Reflex inhibition of the human quadriceps in the presence of knee joint damage

Quadriceps weakness can occur by atrophy and by reflex inhibition due to stimuli from a damaged knee joint. The mechanisms by which quadriceps weakness occurs are not understood enough to allow weakness to be prevented. The nature of reflex inhibition has been studied in patients undergoing arthrotomy and meniscectomy in order to find ways of preventing inhibition. The maximal voluntary activation (MVA) of quadriceps was recorded, using surface integrated electromyography, during straight leg isometric contractions before end after surgery. Post-operative inhibition was expressed as the percentage reduction from the pre-operative MVA. Knee pain experienced during each contraction was recorded on a linear analogue scale. Post-meniscectomy reflex inhibition of quadriceps is severe (70-80% during the first 3 days), prolonged (35-40% at 2 weeks) and is not related to pain after 24 hours. Inhibition can be temporarily prevented by per-operative infiltration of the knee with a local anaesthetic (Chapter 3). Prolonged voluntary tourniquet ischaemia in normal subjects did not alter subsequent quadriceps function, indicating that the reduced NVA observed in the meniscectomy patients was not due to ischaemia (Chapter 4). Isometric quadriceps contractions are inhibited less with the knee flexed than extended (Chapter 5). Transcutaneous nerve stimulation (TNS) had only a small effect on inhibition, and pain relief was similar in both the treatment and the control groups (Chapter 6). In patients who developed knee joint effusions post-operatively, aspiration always reduced inhibition but did not abolish it (Chapter 7). The effect of knee joint afferent activity on quadriceps activation was studied in normal subjects with knee joint infusions. Intra-articular pressure/volume relationships at rest were similar to results reported by other authors, and during contraction the pressures were higher at each volume (Chapter 8). Inhibition of reflex activation of quadriceps was examined by measuring quadriceps H-reflex (Chapters 9,10 and 11). The central neural pathway of the joint afferent stimuli was investigated by testing for spatial facilitation between joint stimulation (by infusion) and known pathways of quadriceps H-reflex inhibition (by stimulating various nerves). The results suggest that the joint afferents have connections with Ib and cutaneous flexor reflex afferent (FRA) inhibitory pathways, but results for reciprocal inhibition were equivocal. The present investigations have quantified the severity and duration of post-meniscectomy quadriceps inhibition, and have confirmed that the inhibition occurs by a reflex mechanism originating from the knee joint and that it is possible to block the inhibitory stimuli. Investigation of the pathway of the afferent stimuli suggested convergence of joint afferents with Ib pathways and with cutaneous FRA pathways

On the existence of combinatorial configurations

A (v, b, r, k) combinatorial configuration can be defined as a connected, (r, k)-biregular bipartite graph with v vertices on one side and b vertices on the other and with no cycle of length 4. Combinatorial configurations have become very important for some cryptographic applications to sensor networks and to peer-to-peer communities. Configurable tuples are those tuples (v, b, r, k) for which a (v, b, r, k) combinatorial configuration exists. It is proved in this work that the set of configurable tuples with fixed r and k has the structure of a numerical semigroup. The semigroup is completely described whenever r = 2 or r = 3. For the remaining cases some bounds are given on the multiplicity and the conductor of the numerical semigroup. This leads to some concluding results on the existence of configurable tuples.Peer Reviewe

Terrestrial neuro-musculoskeletal rehabilitation and astronaut reconditioning : Reciprocal knowledge transfer [Editorial]

[Extract] Research on astronauts can benefit patients with conditions affecting the neuro-musculoskeletal systems and vice versa, as both face the challenge of managing the effects of disuse. Deconditioning in astronauts after spaceflight is a useful model for studying interventions for optimal recovery, as changes occur relatively rapidly and without the complication of underlying pathology seen in musculoskeletal and neurological disorders, where the effects of disuse are difficult to study in isolation. Physical inactivity is a major problem in the general population, despite well-known benefits, causing public health and economic concerns worldwide (Kohl et al., 2012, Lee et al., 2012), so translating motivation strategies from astronauts would be very beneficial. Clinical conditions associated with disuse can also provide lessons for optimising exercise programmes to minimise deconditioning during spaceflight and reconditioning the astronaut on their return to Earth. The purpose of this Supplement is to highlight areas where space and terrestrial research and clinical management may have lessons for one another

Mechanisms of pelvic floor muscle function and the effect on the urethra during a cough

Background: Current measurement tools have difficulty identifying the automaticphysiologic processes maintaining continence, and many questions still remainabout pelvic floor muscle (PFM) function during automatic events.Objective: To perform a feasibility study to characterise the displacement, velocity,and acceleration of the PFM and the urethra during a cough.Design, setting, and participants: A volunteer convenience sample of 23 continentwomen and 9 women with stress urinary incontinence (SUI) from the generalcommunity of San Francisco Bay Area was studied.Measurements: Methods included perineal ultrasound imaging, motion trackingof the urogenital structures, and digital vaginal examination. Statistical analysisused one-tailed unpaired student t tests, and Welch’s correction was applied whenvariances were unequal.Results and limitations: The cough reflex activated the PFM of continent women tocompress the urogenital structures towards the pubic symphysis, which wasabsent in women with SUI. The maximum accelerations that acted on the PFMduring a cough were generally more similar than the velocities and displacements.The urethras of women with SUI were exposed to uncontrolled transverse accelerationand were displaced more than twice as far ( p = 0.0002), with almost twicethe velocity ( p = 0.0015) of the urethras of continent women. Caution regardingthe generalisability of this study is warranted due to the small number of women inthe SUI group and the significant difference in parity between groups.Conclusions: During a cough, normal PFM function produces timely compressionof the pelvic floor and additional external support to the urethra, reducing displacement,velocity, and acceleration. In women with SUI, who have weakerurethral attachments, this shortening contraction does not occur; consequently,the urethras of women with SUI move further and faster for a longer duratio

Measurement of ageing effects on muscle tone and mechanical properties of rectus femoris and biceps brachii in healthy males and females using a novel hand-held myometric device

BackgroundAge and gender effects on muscle tone and mechanical properties have not been studied using hand-held myometric technology. Monitoring changes in muscle properties with ageing in community settings may provide a valuable assessment tool for detecting those at risk of premature decline and sarcopenia.ObjectiveThis study aimed to provide objective data on the effects of ageing and gender on muscle tone and mechanical properties of quadriceps (rectus femoris) and biceps brachii muscles.MethodsIn a comparative study of 123 healthy males and females (aged 18-90 years; n=61 aged18-35; n=62 aged 65-90) muscle tone, elasticity and stiffness were measured using the MyotonPRO device.ResultsStiffness was greater and elasticity lower in older adults for BB and RF (p<0.001). Tone was significantly greater in older adults for BB but not for RF when data for males and females were combined (p=0.28). There were no gender differences for BB in either age group. In RF, males had greater stiffness (young males 292 vs females 233 N/m; older males 328 vs females 311 N/m) and tone (young 16.4 vs 13.6 Hz; older 16.7 vs 14.9 Hz). Elasticity in RF was lower in young males than females but did not differ between the older groups (both males and females log decrement 1.6).ConclusionsStiffness and tone increased with ageing and elasticity decreased. These findings have implications for detecting frailty using a novel biomarker. Age and gender differences are important to consider when assessing effects of pathological conditions on muscle properties in older people

Innovation through reflection and collaboration: Students and clinicians learn side by side

The SLT programme run collaboratively by University of Greenwich and Canterbury Christ Church Universities, the Universities at Medway programme, is always looking for ways of bringing students together with experienced clinicians. Projects shared by practising clinicians and student practitioners provide rich learning opportunities. The Maori concept of “ako” - to learn is to teach and to teach is to learn - has profoundly influenced our approach to practice education. We feel that wisdom gets passed to students most effectively through the conversations that practitioners have about clients in context

Movement control testing of older people in community settings: description of a screening tool and intra-rater reliability

Objective: To determine the intra-rater reliability of a newly developed movement screening tool; the ‘Movement control screen for older people in community settings’. The movement screening tool aims to identify movement control impairments which can potentially influence movement function. Method: Thirty one active female recreational golfers, aged 65-77 years,carried out three movement control tests included in the screening tool. Performance was videorecorded to enable repeated ratings. Each test was evaluated by criteria which were rated as pass or fail and ratings were carried out three weeks apart to examine intra-rater reliability. Reliability was assessed using percentage agreement and Cohen’s Kappa. Results: Percentage agreementfor each test ranged from 93.0-97.3%, with an overall mean agreement of 95.5%. Kappa values for test scores ranged from 0.35-0.90. Percentage agreement for individual criteria ranged from 83.0-100.0%, with kappa values ranging from 0.00-1.00. Discussion: Acceptable intra-rater reliability was established for overall tests scores of the screening tool but certain criteria wereidentified as being less reliable than others. Recommendations are made for refinement of some criteria to improve reliability of the screening tool.<br/

Are there three main subgroups within the patellofemoral pain population? A detailed characterisation study of 127 patients to help develop targeted Intervention (TIPPs)

• Background Current multimodal approaches for the management of non-specific patellofemoral pain are not optimal, however, targeted intervention for subgroups could improve patient outcomes. This study explores whether subgrouping of non-specific patellofemoral pain patients, using a series of low cost simple clinical tests, is possible. • Method The exclusivity and clinical importance of potential subgroups was assessed by applying à priori test thresholds (1 SD) from seven clinical tests in a sample of adult patients with non-specific patellofemoral pain. Hierarchical clustering and latent profile analysis, were used to gain additional insights into subgroups using data from the same clinical tests. • Results One hundred and thirty participants were recruited, 127 had complete data: 84 (66%) female, mean age 26 years (SD 5.7) and mean BMI 25.4 (SD 5.83), median (IQR) time between onset of pain and assessment was 24 (7-60) months. Potential subgroups defined by the à priori test thresholds were not mutually exclusive and patients frequently fell into multiple subgroups. Using hierarchical clustering and latent profile analysis three subgroups were identified using 6 of the 7 clinical tests. These subgroups were given the following nomenclature: (i) ‘strong’, (ii) ‘weak and tighter’, and (iii) ‘weak and pronated foot’. • Conclusions We conclude that three subgroups of patellofemoral patients may exist based on the results of six clinical tests which are feasible to perform in routine clinical practice. Further research is needed to validate these findings in other datasets and, if supported by external validation, to see if targeted interventions for these subgroups improve patient outcomes