Warm-up and stretching in the prevention of muscular injury

Muscular injury is one of the major problems facing today's athletes, both recreational and professional. Injuries to skeletal muscle represent >30% of the injuries seen in sports medicine clinics. As a result, it is imperative to utilise the most effective means to aid in deterring these injuries. However, there are conflicting opinions regarding methods of reducing muscular injury through warm-up and stretching techniques.Therefore, the purpose of this article is to examine the potential of a warm-up and/or stretching routine in deterring muscular injury during physical activity. The article examines a variety of studies regarding warm-up, stretching and muscular injury. The article also provides a definition of warm-up and stretching to provide clarity on this topic. Many of the differences within previous research were due to conflicting definitions. We also address this issue by examining research on muscular injury and physical adaptations to muscular injury and training.This article provides contradictory evidence to conclusions that have been drawn in previous review articles, which determined that warm-up and/or stretching protocols did not deter injury. The research included here conveys that certain techniques and protocols have shown a positive outcome on deterring injuries. As a result, a warm-up and stretching protocol should be implemented prior to physical activity. The routine should allow the stretching protocol to occur within the 15 minutes immediately prior to the activity in order to receive the most benefit. In addition, current information regarding improvements in flexibility is reviewed.     

Motor learning strategies in basketball players and its implications for ACL injury prevention: a randomized controlled trial

Purpose

Adding external focus of attention (EF, focus on the movement effect) may optimize current anterior cruciate ligament (ACL) injury prevention programmes. The purpose of the current study was to investigate the effects of an EF, by a visual stimulus and an internal focus, by a verbal stimulus during unexpected sidestep cutting in female and male athletes and how these effects remained over time.

Methods

Ninety experienced basketball athletes performed sidestep cutting manoeuvres in three sessions (S1, S2 and S3). In this randomized controlled trial, athletes were allocated to three groups: visual (VIS), verbal (VER) and control (CTRL). Kinematics and kinetics were collected at the time of peak knee frontal plane moment.

Results

Males in the VIS group showed a larger vertical ground reaction force (S1: 25.4 ± 3.1 N/kg, S2: 25.8 ± 2.9 N/kg, S3: 25.2 ± 3.2 N/kg) and knee flexion moments (S1: ?3.8 ± 0.9 Nm/kg, S2: ?4.0 ± 1.2 Nm/kg, S3: ?3.9 ± 1.3 Nm/kg) compared to the males in the VER and CTRL groups and to the females in the VIS group (p < 0.05). Additionally, the males in the VIS group reduced knee valgus moment and the females in the VER group reduced knee varus moment over time (n.s.).

Conclusion

Male subjects clearly benefit from visual feedback. Females may need different feedback modes to learn a correct movement pattern. Sex-specific learning preferences may have to be acknowledged in day by day practice. Adding video instruction or feedback to regular training regimens when teaching athletes safe movement patterns and providing individual feedback might target suboptimal long-term results and optimize ACL injury prevention programmes.

Level of evidence

I.

     

A prevention strategy to reduce the incidence of injury in high school basketball: a cluster randomized controlled trial.

OBJECTIVE: To examine the effectiveness of a sport-specific balance training program in reducing injury in adolescent basketball. DESIGN: Cluster randomized controlled trial. SETTING: Twenty-five high schools in Calgary and surrounding area. SUBJECTS: Nine hundred and twenty high school basketball players (ages 12-18). INTERVENTION: Subjects were randomly allocated by school to the control (n = 426) and training group (n = 494). Both groups were taught a standardized warm-up program. The training group was also taught an additional warm-up component and a home-based balance training program using a wobble board. MAIN OUTCOME MEASURES: All injuries occurring during basketball that required medical attention and/or caused a player to be removed from that current session and/or miss a subsequent session were then recorded and assessed by a team therapist who was blinded to training group allocation. RESULTS: A basketball-specific balance training program was protective of acute-onset injuries in high school basketball [RR = 0.71 (95% CI; 0.5-0.99)]. The protective effect found with respect to all injury [RR = 0.8 (95% CI; 0.57-1.11)], lower-extremity injury [RR = 0.83 (95% CI; 0.57-1.19)], and ankle sprain injury [RR = 0.71 (95% CI; 0.45-1.13)] were not statistically significant. Self-reported compliance to the intended home-based training program was poor (298/494 or 60.3%). CONCLUSIONS: A basketball-specific balance training program was effective in reducing acute-onset injuries in high school basketball. There was also a clinically relevant trend found with respect to the reduction of all, lower-extremity, and ankle sprain injury. Future research should include further development of neuromuscular prevention strategies in addition to further evaluation of methods to increase compliance to an injury-prevention training program in adolescents.     

A 6-week warm-up injury prevention programme results in minimal biomechanical changes during jump landings: a randomized controlled trial

Purpose

To examine the extent to which an ACL injury prevention programme modifies lower extremity biomechanics during single- and double-leg landing tasks in both the sagittal and frontal plane. It was hypothesized that the training programme would elicit improvements in lower extremity biomechanics, but that these improvements would be greater during a double-leg sagittal plane landing task than tasks performed on a single leg or in the frontal plane.

Methods

Ninety-seven competitive multi-directional sport athletes that competed at the middle- or high-school level were cluster randomized into intervention (n?=?48, age?=?15.4?±?1.0 years, height?=?1.7?±?0.07 m, mass?=?59.9?±?11.0 kg) and control (n?=?49, age?=?15.7?±?1.6 years, height?=?1.7?±?0.06 m, mass?=?60.4?±?7.7 kg) groups. The intervention group participated in an established 6-week warm-up-based ACL injury prevention programme. Three-dimensional biomechanical analyses of a double- (SAG-DL) and single-leg (SAG-SL) sagittal, and double- (FRONT-DL) and single-leg (FRONT-SL) frontal plane jump landing tasks were tested before and after the intervention. Peak angles, excursions, and external joint moments were analysed for group differences using 2 (group)?×?4 (task) repeated measures MANOVA models of delta scores (post–pre-test value) (α?<?0.05).

Results

Relative to the control group, no significant biomechanical changes were identified in the intervention group for any of the tasks (n.s.). However, a group by task interaction was identified for knee abduction (λ?=?0.80, p?=?0.02), such that participants in the intervention group showed relative decreases in knee abduction moments during the SAG-DL compared to the SAG-SL (p?=?0.005; d?=?0.45, CI?=?0.04–0.85) task.

Conclusion

A 6-week warm-up-based ACL injury prevention programme resulted in no significant biomechanical changes during a variety of multi-directional jump landings. Clinically, future prevention programmes should provide a greater training stimulus (intensity, volume), more specificity to tasks associated with the mechanism of ACL injury (single-leg, non-sagittal plane jump landings), and longer programme duration (>?6 weeks) to elicit meaningful biomechanical changes.

Level of evidence

I.

     

Exercise-based injury prevention for community-level adolescent cricket pace bowlers: A cluster-randomised controlled trial

ObjectivesTo investigate if an exercise-based injury prevention program (IPP) can modify risk factors for injury in community-level adolescent cricket pace bowlers.DesignCluster-randomised controlled trial.MethodsEight cricket organisations (training two times per week and no previous involvement in a structured IPP) participated in this cluster-randomised trial. Participants were aged 14–17 years, injury free, and not currently performing a rehabilitation/exercise program. Cricket organisations (clusters) were block-randomised by computerised number generation into an intervention group (performed an eight-week IPP at training) or control group (continued their usual cricket activity). Participants were not blinded to group allocation. Strength, endurance, and neuromuscular control were assessed at baseline and follow-up. Treatment effects were estimated using linear mixed models.ResultsSixty-five male adolescent pace bowlers (intervention n = 32 and control n = 33) were randomised. There were significant treatment effects favouring the intervention group for shoulder strength (90°/s) 0.05 (95% CI 0.02–0.09) N m/kg, hamstring strength (60°/s) 0.32 (95% CI 0.13–0.50) N m/kg, hip adductor strength dominant 0.40 (95% CI 0.26–0.55) N m/kg and non-dominant 0.33 (95% CI 0.20–0.47) N m/kg, SEBT reach distance dominant 3.80 (95% CI 1.63–6.04) percent of leg length (%LL) and non-dominant 3.60 (95% CI 1.43–5.78) %LL, and back endurance 20.4 (95% CI 4.80–36.0) seconds. No differences were observed for shoulder strength (180°/s) (p = 0.09), hamstring strength (180°/s) (p = 0.07), lumbopelvic stability (p = 0.90), and single leg squat knee valgus angle (dominant p = 0.06, non-dominant p = 0.15).ConclusionsExercise-based IPPs can modify risk factors for injury in community-level adolescent pace bowlers. Future research is needed to confirm if IPPs can also reduce injury risk in this population.     

The effects of preexercise stretching on muscular soreness, tenderness and force loss following heavy eccentric exercise

The present study sought to investigate the effects of preexercise stretching on delayed onset muscle soreness (DOMS), i.e. soreness, tenderness and loss of muscle force, that usually occurs after strenuous or unaccustomed eccentric exercise. Ten female volunteers performed 10 sets of 10 maximal isokinetic eccentric contractions for knee flexion with both legs after a 5-min ergometer cycling warm-up. Prior to the exercise for one leg, randomly chosen, 4 x 20 s of static stretching for the hamstring muscle group was implemented. Rated soreness, tenderness on algometer pressure and loss of maximal eccentric contractile force was evaluated preexercise and 24, 48 and 96 h postexercise. The exercise bout produced severe DOMS, with parameters peaking and troughing at 48 h postexercise. However, no significant differences were found, regarding any of the parameters, when comparing stretched and nonstretched legs. The present study thus suggests that preexercise static stretching has no preventive effect on the muscular soreness, tenderness and force loss that follows heavy eccentric exercise.     

A systematic review into the efficacy of static stretching as part of a warm-up for the prevention of exercise-related injury

A systematic review of the literature was undertaken to assess the efficacy of static stretching as part of the warm-up for the prevention of exercise-related injuries. Computer-aided literature search for articles post-1990 and pre-January 2008 related to static stretching and injury prevention using MEDLINE, SPORT Discus, PubMed, and ScienceDirect databases. All relevant randomised clinical trials (RCTs) and controlled clinical trials (CCTs) satisfying inclusion/exclusion criteria were evaluated by methodological assessment to score the studies using accredited criteria. Seven out of 364 studies met the inclusion/exclusion criteria. All four RCTs concluded that static stretching was ineffective in reducing the incidence of exercise-related injury, and only one of the three CCTs concluded that static stretching did reduce the incidence of exercise-related injury. Three out of the seven studies noted significant reductions in musculotendinous and ligament injuries following a static stretching protocol despite nonsignificant reductions in the all-injury risk. All RCTs scored over 50 points (maximum possible score = 100), whereas all CCTs scored under 45 points. There is moderate to strong evidence that routine application of static stretching does not reduce overall injury rates. There is preliminary evidence, however, that static stretching may reduce musculotendinous injuries.     

A randomized controlled trial for the effect of passive stretching on measures of hamstring extensibility, passive stiffness, strength, and stretch tolerance

To measure hamstring extensibility, stiffness, stretch tolerance, and strength following a 4-week passive stretching program. Randomized controlled trial. Twenty-two healthy participants were randomly assigned to either a 4-week stretching program consisting of 4 hamstring and hip stretches performed 5 times per week, or a non-stretching control group. Hamstring extensibility and stiffness were measured before and after training using the instrumented straight leg raise test (iSLR). Stretch tolerance was measured as the pain intensity (visual analog scale; VAS) elicited during the maximal stretch. Hamstring strength was measured using isokinetic dynamometry at 30 and 120° s⁻¹. Hamstring extensibility increased by 20.9% in the intervention group following 4 weeks of training (p < 0.001; d = 0.86). Passive stiffness was reduced by 31% in the intervention group (p < 0.05; d = −0.89). Stretch tolerance VAS scores were not different between groups at either time point, and no changes were observed following training. There were no changes in hamstring concentric strength measured at 30 and 120° s⁻¹. Passive stretching increases hamstring extensibility and decreases passive stiffness, with no change in stretch tolerance defined by pain intensity during the stretch. Compared to previous research, the volume of stretching was higher in this study. The volume of prescribed stretching is important for eliciting the strong clinical effect observed in this study.     

To stretch or not to stretch: the role of stretching in injury prevention and performance

Stretching is commonly practiced before sports participation; however, effects on subsequent performance and injury prevention are not well understood. There is an abundance of literature demonstrating that a single bout of stretching acutely impairs muscle strength, with a lesser effect on power. The extent to which these effects are apparent when stretching is combined with other aspects of a pre‐participation warm‐up, such as practice drills and low intensity dynamic exercises, is not known. With respect to the effect of pre‐participation stretching on injury prevention a limited number of studies of varying quality have shown mixed results. A general consensus is that stretching in addition to warm‐up does not affect the incidence of overuse injuries. There is evidence that pre‐participation stretching reduces the incidence of muscle strains but there is clearly a need for further work. Future prospective randomized studies should use stretching interventions that are effective at decreasing passive resistance to stretch and assess effects on subsequent injury incidence in sports with a high prevalence of muscle strains.     

Effect of static stretching on prevention of injuries for military recruits

This prospective study was designed to evaluate whether static stretching can prevent training-related injuries in Japan Ground Self-Defense Force military recruits. A total of 901 recruits between 1996 and 1998 were divided into two groups. Of which, 518 recruits were assigned to the stretching group and practiced static stretching before and after each physical training session. The control subjects (383 recruits in the nonstretching group) did not stretch statically prior to exercise. The static stretching consisted of 18 exercises. We collected injury data from medical records and assessed the incidence and the location of injury. The total injury rate was almost the same between two groups; however, the incidences of muscle/tendon injury and low back pain were significantly lower in the stretching group (p < 0.05). Static stretching decreased the incidence of muscle-related injuries but did not prevent bone or joint injuries.     

关节镜下治疗半月板损伤的临床随机对照研究

目的比较关节镜切除与射频技术治疗半月板损伤的临床疗效。方法采用随机、对照的临床试验方法,对照组64例采用关节镜下切除法,治疗组64例采用关节镜下射频汽化技术治疗。结果两组患者术后Lysholm评分较术前明显提高,差异有统计学意义(P<0.01);而两组间差异无统计学意义(P>0.05)。两组优良率、手术时间、术后2周内关节积液及并发症比较差异均无统计学意义(P>0.05)。结论射频技术治疗半月板损伤疗效显著,是目前值得推广的一种治疗方法。     

Exercise program for prevention of groin pain in football players: a cluster‐randomized trial

Groin injuries cause major problems in sports and particularly in football. Exercise is effective in treating adductor‐related groin pain, but no trials have been published regarding the specific prevention of groin pain or prevention specifically targeting overuse injuries in sport using exercise programs. We performed a cluster‐randomized trial including 55 football clubs representing 1211 players. The clubs were randomized to an exercise program aimed at preventing groin injuries (n=27) or to a control group training as usual (n=28). The intervention program consisted of six exercises including strengthening (concentric and eccentric), coordination, and core stability exercises for the muscles related to the pelvis. Physiotherapists assigned to each club registered all groin injuries. Twenty‐two clubs in each group completed the study, represented by 977 players. There was no significant effect of the intervention (HR=0.69, 95% CI 0.40–1.19). The risk of a groin injury was reduced by 31%, but this reduction was not significant. A univariate analysis showed that having had a previous groin injury almost doubles the risk of developing a new groin injury and playing at a higher level almost triples the risk of developing a groin injury.     

Modifying bowling kinematics in cricket pace bowlers with exercise-based injury prevention: A cluster-randomised controlled trial

ObjectivesUndesirable bowling kinematics can increase the risk of low back injury. This study investigated if an exercise-based injury prevention program (IPP) could modify bowling kinematics in community-level adolescent pace bowlers.DesignCluster-randomised controlled trial.MethodsPace bowlers from eight cricket organisations were cluster-randomised into an intervention or control group. At baseline and follow-up sessions biomechanical bowling data were collected. Between sessions, the intervention group completed an eight-week IPP while the control continued their normal cricket activity. Treatment effects (95% CI) were estimated with linear mixed models.ResultsThere were significant treatment effects favouring the intervention group for shoulder counter-rotation (−3.8°; −7.2° to −0.3°) and lateral trunk flexion relative to the pelvis (−2.2°; −4.0° to −0.5°). Shoulder counter-rotation also increased in the control group by 2.2° (Cohen’s d = 0.22). There were no effects of the intervention on: lateral trunk flexion at front foot contact (FFC) (1.2°; −2.5° to 4.8°), lateral trunk flexion at ball release (BR) (−0.5°; −3.0° to 2.0°), pelvis rotation at FFC (0.9°; −4.0° to 2.2°), pelvis rotation at BR (−1.1°; −5.7° to 3.6°), front hip angle at FFC (1.6°; −3.6° to 6.7°), front hip angle at BR (−1.6°; −5.0° to 1.9°), front knee angle at FFC (−1.1°; −4.5° to 2.3°), front knee angle at BR (1.7°; −5.6° to 9.1°), or ball velocity (1.1 km h⁻¹; −7.5 km h⁻¹ to 9.7 km h⁻¹).ConclusionsThe IPP maintained shoulder counter-rotation and lateral trunk flexion relative to the pelvis in the intervention group and this could attenuate injury risk. No treatment effects were observed for lower-limb kinematics.