David Sainsbury

The effect of warm-up, static stretching and dynamic stretching on hamstring flexibility in previously injured subjects

BackgroundWarm-up and stretching are suggested to increase hamstring flexibility and reduce the risk of injury. This study examined the short-term effects of warm-up, static stretching and dynamic stretching on hamstring flexibility in individuals with previous hamstring injury and uninjured controls.MethodsA randomised crossover study design, over 2 separate days. Hamstring flexibility was assessed using passive knee extension range of motion (PKE ROM). 18 previously injured individuals and 18 uninjured controls participated. On both days, four measurements of PKE ROM were recorded: (1) at baseline; (2) after warm-up; (3) after stretch (static or dynamic) and (4) after a 15-minute rest. Participants carried out both static and dynamic stretches, but on different days. Data were analysed using Anova.ResultsAcross both groups, there was a significant main effect for time (p < 0.001). PKE ROM significantly increased with warm-up (p < 0.001). From warm-up, PKE ROM further increased with static stretching (p = 0.04) but significantly decreased after dynamic stretching (p = 0.013). The increased flexibility after warm-up and static stretching reduced significantly (p < 0.001) after 15 minutes of rest, but remained significantly greater than at baseline (p < 0.001). Between groups, there was no main effect for group (p = 0.462), with no difference in mean PKE ROM values at any individual stage of the protocol (p > 0.05). Using ANCOVA to adjust for the non-significant (p = 0.141) baseline difference between groups, the previously injured group demonstrated a greater response to warm-up and static stretching, however this was not statistically significant (p = 0.05).ConclusionWarm-up significantly increased hamstring flexibility. Static stretching also increased hamstring flexibility, whereas dynamic did not, in agreement with previous findings on uninjured controls. The effect of warm-up and static stretching on flexibility was greater in those with reduced flexibility post-injury, but this did not reach statistical significance. Further prospective research is required to validate the hypothesis that increased flexibility improves outcomes.Trial RegistrationACTRN12608000638336

Electromyographic analysis of the three subdivisions of gluteus medius during weight-bearing exercises

BackgroundGluteus medius (GM) dysfunction is associated with many musculoskeletal disorders. Rehabilitation exercises aimed at strengthening GM appear to improve lower limb kinematics and reduce pain. However, there is a lack of evidence to identify which exercises best activate GM. In particular, as GM consists of three distinct subdivisions, it is unclear if GM activation is consistent across these subdivisions during exercise. The aim of this study was to determine the activation of the anterior, middle and posterior subdivisions of GM during weight-bearing exercises.MethodsA single session, repeated-measures design. The activity of each GM subdivision was measured in 15 pain-free subjects using surface electromyography (sEMG) during three weight-bearing exercises; wall squat (WS), pelvic drop (PD) and wall press (WP). Muscle activity was expressed relative to maximum voluntary isometric contraction (MVIC). Differences in muscle activation were determined using one-way repeated measures ANOVA with post-hoc Bonferroni analysis.ResultsThe activation of each GM subdivision during the exercises was significantly different (interaction effect; p < 0.001). There were also significant main effects for muscle subdivision (p < 0.001) and for exercise (p < 0.001). The exercises were progressively more demanding from WS to PD to WP. The exercises caused significantly greater activation of the middle and posterior subdivisions than the anterior subdivision, with the WP significantly increasing the activation of the posterior subdivision (all p < 0.05).DiscussionPosterior GM displayed higher activation across all three exercises than both anterior and middle GM. The WP produced the highest %MVIC activation for all GM subdivisions, and this was most pronounced for posterior GM. Clinicians may use these results to effectively progress strengthening exercises for GM in the rehabilitation of lower extremity injuries.

Measurement of thigh muscle size using tape or ultrasound is a poor indicator of thigh muscle strength

Measurement of muscle size is often used to estimate muscle strength. The validity of these measurements as indicators of muscle strength is unclear however. This study investigated the relationship of two simple measures of muscle size (tape and ultrasound) with the concentric isokinetic quadriceps and hamstrings strength of a group of Irish Gaelic footballers (n = 25). Both tape and ultrasound demonstrated moderate to excellent reliability at measuring quadriceps and hamstrings muscle size (ICCs 0.69-0.99). Hamstrings were significantly stronger on the dominant limb at 60°/sec (p = 0.046) and 180°/sec (p = 0.005), but not at 300°/sec (p = 0.092). There was no significant difference in quadriceps strength at any speed (all p > 0.05). Dominant limbs were significantly larger using the tape measure (10 cm level: p = 0.005, mid-thigh level: p = 0.003). The dominant hamstrings (p < 0.001), but not the dominant quadriceps (p = 0.399), were significantly larger on ultrasound. There were statistically significant correlations between muscle strength and muscle size measurements, especially for the tape measurements. However, despite the fact that the dominant limb muscles were both stronger and larger, the strength of these correlations was only weak to moderate (r = 0.176-0.586). The results suggest that both tape measurement and ultrasound, while reliable, are of limited use as indicators of thigh muscle strength.

No deficit in hip isometric strength or concentric endurance in young females with mild patellofemoral pain

Previous research has linked deficits in hip muscle strengt h and endurance to patellofemoral pain syndrome (PFPS). This study investigated if females with mild PFPS displayed hip isometric strength and endurance deficits compared to un injured controls. Hip abduction, internal rotation (IR) and extern al rotation (ER) were assessed using an isokinetic dynamometer in 12 females with PFPS and 12 age- and gender-matched controls. Independent t-tests were used to examine between-group differences and Pearsons Correlation Coefficient examine d the relationship between isometric strength and endurance. No significant between-group differences for IR, ER and abduct ion strength or endurance were found (all p > 0.05). Strength and endurance measurements showed significant moderate correl ations for abduction (R = 0.496, p = 0.014) and ER (R = 0.592, p = 0.002) only. The PFPS subjects had mild pain (Numerical Rating Scale: mean 1.3 cm) and disability (Anterior Knee Pain Scale: mean 81/100), which may partly explain the lack of significant between-group differences. The results suggest th at female subjects with PFPS associated with mild pain and disability do not demonstrate hip IR, ER or abduction endurance or isometric strength deficits. Further research is required to clarify t he role of factors including hip strength and endurance in the management of more severe PFPS.