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Br J Sports Med. 2007 August; 41(8): 543–544.
PMCID: PMC2465454


Incidence, risk, and prevention of hamstring muscle injuries in professional rugby union

Brooks JHM, Fuller CW, Kemp SPT. Am J Sports Med 2006;34:1297–306

Professor Martin P Schwellnus, University of Cape Town, South Africa

BackgroundHamstring muscle injuries are common in professional rugby union, yet there are few well conducted studies to determine risk factors for these injuries in this sport.

Research question/sWhat are the incidence, severity and risk factors associated with hamstring muscle injuries in professional rugby union?

MethodologySubjects: 546 elite rugby football union players (300 forwards, 246 backs) (12 teams).

Experimental procedure: The cohort of players was followed over two seasons, and medical staff from each team documented match and training exposures as well as all hamstring muscle injuries (location, diagnosis, severity and mechanism) on a weekly basis. Injuries were defined based on loss of time from training and match play. Training (stretching (Stretch)), stretching and conventional strengthening exercises (Stretch+Strength) and additional Nordic strengthening exercises (+Nordic strength) were recorded.

Measures of outcome: Incidence of injury (injuries/1000 hrs play), severity (days lost), risk factors for injury.

Main finding/s:

  • Incidence (per 1000 hrs) of hamstring muscle injuries: higher in matches (5.6) vs training (0.27); during matches was higher in backs (8.6) vs forwards (3.0). Running accounted for 68% of the hamstring injuries.
  • Risk factors: a previous injury <1 month ago, and training >12.5 hrs in the preceding week were associated with increased risk of severe injury.

Conclusion/sHamstring muscle injuries are common in elite rugby union players, but may be reduced by limiting training hours, delaying return to play following a previous injury and using a combination of stretching, strengthening and Nordic eccentric training exercises.

Evidence based rating8/10

Clinical interest rating8/10

Type of studyProspective cohort study

Methodological considerationsWell conducted study, large sample size

Keywordshamstring, injury, risk factors, rugby union, stretching, strengthening, Nordic hamstring exercise

Low‐intensity pulsed ultrasound accelerates bone‐tendon junction healing: a partial patellectomy model in rabbits

Lu H, Qin L, Fok P. Am J Sports Med 2006;34:1287–96

BackgroundThere is some evidence that low‐intensity pulsed ultrasound accelerates fracture healing, delayed union, nonunion, and soft tissue repair.

Research question/sDoes low‐intensity pulsed ultrasound accelerate healing of bone‐to‐tendon junction repair in an animal model by promoting osteogenesis and tissue remodelling at the healing junction?

MethodologyAnimals 48 rabbits, 18 weeks old.

Experimental procedure: All the animals were subjected to a standard partial patellectomy and were then randomly divided into two groups: ultrasound treatment (“US” group: daily US (20 min) from 3 days treatment after surgery onto the patellar tendon‐patella healing junction and continuously up to weeks 2, 4, 8 and 16 postoperatively) and a control group (CON). The patella‐patellar tendon complexes were harvested and analysed.

Measures of outcome: Radiographic, histologic and biomechanical evaluation.

Main finding/s:

  • Radiographic assessment: there was significantly more newly formed bone at the patellar tendon‐patella healing junction in the US group compared with the CON group at week 8 (4.91±2.74 mm2 vs 2.50±1.83 mm2, p<0.05) and week 16 (7.22±2.34 mm2 vs 4.61±2.22 mm2, p<0.05) after partial patellectomy.
  • Histologic assessment: there was improved tissue integration and earlier bone formation in the US group compared with the CON group at weeks 8 and 16.

In an animal model, daily low‐intensity pulsed ultrasound was able to accelerate bone‐to‐tendon junction repair.

These results may accelerate bone‐to‐tendon junction repair facilitating earlier rehabilitation in human subjects, but clinical studies are required.

Evidence based rating8.5/10

Clinical interest rating8/10

Type of studyRandomised controlled trial (animal model)

Methodological considerationsWell conducted study, application to human tissue needs to be studied

Keywordsbone‐to‐tendon junction repair, low‐intensity pulsed ultrasound (LIPUS), animal study, partial patellectomy model, mechanical properties

Humidity influences exercise capacity in subjects with exercise‐induced bronchoconstriction (EIB)

Stensrud T, Berntsen S, Carlsen K‐H. Resp Med 2006;100:1633–41

BackgroundIt has been documented that exercise‐induced bronchoconstriction (EIB) decreases in humid air and increases in cold and dry air, but the effect of humid environment on exercise capacity in subjects with EIB has not been well studied.

Research question/sDo changes in humidity of the environmental air affect exercise capacity [peak oxygen uptake (VO2peak), peak ventilation (VEpeak) and peak running speed (Vpeak)] and EIB in subjects suffering from EIB?

MethodologySubjects: 20 subjects (10–45 yrs old, male  = 13, females  = 7) with diagnosed EIB.

Experimental procedure: All the subjects performed exercise testing in two randomised conditions on different days: (1) standardised, regular environmental conditions (control group (CON)): 20.2°C, 40% relative humidity) and (2) under standardised humid environmental conditions (HUM: 19.9°C, 95% relative humidity). Heart rate (HR), oxygen uptake (VO2), respiratory gas exchange ratio (RER), breathing frequency (BF) and minute ventilation (VE) were measured during exercise, and lung function was measured before and 1, 3, 6, 10 and 15 min after exercise.exercise.

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Measures of outcome: Exercise performance (VO2peak), EIB (post‐exercise decrease in FEV1).

Main finding/s:

Other parameters: HRpeak increased significantly while BFpeak decreased significantly in the HUM condition; RERpeak and VEpeak did not change significantly.

Conclusion/sIn subjects diagnosed with EIB, exercise performed in a humid environment (95% relative humidity) improves exercise performance (VO2peak) and reduces bronchoconstriction (smaller decrease in FEV1 post‐exercise).

Evidence based rating8/10

Clinical interest rating8/10

Type of studyRandomised controlled clinical trial

Methodological considerationsWell conducted study

Keywordspeak oxygen uptake, exercise capacity, environmental humidity, exercise‐induced bronchoconstriction

Activity level among adolescents with migraine

Dooley JM, Gordon KE, Wood EP. Paediatr Neurol 2006;35:119–21

BackgroundOne of the personality traits of adolescents with migraine has been described as “less physically enduring”, therefore the physical activity profile in these adolescents may be decreased.

Research question/sAre reported exercise habits of adolescents (aged 12–19 years) with migraine less than those without migraine?

MethodologySubjects: 17 549 adolescents from a larger study (Canadian Community Health Survey) who answered a question about migraine.

Experimental procedure: Of the respondents, 6470 indicated that they were diagnosed by a health professional as suffering from migraine (MIG group) while the remainder did not suffer from migraine (control group (CON)). Exercise activities including sports and other activities were recorded in both groups.

Measures of outcome: Daily exercise activities between groups.

Main finding/sDaily activity: subjects in the MIG group reported more physical activity (increased level of physical activity for a usual day, increased energy expenditure, increased monthly frequency of physical activity of >15 min) than those in the CON group (when corrected for age and sex) (p<0.05).

Conclusion/sAdolescents suffering from migraine are, in general, more physically active than their peers without migraine.

Evidence based rating7/10

Clinical interest rating7.5/10

Type of studyCase control study

Methodological considerationsNo cause effect can be determined

Keywordsmigraine, headaches, adolescents, physical activity

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