of direct evidence to support this hypothesis, but future studies utilizing force‐matching tasks with superimposed transcranial magnetic stimulation may be help clarify this notion. Muscle Nerve 51: 327–332, 2015

Between-leg differences in challenging single-limb balance performance one year following anterior cruciate ligament reconstruction

Following anterior cruciate ligament (ACL) rupture, reconstructive surgery (ALCR) is often performed to mechanically stabilise the knee, however functional deficits often persist long after surgery. Impaired single-limb standing balance has been observed in the ACLR limb compared to healthy individuals. However, it remains inconclusive as to whether these same balance deficits exist between the injured and contralateral uninjured limbs, during challenging balance tasks, and at a time when patients are permitted to return to sport. 100 adults who had undergone a primary hamstring-tendon ACLR 12 months previously (68 male; median[IQR] age: 28.1[14.1] years) performed tests of single-limb standing with the knee in a functional position of 20-30° flexion, with their eyes closed, over 20s (Nintendo Wii Balance Board). Two repetitions were performed on the ACLR and uninjured limb. Measures of postural control included centre of pressure (CoP) path velocity, anterior-posterior and mediolateral range and standard deviation, and were averaged across the two trials. Wilcoxon signed-rank tests showed no significant between-leg differences in single-limb balance for any of the CoP measures of interest (all P values>0.686). Further, multiple linear regression analyses showed no significant associations between concomitant meniscectomy or chondral lesions noted at the time of ACLR and measures of single-limb balance on the ACLR limb one year later (all P values>0.213). In the context of prior research, these findings suggest bilateral balance deficits may exist prior to ACL injury, or appear post ACL-injury or ACLR. Treatment of balance deficits should therefore consider both limbs after ACLR.

Reliability and validity of the Wii Balance Board for assessment of standing balance: A systematic review

The use of force platform technologies to assess standing balance is common across a range of clinical areas. Numerous researchers have evaluated the low-cost Wii Balance Board (WBB) for its utility in assessing balance, with variable findings. This review aimed to systematically evaluate the reliability and concurrent validity of the WBB for assessment of static standing balance. Articles were retrieved from six databases (Medline, SCOPUS, EMBASE, CINAHL, Web of Science, Inspec) from 2007 to 2017. After independent screening by two reviewers, 25 articles were included. Two reviewers performed the data extraction and quality assessment. Test-retest reliability was investigated in 12 studies, with intraclass correlation coefficients or Pearsons correlation values showing a range from poor to excellent reliability (range: 0.27 to 0.99). Concurrent validity (i.e. comparison with another force platform) was examined in 21 studies, and was generally found to be excellent in studies examining the association between the same outcome measures collected on both devices. For studies reporting predominantly poor to moderate validity, potentially influential factors included the choice of 1) criterion reference (e.g. not a common force platform), 2) test duration (e.g. <30 s for double leg), 3) outcome measure (e.g. comparing a centre of pressure variable from the WBB with a summary score from the force platform), 4) data acquisition platform (studies using Apple iOS reported predominantly moderate validity), and 5) low sample size. In conclusion, evidence suggests that the WBB can be used as a reliable and valid tool for assessing standing balance. Protocol registration number: PROSPERO 2017: CRD42017058122.

Standing balance and inter-limb balance asymmetry at one year post primary anterior cruciate ligament reconstruction: Sex differences in a cohort study of 414 patients

BACKGROUND Static standing balance can be safely assessed early following anterior cruciate ligament reconstruction (ACLR), and deficits may have important implications for long-term outcomes. This study includes a large cohort of people post-ACLR and has the primary aim of establishing whether inter-limb and sex differences exist, with a secondary aim of assessing the association between static balance variables and other outcome measures. METHODS A total of 414 patients with a primary ACLR performed a 30-s static single leg balance test. Centre of pressure (COP) path length, antero-posterior (AP) and medio-lateral (ML) sway range and slow and fast speed COP path-length were examined. Additional measures included single and triple hop distance and symmetry, knee flexion range of motion, ligament laxity and the International Knee Documentation Committee (IKDC) subjective knee evaluation form. RESULTS No significant inter-limb balance differences were present in females. Significant, yet small to negligible effect size (ES) differences were present in males for ML range (ES=0.19), and AP and ML axis slow speed path length (ES=0.11 and 0.23 respectively). Significant, negligible to moderate effect size (ES range=<0.01 to 0.60) sex differences were observed, with females showing reduced sway compared to males. No balance variables had associations with any other variable that were greater than weak. DISCUSSION Our findings provide evidence that primary ACLR does not appear to negatively impact single leg standing balance on the operated limb more than the non-operated side. The lack of association with other outcome measures warrants further longitudinal examination into the utility of static standing balance assessment.

Lumbar extensor muscle force control is associated with disability in people with chronic low back pain

Background The ability to control lumbar extensor force output is necessary for daily activities. However, it is unknown whether this ability is impaired in chronic low back pain patients. Similarly, it is unknown whether lumbar extensor force control is related to the disability levels of chronic low back pain patients. Methods Thirty‐three chronic low back pain and 20 healthy people performed lumbar extension force‐matching task where they increased and decreased their force output to match a variable target force within 20%–50% maximal voluntary isometric contraction. Force control was quantified as the root‐mean‐square‐error between participants’ force output and target force across the entire, during the increasing and decreasing portions of the force curve. Within‐ and between‐group differences in force‐matching error and the relationship between back pain groups force‐matching results and their Oswestry Disability Index scores were assessed using ANCOVA and linear regression respectively. Findings Back pain group demonstrated more overall force‐matching error (mean difference = 1.60 [0.78, 2.43], P < 0.01) and more force‐matching error while increasing force output (mean difference = 2.19 [1.01, 3.37], P < 0.01) than control group. The back pain group demonstrated more force‐matching error while increasing than decreasing force output (mean difference = 1.74, P < 0.001, 95%CI [0.87, 2.61]). A unit increase in force‐matching error while decreasing force output is associated with a 47% increase in Oswestry score in back pain group (R2 = 0.19, P = 0.006). Interpretation Lumbar extensor muscle force control is compromised in chronic low back pain patients. Force‐matching error predicts disability, confirming the validity of our force control protocol for chronic low back pain patients. HighlightsLumbar extensor muscle force control is impaired in people with chronic low back pain.The ability to accurately increase, but not decrease, force output is impaired in people with chronic low back pain.Impairment in lumbar extensor muscle force control is associated with disability in people with chronic low back pain.

Do clinical tests of spasticity accurately reflect muscle function during walking: A systematic review

ABSTRACT Objective: The aim of this systematic review was to establish the ecological validity of clinical tests of lower limb spasticity by determining whether the range of motion (ROM) and speed of limb movement during the assessment accurately replicate muscle function and joint biomechanics during walking. Methods: An electronic search of ten databases was performed to identify all relevant articles. The reference lists of all included articles were also searched. Identification of relevant articles, data extraction and quality assessment were performed independently by two reviewers. Results: Seventeen studies were included in the review. The Modified Ashworth Scale was the most commonly used clinical measure of lower limb spasticity. The ROM and speed of assessment were poorly reported for clinical scales of lower limb spasticity, making it difficult to draw conclusions regarding the relevance of these scales to walking performance. Conclusions: The ecological validity of the clinical scales of spasticity could not be determined as studies did not adequately report their testing procedure. Further research into the ecological validity of clinical scales of spasticity is required in order to better understand the impact that spasticity has on functional activities such as walking.

Three-dimensional assessment of squats and drop jumps using the Microsoft Xbox One Kinect: Reliability and validity

ABSTRACT The Microsoft Xbox One Kinect™ (Kinect V2) contains a depth camera that can be used to manually identify anatomical landmark positions in three-dimensions independent of the standard skeletal tracking, and therefore has potential for low-cost, time-efficient three-dimensional movement analysis (3DMA). This study examined inter-session reliability and concurrent validity of the Kinect V2 for the assessment of coronal and sagittal plane kinematics for the trunk, hip and knee during single leg squats (SLS) and drop vertical jumps (DVJ). Thirty young, healthy participants (age = 23 ± 5yrs, male/female = 15/15) performed a SLS and DVJ protocol that was recorded concurrently by the Kinect V2 and 3DMA during two sessions, one week apart. The Kinect V2 demonstrated good to excellent reliability for all SLS and DVJ variables (ICC ≥ 0.73). Concurrent validity ranged from poor to excellent (ICC = 0.02 to 0.98) during the SLS task, although trunk, hip and knee flexion and two-dimensional measures of knee abduction and frontal plane projection angle all demonstrated good to excellent validity (ICC ≥ 0.80). Concurrent validity for the DVJ task was typically worse, with only two variables exceeding ICC = 0.75 (trunk and hip flexion). These findings indicate that the Kinect V2 may have potential for large-scale screening for ACL injury risk, however future prospective research is required.

Exercise Interventions for the Prevention and Treatment of Groin Pain and Injury in Athletes: A Critical and Systematic Review

BackgroundGroin injury is a common musculoskeletal complaint for athletes competing in a variety of sports. The extent to which exercise interventions incorporating external load are an appropriate option for the treatment and prevention of groin injury in athletes is not yet clear.ObjectivesThe aim of this review was to describe and evaluate exercise therapy interventions and outcomes for the treatment and prevention of groin injury with specific attention to application of external load.Data SourcesThe databases Medline, PubMed, SPORTDiscus, Web of Science, and Cochrane were searched on 18 April 2016.Study Eligibility CriteriaThis review was registered as PROSPERO CRD42016037752 and a systematic search was conducted with the following inclusion criteria: any study design evaluating exercise interventions for the prevention or treatment of groin pain in athletes.Data AnalysisTwo independent authors screened search results, performed data extraction, assessed risk of bias using the modified Downs and Black appraisal tool and determined strength and level of evidence. Reporting standards for exercise interventions were assessed using the Consensus for Exercise Reporting Template (CERT).ResultsA total of 1320 titles were identified with 14 studies satisfying the inclusion criteria, four (29%) of which demonstrated low risk of bias. Ten (71%) studies utilised external load as a component of the exercise intervention. Reporting standards for exercise intervention scores ranged from 0 to 63%.ConclusionThere is limited evidence from level 2 and 3 studies indicating exercise therapy may reduce the incidence and hazard risk of sustaining a groin injury in athletes. There is strong evidence from level 4 studies indicating exercise therapy is beneficial as a treatment for groin injury in athletes in terms of symptom remission, return to sport and recurrence outcomes. However, there are limited studies with low risk of bias, and exercise interventions for the treatment of groin injury are poorly described.

Benefits of home-based multidisciplinary exercise and supportive care in inoperable non-small cell lung cancer – protocol for a phase II randomised controlled trial

BackgroundLung cancer is one of the most commonly diagnosed cancers, and is a leading cause of cancer mortality world-wide. Due to lack of early specific symptoms, the majority of patients present with advanced, inoperable disease and five-year relative survival across all stages of non-small cell lung cancer (NSCLC) is 14%. People with lung cancer also report higher levels of symptom distress than those with other forms of cancer. Several benefits for survival and patient reported outcomes are reported from physical activity and exercise in other tumour groups. We report the protocol for a study investigating the benefits of exercise, behaviour change and symptom self-management for patients with recently diagnosed, inoperable, NSCLC.MethodsThis multi-site, parallel-group, assessor-blinded randomised controlled trial, powered for superiority, aims to assess functional and patient-reported outcomes of a multi-disciplinary, home-based exercise and supportive care program for people commencing treatment. Ninety-two participants are being recruited from three tertiary-care hospitals in Melbourne, Australia. Following baseline testing, participants are randomised using concealed allocation, to receive either: a) 8 weeks of home-based exercise (comprising an individualised endurance and resistance exercise program and behaviour change coaching) and nurse-delivered symptom self-management intervention or b) usual care. The primary outcome is the between-group difference in the change in functional exercise capacity (six-minute walk distance) from baseline to post-program assessment. Secondary outcomes include: objective and self-reported physical activity levels, physical activity self-efficacy, behavioural regulation of motivation to exercise and resilience, muscle strength (quadriceps and grip), health-related quality of life, anxiety and depression and symptom interference.DiscussionThere is a lack of evidence regarding the benefit of exercise intervention for people with NSCLC, particularly in those with inoperable disease receiving treatment. This trial will contribute to evidence currently being generated in national and international trials by implementing and evaluating a home-based program including three components not yet combined in previous research, for people with inoperable NSCLC receiving active treatment and involving longer-term follow-up of outcomes. This trial is ongoing and currently recruiting.Trial registrationThis trial was prospectively registered on the Australian New Zealand Clinical Trials Registry (ACTRN12614001268639: (4/12/14).