Randomised trial of the effects of four weeks of daily stretch on extensibility of hamstring muscles in people with spinal cord injuries

The aim of this assessor-blind randomised controlled trial was to determine the effect of four weeks of 30 minute stretches each weekday on extensibility of the hamstring muscles in people with recent spinal cord injuries. A consecutive sample of 16 spinal cord-injured patients with no or minimal voluntary motor power in the lower limbs and insufficient hamstring muscle extensibility to enable optimal long sitting were recruited. Subjects' legs were randomly allocated to experimental and control conditions. The hamstring muscles of the experimental leg of each subject were stretched with a 30 Nm torque at the hip for 30 minutes each weekday for four weeks. The hamstring muscles of the contralateral leg were not stretched during this period. Extensibility of the hamstring muscles (hip flexion range of motion with knee extended, measured with a 48 Nm torque at the hip) of both legs was measured by a blinded assessor at the commencement of the study and one day after the completion of the four-week stretch period. Changes in hamstring muscle extensibility from initial to final measurements were calculated. The effect of stretching was expressed as the mean difference in these changes between stretched and non-stretched legs. The mean effect of stretching was 1 degree (95% CI -2 to 5 degrees). Four weeks of 30 minute stretches each weekday does not affect the extensibility of the hamstring muscle in people with spinal cord injuries.     

Can apparent increases in muscle extensibility with regular stretch be explained by changes in tolerance to stretch?

The aim of this study was to determine whether an intensive stretch program increases muscle extensibility or subjects' tolerance to an uncomfortable stretch sensation. Twenty healthy able-bodied individuals with limited hamstring muscle extensibility were recruited. A within-subjects design was used whereby one leg of each subject was randomly allocated to the experimental condition and the other leg was allocated to the control condition. The hamstring muscles of each subject's experimental leg were stretched for 20 minutes each weekday for four weeks. Hamstring muscle extensibility (angle of hip flexion corresponding with a standardised torque) and stretch tolerance (angle of hip flexion corresponding with maximal torque tolerated) were assessed on both legs at the beginning and end of the study. The intervention did not increase the extensibility of the hamstring muscles (mean change in hip flexion was -1 degree, 95% CI -4 to 3 degrees) but did increase subjects' tolerance to an uncomfortable stretch sensation (mean change in hip flexion was 8 degrees, 95% CI 5 to 12 degrees). These results highlight the importance of distinguishing between real and apparent increases in muscle extensibility when assessing the effectiveness of stretch, and indicate that whilst a four-week stretch program increases subjects' tolerance to an uncomfortable stretch sensation it does not increase hamstring muscle extensibility.     

Previous hamstring muscle strain injury alters passive tissue stiffness and vibration sense

BackgroundHamstring strain is one of the most common among sports injuries. A previous history of this injury is considered a strong predictor of recurrent hamstring strain injury. It has been suggested that fascial tissue alters after muscle strain injury. However, the association between previous hamstring strain injury and tissue stiffness and vibration sense detection has not been investigated.ObjectivesWe aimed to determine whether a previous history of hamstring strain injury affects tissue stiffness and vibration sense in professional soccer players.MethodThe stiffness (MyotonPRO®) and vibration disappearance threshold (tuning fork) were measured in eight professional soccer players with previous history of hamstring strain and eight uninjured players. The differences between two groups’ means were analyzed. Side-to-side differences between injured and uninjured legs were also analyzed. Results: The tissue stiffness was higher, and the vibration disappearance threshold was lower, in previously injured players when compared to uninjured players. Similar differences were found between injured and uninjured legs. No significant relationship was detected between the age or body mass index (BMI) for both tissue stiffness and vibration disappearance threshold (all P < 0.05).ConclusionsSoccer players with a previous history of hamstring strain injury exhibited higher tissue stiffness and lower vibration sensitivity in the injured leg, regardless of the age and BMI. The results that players who have a previous hamstring strain injury with altered tissue stiffness and vibration sense will be useful and feasible evaluation for chronic muscle strain condition.     

Influence of age and physical activity on isokinetic characteristics of hamstring and quadriceps muscles of young gymnasts and soccer players]

OBJECTIVE: The aim of this work is the assessment of age and sport influences on the isokinetic knee muscle characteristics. SUBJECTS AND METHOD: Subjects performed a bilateral knee flexion/extension test on an isokinetic device at 60 and 180 degrees.s(-1) speed in concentric mode. The three parameters studied in this work were the Peak Torque, Average Power and hamstring/quadriceps ratio. Thirty-eight soccer players (16,6 +/- 1.4 years old) and 22 gymnasts (18 +/- 2.8 years old) were tested. The population was separated into three groups : 15 years old, 17 years old, 20 years old. RESULTS: The isokinetic values of soccer players were significantly higher (p < 0.0001) than those of the the gymnasts. The isokinetic values of the oldest soccer players were significantly higher (0.005 < p < 0.05) for hamstrings than those of the younger soccer players. The isokinetic values of the oldest gymnasts were significantly higher (0.005 < p < 0.05) for the quadriceps than those of the younger gymnasts. There were no significant differences between dominant and non dominant limbs in soccer players. CONCLUSION: In the present study, the muscular maturation improves the absolute strength of the older sportsmen in comparison to the younger. Soccer favor most the absolute strength of the inferior member in comparison to the gymnastics.     

Importance of correcting isokinetic peak torque for the effect of gravity when calculating knee flexor to extensor muscle ratios

The purpose of our investigation was to compare, for the hamstring and quadriceps femoris muscles, peak torque values uncorrected for gravity with the peak torque values corrected for gravity and to determine the effect of making this correction on the hamstring to quadriceps femoris muscle peak torque ratio at slow and fast isokinetic speeds. We measured peak torques isokinetically at 60 degrees/sec (slow) and 240 degrees/sec (fast) in 25 female university soccer players. The gravity effect torque (GET) is the torque resulting from the effect of gravity on the combined weight of the leg and dynamometer arm at the precise angle of extension and flexion peak torque. The GET was added to the measured quadriceps femoris muscle peak torque and subtracted from the hamstring muscle peak torque to yield gravity corrected values. Failure to consider GET greatly underestimated quadriceps femoris muscle torque and overestimated hamstring muscle torque and the ratio between these torques at both speeds. Whereas the uncorrected hamstring to quadriceps femoris muscle peak torque ratio increased as speeds went from 60 degrees/sec to 240 degrees/sec, the gravity corrected ratio significantly decreased. Clinicians must remember the importance of making the gravity correction in patients with reduced torque output where the gravitational torque is a greater percentage of the measured torque to ascertain correctly the relative strength of antagonists inversely affected by gravity.     

Intrinsic and imposed hamstring length influence posterior pelvic rotation during hip flexion

BACKGROUND: The contribution of posterior tilt of the pelvis (pelvic rotation) to hip flexion has been described for individuals who are standing, supine, and suspended. The effects of intrinsic and imposed hamstring length on the motion have not been investigated in a controlled manner. This study investigated the influence of intrinsic and imposed hamstring length on pelvic rotation during bilateral active hip flexion. METHODS: Intrinsic hamstring length was characterized by the maximal active straight leg raise angle. Hamstring length was imposed by immobilizing the knees in 0 degrees, 45 degrees, and 90 degrees of flexion. Pelvic and thigh segments were marked with reflective spheres. Subjects' saggital plane motion was captured using computerized motion analysis during bilateral hip flexion while both knees were immobilized in three positions. Multifactorial analysis of variance was employed to show the effect of intrinsic and imposed hamstring length on pelvic rotation. FINDINGS: Pelvic rotation occurred throughout the hip flexion range of motion. Pelvic rotation was influenced significantly by hip flexion angle, knee position, the interaction between hip flexion angle and knee position, and the interaction between hip flexion angle, knee position, and active straight leg raise angle. INTERPRETATION: Both intrinsic and imposed hamstring length influence pelvic rotation during bilateral hip flexion. These influences should be considered by clinicians who have individuals engage in hip flexion maneuvers.     

Conséquences et prédiction des lésions musculaires des ischiojambiers à partir des paramètres isocinétiques concentriques et excentriques du joueur de football professionnelConsequences and prediction of hamstring muscle injury with concentric and eccentric isokinetic parameters in elite soccer players

OBJECTIVE: To know if isokinetic parameters identify previous hamstring (H) injury and predict a new muscle injury in high-level soccer player. METHOD: Concentric (con) and eccentric (ecc) isokinetic torque was measured at the angular speed of 60 degrees /s in 28 elite soccer players (23 years +/- 3.3; 74 kg +/- 7.5; 178 cm +/- 6.5). First, 11 players, victims of 15 moderate or major hamstring injuries in the preceding 2 years, were compared with 17 players without previous hamstring injury. Comparisons were carried out from isokinetic knee flexors-extensors ratios [Hcon/Qcon and Hecc/Qcon] and bilateral knee flexors ratios [Hcon/Hcon and Hecc/Hecc]. Secondly, all the population was followed during 12 months and the isokinetic muscular profile of players who presented a recurrence or a new hamstring muscle injury was analysed. RESULTS: A concentric ratio hamstring-to-quadriceps lower than 0.6 and a hamstring asymmetry of more than 10% do not allow to identify previous hamstring injury. On the other hand, the mixed ratio eccentric hamstring-to-concentric quadriceps lower than 0.6 represents the best indicator (probability: 77.5%). The rate of recurrence is 30% (three cases of 10) and the rate of new hamstring muscle injury is 31% (five cases of 16) (P > 0.05). One of the five injured soccer players presented a concentric ratio hamstring-to-quadriceps lower than 0.6 and no player presented a mixed ratio lower than 0.6. However, four of the five injured players presented a concentric and an eccentric asymmetry. But, it is the strongest side, which presented a new hamstring muscle injury. CONCLUSION:The mixed ratio eccentric hamstring-to-concentric quadriceps lower than 0.6 identify a previous hamstring injury despite the resumption of competitive soccer. However, this ratio and the others isokinetic studied parameters do not predict a recurrence or a new hamstring muscle injury.     

The Neuromuscular Effects of the Copenhagen Adductor Exercise: A Systematic Review

BackgroundGroin strains are one of the most common time-loss injuries in athletes. The Copenhagen Adductor Exercise (CAE) eccentrically strengthens the adductors and may function to prevent adductor strains, similar to the eccentric mechanism in which the Nordic Hamstrings exercise acts to prevent hamstring strains.ObjectiveThe purpose of this study was to systematically review the literature on the CAE and its effects on adductor muscle strength and muscle activity in athletes.Study DesignSystematic ReviewMethodsA systematic search of the literature was performed in the following databases: Pubmed; Medline (EBSCO); Sportdiscus; Scopus; Web of Science; CINAHL; Proquest; Cochrane Library; Physiotherapy Evidence Database (PEDro). Inclusion criteria consisted of 1) implements CAE, 2) includes athletes of any age participating in at least one sport, 3) study type is a cohort study or randomized control trial. Studies were excluded if they were not written in English or did not measure strength as an outcome. Data were extracted on eccentric hip adductor strength (EHAD), eccentric hip abductor strength (EHAB), EHAD:EHAB ratio, and electromyography (EMG) activity of the adductor muscles. Quality assessment was performed on all included studies using Quality Assessment Tool for Quantitative Studies.ResultsFive articles were identified for inclusion, four of which received a strong rating, and one a moderate rating on the Quality Assessment Tool for Quantitative Studies. The CAE significantly increased EHAD in four of the four studies that examined it; significantly increased EHAB and EHAD:EHAB in three of the three studies that examined them, and increased the EMG activity of the adductors in the dominant leg 108%.ConclusionOverall, the CAE increases EHAD, EHAB, EHAD:EHAB, and EMG activity in the hip adductors in male soccer players. The increase in strength may reduce adductor muscle injuries, although more research needs to be done in this area to identify a clear relationship between the CAE and groin injury prevention.Level of Evidence1b     

Passive moment about the hip in straight leg raising

OBJECTIVE: The purpose of this examine is to study the load-deformation characteristics of the hip in straight leg raising. DESIGN: An experimental study in which passive moment about the hip was determined as a function of hip angle. BACKGROUND: Straight leg raising is widely employed in clinical examination, and there is little information on its mechanical characteristics. METHODS: Fourteen healthy volunteers were recruited for this study. Three trials of straight leg raise tests were performed while subjects lay supine on a plinth that was fitted with load cells. An electrogoniometer was employed to measure hip flexion during the test. Resistive moment at the hip was determined using a dynamic biomechanical model. RESULTS: The present experimental method was shown to be highly reliable. The moment-angle curves of all subjects were shown to follow an exponential function. CONCLUSION: Stiffness and strain energy of posterior hip tissues could be derived from the moment-angle curves. Evaluation of such elastic properties is clinically important as they may be altered with injuries of the tissues. RELEVANCE: Clinically, contracture of hamstring muscles and other posterior hip tissues is evaluated by measuring the available range of hip flexion in straight leg raising. However, this does not provide any information on the elastic properties of the tissues. The present study reports a reliable method of evaluating such properties.     

Effects of posture and lower limb muscle strength on the results of the Star Excursion Balance Test

[Purpose] This study aimed to clarify the relationship between the distance measurements in the Star Excursion Balance Test and participants’ posture and lower limb muscle strength. [Participants and Methods] Nine healthy male college students participated in this study. Star Excursion Balance Test distance was measured in both lower limbs by performing anterior, posterolateral, and posteromedial trials; measuring the maximum reach; and performing three-dimensional motion analysis to determine the posture at maximum reach. Isokinetic muscle strength for knee flexion/extension, hip flexion/extension, and hip adduction/abduction were measured using an isokinetic machine. [Results] The hip extension strength, reach side ankle dorsiflexion angles, stance side knee flexion, reach side knee flexion, and knee flexion strength were selected as significant explanatory variables in the anterior direction. For the posteromedial direction, hip adduction and hip extension strength, reach side hip flexion angle, and stance side hip flexion angle were selected. For the posterolateral direction, reach side knee flexion angle and stance side ankle dorsiflexion, knee flexion strength and reach side hip flexion angle were selected. [Conclusion] The related factors differed between the dominant and non-dominant legs even in the same reach direction.     

Isokinetic, functional and proprioceptive assessment of football players two years after surgical reconstruction of the anterior cruciate ligament of the knee]

Injuries to the anterior cruciate ligament (ACL) of the knee are common in sport and are treated routinely in the world of sports medicine. In order to resume competitive sport in safety, it is important to know the actual level of performance achieved by the operated leg some time after the ligament repair. OBJECTIVES: The objective of this work was to evaluate the recovery of the operated leg in Tunisian sportsmen two years after surgery by using isokinetic testing (60 degrees s(-1)), the one-leg hop distance test (i.e. a functional activity that one often finds in sport) and proprioceptive assessment. A secondary objective was to detect any possible correlations between the various outcomes. MATERIALS AND METHOD: The ACL group was composed of 26 top-level Tunisian footballers having undergone ACL ligament repair. Two years after surgery, the following assessments were performed: an isokinetic test with an angular velocity of 60 degrees s(-1), a proprioceptive assessment in both active and passive modes and the functional one-leg hop distance test. RESULTS: Our investigations confirmed a muscle deficit of 16% in the hamstring muscles of the injured leg. In both active and passive modes, normal proprioception is observed at a flexion of 60 degrees and in total extension but not in a mid-way position. The performance level of the operated leg (in terms of distance) had an average symmetry value of 93.40+/-2.7%. CONCLUSION: Playing football appears to influence the isokinetic strength profile in sportsmen after ACL repair. The repair procedure leads to bilateral proprioceptive disruption at 15 degrees of knee flexion, on average.     

A systematic review of surgical intervention in the treatment of hamstring tendon ruptures: current evidence on the impact on patient outcomes

Hamstring injuries are among the most common muscle injuries. They have been reported in many different sports, such as running, soccer, track and field, rugby, and waterskiing. However, they are also present among the general population. Most hamstring injuries are mild strains, but also moderate and severe injuries occur. Hamstring injuries usually occur in rapid movements involving eccentric demands of the posterior thigh. Sprinting has been found to mainly affect the isolated proximal biceps femoris, whereas stretching-type injuries most often involve an isolated proximal injury of the semimembranosus muscle. The main cause of severe 2- or 3-tendon avulsion is a rapid forceful hip flexion with the ipsilateral knee extended. Most hamstring injuries are treated non-surgically with good results. However, there are also clear indications for surgical treatment, such as severe 2- or 3-tendon avulsions. In athletes, more aggressive recommendations concerning surgical treatment can be found. For a professional athlete, a proximal isolated tendon avulsion with clear retraction should be treated operatively regardless of the injured tendon. Surgical treatment has been found to have good results in severe injuries, especially if the avulsion injury is repaired in acute phase. In chronic hamstring injuries and recurring ruptures, the anatomical apposition of the retracted muscles is more difficult to be achieved. This review article analyses the outcomes of surgical treatment of hamstring ruptures. The present study confirms the previous knowledge that surgical treatment of hamstring tendon injuries causes good results with high satisfaction rates, both in complete and partial avulsions. Early surgical repair leads to better functional results with lower complication rates, especially in complete avulsions.

KEY MESSAGEs

• Surgical treatment of hamstring tendon ruptures leads to high satisfaction and return to sport rates.
• Both complete and partial hamstring tendon ruptures have better results after acute surgical repair, when compared to cases treated surgically later.
• Athletes with hamstring tendon ruptures should be treated more aggressively with operative methods.

     

Hip Adduction and Abduction Strength Profiles Among Bantam,High School,Juniors, and Collegiate American Ice Hockey Players

BackgroundAdductor strains are the most common non-contact musculoskeletal injury sustained in ice hockey. Systematic reviews have determined higher level of play and lower hip adduction to abduction strength ratios to be associated with an increased risk of adductor strain across multiple sports. Limited research exists regarding hip adduction and abduction strength profiles across various levels of ice hockey players.PurposeTo compare isometric hip adduction and abduction strength profiles among bantam, high school, tier one juniors, and NCAA Division I collegiate ice hockey players. A secondary purpose was to identify whether differences in strength profiles between dominant and non-dominant limbs exist.Study DesignCross-sectional cohort study.MethodsA questionnaire of demographic data, hockey, and injury specific information was completed by all subjects. The mean of three reps of maximal hip isometric adduction and abduction strengths were quantified using a handheld dynamometer with external belt-fixation. Ratios of hip adduction-to-abduction strength were calculated and normalized for body weight.ResultsA total of 87 uninjured skaters were included in this study with a mean age of 17 years. Mean hip adductor-to-abductor ratios for Bantam hockey players were 121% followed by collegiate (115%), Juniors (111%), and high school (109%) hockey players. No statistically significant differences were found between peak hip adduction and abduction isometric strength and playing level. In addition, there was no difference between unilateral hip strength ratios and shooting hand or leg dominance. While 34.5% of subjects reported a history of adductor injury, no significant differences existed regarding strength ratios during bilateral comparison or when compared to their team norms. Three subjects were found to have unilateral ratios of less than 80%, while two subjects demonstrated bilateral ratios of less than 80%.ConclusionsSymmetry is illustrated between dominant and non-dominant legs in ice hockey players with and without a history of adductor injury. Results align well with previously established cross-sectional data from Australian football, with ratios of 103% in high school players, 107% in semi-professional players, and 113% in collegiate players.Level of EvidenceLevel 3     

Application of Shear-Wave Elastography in the Evaluation of Hamstring Stiffness in Young Basketball Athletes

BackgroundPrevious literature has postulated a relationship between greater hamstring stiffness and a higher risk of sustaining injury. Shear wave elastography (SWE) presents a relatively new means for non-invasive evaluation of soft tissue elasticity pre- and post- injury or intervention.Purpose1. To establish baseline hamstring stiffness measures for young competitive athletes and (2) determine effect of targeted neuromuscular training (TNMT) on shear wave stiffness of the hamstring.Study DesignUn-blinded, prospective, non-randomized, cohort study.MethodsSix-hundred forty-two lower extremities from 321 high school and collegiate basketball athletes (177 F: 139 M) were examined for hamstring stiffness prior to the start of their competitive basketball season. Teams were cluster assigned to either the control or intervention (TNMT) group. Subjects in the control group underwent regular season activities as directed, with no influence from the research team. For the TNMT group, the research team introduced a hamstring targeted dynamic warm-up program as an intervention focused on activating the hamstring musculature.ResultsCollegiate status was significant to hamstring stiffness for both sexes (p ≤ 0.02), but hamstring stiffness did not correlate to age or sex (r² ≤ 0.08). Intervention was a significant factor to hamstring stiffness when the hip was positioned in extension (p ≤ 0.01), but not in deeper flexion (p = 0.12). This effect was sex-specific as TNMT influenced hamstring stiffness in females (p = 0.03), but not in males (p ≥ 0.13). Control athletes suffered three HAM injuries; TNMT athletes suffered 0 hamstring injuries.ConclusionHigher SWE measurements correlated with increased risk of injury, male sex, and collegiate athletics. TNMT intervention can lessen muscle stiffness which may reduce relate to injury incidence. Intervention effectiveness may be sex specific.Level of EvidenceII     

Effects of Sex and Age on Quadriceps and Hamstring Strength and Flexibility in High School Basketball Athletes

BackgroundEccentric hamstring strength and hamstring/quadriceps strength ratios have been identified as modifiable risk factors of hamstring strains. Additionally, those strength and flexibility characteristics are commonly used as clinical tests to monitor progress of athletes with acute or chronic hamstring strains. Although hamstring strains are common among basketball athletes, normative values of knee strength and flexibility characteristics are scarce. Normative values for these athletes would be important in prevention and management of hamstring strains.PurposeTo establish quadriceps and hamstring isokinetic strength and flexibility values among high school basketball athletes and examine the effects of sex and age.Study DesignCross-sectional researchMethodsIsokinetic knee muscular strength (concentric quadriceps [QuadC], concentric hamstring [HamC], eccentric hamstring [HamE], and strength ratios ([HamC/QuadC and HamE/Quad]), flexibility of hip flexors and quadriceps during a Modified Thomas test, and flexibility of hip extensors and hamstring during passive straight leg raise (SLR) and passive knee extension (PKE) tests were measured. Effects of sex and age were analyzed using t-tests and analysis of variance, respectively with Bonferroni corrected post hoc tests (p≤0.01).ResultsA total of 172 high school basketball athletes (64 males/108 females; mean age (range): 15.7 (14-18) years old) participated in the study. Male athletes were significantly stronger than female athletes (QuadC: p<0.001; HamC: p<0.001) while no differences were observed in strength ratio (HamC/QuadC: p=0.759-0.816; HamE/QuadC: p=0.022-0.061). Among male athletes, a significant effect of age on quadriceps and hamstring strength was observed: older male athletes were stronger than younger male athletes. Contrarily, there were no effects of age on strength among female athletes. There were significant sex differences in quadriceps flexibility, SLR, and PKE (female athletes were more flexible; p=0.001-0.005) while no sex differences were found in hip flexor flexibility (p=0.105-0.164). There were no effects of age for any flexibility variables within male and female athletes (p=0.151-0.984).ConclusionThe current results provide normative values for hamstring strength and flexibility in high school basketball athletes. These normative values may further assist sports medicine specialists to develop screening tests, interventions, and return-to-sport criteria in this population.Level of Evidence3B     

Lumbopelvic exercise reduces lower limb muscle strain injury in recreational athletes

Abstract

Background: Lower limb muscle strain injury (LLMSI) has a high incidence in sport. Reports of injury reduction after lower limb stretching and strengthening interventions have been inconsistent; however, it has been proposed that poor proximal control may predispose athletes to LLMSI. Deficits in lumbopelvic stabilizers, reduced trunk control, pelvic strength imbalance, poor balance and reduced hip flexibility have been reported as risk factors for leg muscle injuries including hamstring, groin and thigh strain. Exercise interventions targeting the lumbopelvic region may be effective in preventing LLMSI.

Objective: To determine if lumbopelvic exercise interventions reduce the incidence of LLMSI.

Methods: Databases were searched for exercise trials that targeted the lower back, abdomen, pelvis and hip. The search included a range of interventions: lumbopelvic stability, resistance training, muscle stretching and posture or balance exercise. Quality of included trials was assessed using the PEDro scale.

Results: Six studies were identified that compared lumbopelvic exercise with other interventions or usual training and reported the incidence of LLMSI. Lumbopelvic exercise intervention was favoured with a significant effect size both in a meta-analysis (OR?=?0·40, 95% CI 0·17–0·94, P?=?0·03) and in a sensitivity analysis based on one high quality study (OR?=?0·27, 95% CI 0·09–0·75, P?=?0·01). Sub-group analysis of three balance studies did not show a significant effect in reducing LLMSI.

Conclusions: Lumbopelvic exercise reduces the incidence of LLMSI. Stabilization, agility and neuromuscular were the most successful interventions.     

Salbutamol, a beta 2-adrenoceptor agonist, increases skeletal muscle strength in young men.

1. beta 2-Adrenoceptor agonists have been shown to increase rapidly lean body mass and reverse muscle wasting in several animal models of human illness. However, no published information is available for humans. In the present study, we investigated the effects of a slow-release preparation of salbutamol or a placebo on skeletal muscle functional capacity in 12 healthy men. The strength of different muscle groups was measured on two occasions before and after 14 and 21 days of treatment. 2. No significant changes in muscle strength were observed with placebo during the trial. In contrast, the strength of both quadriceps muscles increased significantly (12 +/- 3%) after 14 days on salbutamol, and remained elevated at 21 days. Whereas the strength of the hamstring muscles of the dominant leg significantly increased after 21 days on salbutamol (22 +/- 6%), the strength of the non-dominant hamstring muscles returned to baseline values. 3. There was no significant change in the grip strength of either hand in these subjects during the trial. The maximal static inspiratory mouth pressure increased significantly (7 +/- 2%) after 14 days on salbutamol, and increased further after 21 days (15 +/- 4%); the expiratory mouth pressure remained constant. No significant changes in body weight, skinfold thickness, lean body mass or limb circumferences were measured in either group. 4. These data demonstrate that short-term administration of salbutamol increases voluntary muscle strength in man. However, the magnitude and duration of this effect vary between muscle groups. This study implies that the beta 2-adrenoceptor agonists may be of therapeutic potential in altering skeletal muscle function in humans.     

Reliability of hand-held dynamometry in assessment of knee extensor strength after hip fracture

OBJECTIVES: To examine the reliability of hand-held dynamometry in assessing knee extensor strength in inpatients undergoing rehabilitation after hip fracture and to examine the discriminant validity of this measure. DESIGN: A total of 16 subjects (14 women; mean +/- SD, 79 +/- 7 yrs) undergoing inpatient rehabilitation after hip fracture volunteered to participate. Isometric knee extensor strength of the fractured and unfractured sides was determined with a hand-held dynamometer. Subjects were retested 1-2 days after the initial testing session. RESULTS: Test-retest intraclass correlation coefficients were high for both the fractured (0.91) and unfractured legs (0.90). A low coefficient of variation was observed for both the fractured (15.3%) and unfractured (14.7%) sides. The maximal knee extensor strength was significantly different when comparing the fractured (7.9 +/- 3 kg) and unfractured (15.6 +/- 4 kg) legs. When comparing test 1 and test 2 mean values for the fractured leg, the scores significantly differed (t = 3.14, P < 0.01), with 13 of 16 subjects scoring higher on test 2. CONCLUSIONS: Hand-held dynamometry is a reliable and valid tool for assessment of knee extensor strength after hip fracture. Reduced knee extensor strength in the fractured leg may be an important component limiting rehabilitation progress in these patients.     

Muscle fatigue in the gluteus maximus changes muscle synergies during single-leg landing

IntroductionHamstring strain often occurs at the end of a match or during practice in sports activities. The gluteus maximus muscle is an important muscle for hip extension along with the hamstring. Gluteus maximus muscle dysfunction may be involved in the occurrence of hamstring strain. Therefore, we focused on gluteus maximus muscle fatigue and investigated gluteus maximus and hamstring coordination.MethodsHe activities of the right side of the erector spinae, internal oblique, upper, and lower gluteus maximus fibers, gluteus medius, rectus femoris, semitendinosus, and medial head of the gastrocnemius muscle were measured in 21 young healthy men during single-leg landing before and after fatigue intervention. Fatigue intervention of the gluteus maximus muscle was performed using electrical muscle stimulation. Electromyography data were analyzed using non-negative matrix factorization. Additionally, to evaluate gluteus maximus fatigue, an isometric hip extension strength test and frequency analysis were performed before and after the intervention.ResultsThe isometric strength power and median frequency significantly decreased after intervention. Two muscle synergies were extracted and the contribution of semitendinosus of a synergy that was activated just before landing, significantly increased due to the intervention.DiscussionThe results of the isometric hip strength test and frequency analysis, the gluteus maximus fatigued by the intervention. The hip extensor muscles eccentrically contract to absorb the ground reaction force during landing. Therefore, our results may suggest that the eccentric load increases for the hamstring due to gluteus maximus muscle fatigue and may be a risk factor for hamstring strain.