Nordic Hamstring Exercise Research Articles

Sprinting, Strength, and Architectural Adaptations Following Hamstring Training in Australian Footballers.

The aim of this study was to determine the sprinting, strength, and architectural adaptations following a hip-dominant flywheel (FLY) or Nordic hamstring exercise (NHE) intervention in Australian footballers. Twenty-seven male athletes were randomized to FLY (n=13) or NHE (n=14) training across a 39-week period (inclusive of pre-season and in-season). Biceps femoris long head (BFlh) architecture was assessed throughout. Eccentric hamstring strength and 40m sprint times (with force-velocity profiling) were assessed at baseline, end of pre-season, and following the intervention. After the intervention, BFlh fascicle length was longer in both groups compared to baseline (FLY: 1.16cm, 95%CI: 0.66 to 1.66cm, d=1.99, p<0.001; NHE: 1.08cm, 95%CI: 95%CI 0.54 to 1.61cm, d=1.73, p<0.001). Both groups also increased their eccentric strength (FLY: mean change 82N, 95%CI 12 to 152N, d=1.34, p=0.026; NHE: mean change 97N, 95%CI 47 to 146N, d=1.77, p=0.001). After pre-season, the NHE group improved their 5m sprint time by 3.5% (±1.2%) and were 3.7% (±1.4%) and 2.0% (±0.5%) faster than the FLY group across 5m and 10m, respectively. At the end of pre-season, the FLY group improved maximal velocity by 3.4% (±1.4%) and improved horizontal force production by 9.7% in-season (±2.2%). Both a FLY and NHE intervention increase BFlh fascicle length and eccentric strength in Australian Footballers. An NHE intervention led to enhanced acceleration capacity. A FLY intervention was suggested to improve maximal sprint velocity and horizontal force production, without changes in sprint times. These findings have implications for hamstring injury prevention but also programs aimed at improving sprint performance.

Characterization of Injuries in Male and Female Ultimate Frisbee Players at the Elite Club-Level.

BackgroundUltimate Frisbee is a rapidly growing sport played in all levels of competition in men’s, women’s, and coed divisions. Despite widespread popularity, there remains a lack of research on injury risk and prevalence during a season.PurposeTo determine the prevalence of injuries among elite club-level men and women Ultimate Frisbee players and to identify elements associated with injury during a single season.Study DesignDescriptive epidemiological study.MethodsVoluntary preseason and postseason online surveys were distributed to local elite club-level Ultimate teams in 2019. Surveys assessed players’ lifetime Ultimate-associated injury history, injury status, training regimen, and other related elements.ResultsFifty-seven and 84 players were eligible to complete the preseason and postseason surveys, respectively. Prior to the 2019 season, 97% of female respondents and 100% of male respondents reported a previous Ultimate-related injury in their career, with all reporting a prior lower extremity injury. During the 2019 season, 56% of respondents reported being injured, and 12% missed one month or more of the season, with 88% of injured players reporting a lower extremity injury. Men reported more ankle and calf injuries than women, and there was a strong negative correlation between time missed due to injury during the 2018 season and the number of days per week spent weight-training and accumulated training.ConclusionThere is a high prevalence of lower extremity injury among elite club-level Ultimate players during a single season and pervasive lower extremity injury history may contribute to high injury prevalence. Observed injury patterns suggest targeted interventions including Nordic Hamstring Exercises and balance and proprioceptive training may decrease injury risk. Further research into this topic is needed to help reduce injury in these athletes.Levels of EvidenceLevel 3.

A Preseason Training Program With the Nordic Hamstring Exercise Increases Eccentric Knee Flexor Strength and Fascicle Length in Professional Female Soccer Players.

BackgroundTraining programs that include the Nordic hamstring exercise (NHE) have been shown to increase eccentric knee flexor strength and biceps femoris fascicle length in male athletes. However, the effect of NHE on female athletes remains unknown.PurposeTo investigate the collective and individual responses of professional female soccer players engaged in a preseason training program with the NHE regarding eccentric knee flexor strength and biceps femoris long head fascicle length.Study DesignQuasi-experimental study.MethodsSixteen amateur female soccer players (without a NHE training routine) were evaluated 8-weeks apart to: (1) assess reliability of eccentric knee flexor strength and biceps femoris fascicle length measures; and (2) determine the typical error of measures that would be used to discriminate training responders and non-responders. The NHE training group had 17 professional female soccer players who performed an 8-week training program with the NHE during preseason. Within-group analysis was performed with paired sample t-tests (pre- vs. post-training), and individual responses were determined using the typical error criteria.ResultsThe non-trained group’s data demonstrated that measures of strength (ICC=0.82-0.87, typical error = 12-13 N) and fascicle length (ICC=0.92-0.97; typical error = 0.19-0.38 cm) were reliable. In the NHE training group, both limbs increased the eccentric knee flexor strength (~13%; ES=0.74-0.82) and the biceps femoris fascicle length (~6%; ES=0.44-0.65). Twelve players (~71%) were considered responders to the NHE training program for the eccentric knee flexor strength, while eight athletes (~47%) were responders for the biceps femoris fascicle length.ConclusionThe 8-week preseason training program with the NHE increased both eccentric knee flexor strength and biceps femoris fascicle length in professional female soccer players. More than two-thirds of players demonstrated a meaningful increase in eccentric strength, while nearly half achieved consistent fascicle length increases with the NHE training.

The uptake of the Nordic hamstring exercise programme as an injury prevention strategy in professional cricket in the United Kingdom and barriers to implementation

ObjectivesTo report hamstring prevention strategies of professional male cricket clubs in the United Kingdom, identify the application of the Nordic hamstring programme (NHP) and gain knowledge of medical teams’ reasons for the NHP’s inclusion or exclusion. DesignCross-sectional questionnaire. SettingOnline survey. Participants15 (75%) of professional cricket clubs in the United Kingdom. Main outcome measuresSurvey based on the RE-AIM framework. ResultsTwelve clubs reported having a formal hamstring injury prevention programme. The Nordic hamstring exercise and eccentric exercises (100%) were the most used interventions. Three clubs implemented the NHP, with one classed as fully compliant. Respondents partially agreed, on a 5 point Likert scale, that the Nordic hamstring exercise was effective at reducing injuries at their club (Mean 3.73 ± SD 0.70) and across professional cricket (3.87 ± 0.64). Barriers to implementation across cricket included players not positively perceiving the programme (60%) with a cultural change required (60%) for its adoption. ConclusionsThe Nordic hamstring exercise is positively received by medical personnel in professional cricket in conjunction with other prevention strategies. Three clubs have utilised the NHP in the last three seasons with one club considered fully compliant. A cultural shift from players and coaches may be required for successful NHP implementation.

Assisted or unassisted Nordic Hamstring Exercise? — Resistance exercise determinants at a glance

ABSTRACT The Nordic Hamstring Exercise (NHE) effectively strengthens the knee flexors. Typically conducted without assistance, extended knee angles are not reached with sustained muscle activation in the presence of insufficient eccentric strength and/or fatigue. This might impair the desired neuromuscular adaptations and assessment accuracy. This study investigated kinetic and kinematic differences between assisted and unassisted NHEs (3 × 3 repetitions) performed by sixteen male sprinters (22 years, 181 cm, 76 kg). Kinetic (peak moment, impulse) and kinematic parameters (e.g., time under tension, range of motion to excessive downward acceleration (ROMDWA) were investigated. All analysed parameters significantly differed between assisted and unassisted NHEs (p ≤ 0.003; 0.635≤ ηp² ≤ 0.929) favouring assisted execution, except for peak moments and maximal hip flexion. Repetition 1 of assisted NHEs revealed 21% higher impulses rising to 82% during repetition 9. Equivalent interactions of mode and repetition became apparent for time under tension, ROMDWA, mean and fractional angular velocity. Unassisted NHEs elicited substantially greater inter-repetition fatigue (rep1 vs. rep9): +79% fractional angular velocity (d = 1.01), −41% impulse (d = 1.53), −31% ROMDWA (d = 0.99) and −29% time under tension (d = 1.45). Assisted NHEs ensured higher execution quality and lower between-participant variability by facilitating a controlled full-ROM movement. Three sets of 3 NHEs sufficed to induce substantial fatigue within and across sets.

Biceps Femoris Muscle is Activated by Performing Nordic Hamstring Exercise at a Shallow Knee Flexion Angle.

The semitendinosus (ST) muscle is primarily used during Nordic hamstring exercise (NHE), which is often prescribed for preventing hamstring injury, though the biceps femoris long head (BFlh) muscle that is more susceptible to injuries. Thus, this study aimed to identify the modulation of BFlh muscle activity with different knee flexion angles during NHE using an inclined platform. Fourteen male athletes performed NHE and maintained their position at maximum inclination (NH). Subjects also performed isometric NHE using a platform inclined to 50° (ICL) and 40° (ICH), and the knee flexion angle was controlled to 50° and 30°. The electromyography (EMG) activity of the BFlh, ST, semimembranosus, gluteus maximus, elector spinae, and rectus abdominus muscles was determined during each exercise. The EMG of the ST was higher than that of the BFlh during NHE and the highest of all muscles in all exercises (p < 0.05). Moreover, the activity of the BFlh tended to be higher than that of the ST for ICH than for ICL, regardless of the knee joint angle. The activity of the BFlh becomes equivalent to that of the ST during NHE at a knee flexion angle of less than 50°. These results indicate that performing NHE at a shallow knee flexion angle will enhance the activity of the BFlh muscle.

The Relationship Between the Contact Force at the Ankle Hook and the Hamstring Muscle Force During the Nordic Hamstring Exercise.

A novel device has been developed to assess eccentric hamstring strength during the Nordic hamstring exercise (NHE) by measuring the contact force at the ankle hook (brace). The purpose of this study was to determine the correlation between the force measured at the ankle hook and the hamstring force estimated by a low extremity model. Thirteen male college sprinters were recruited to perform NHE on an instrumented device Nordbord (Vald Performance, Australia). Contact forces were measured at a sampling rate of 50 Hz at the hooks using the uniaxial load cells. 3D kinematics were measured simultaneously at a sampling rate of 200 Hz using a 16-camera motion analysis system (Vicon Motion Analysis, Oxford, United Kingdom) during the NHE. The data were processed with Visual 3D (C-Motion, Germantown, MD, United States) and OpenSim (NCSRR, Stanford, CA, United States) to calculate the knee joint center’s coordinates and hamstring moment arms during NHE. A static low extremity model was built to estimate the hamstring force during NHE. We have observed a significant but not very high correlation (r2 = 0.58) between peak hamstring force and the peak contact force at the ankle hook. The peak contact force measured at the ankle hook can only explain a little more than half of the variations in peak hamstring muscle forces during NHE. Caution must be exercised when assessing the eccentric hamstring strength using the ankle contact force during NHE.

Individual differences in the distribution of activation among the hamstring muscle heads during stiff-leg Deadlift and Nordic hamstring exercises

ABSTRACT The aim of this study was to compare the distribution of activation among the three heads of the hamstring between a knee flexion-oriented exercise (Nordic hamstring) and a hip extension-oriented exercise (stiff-leg Deadlift) at the group and individual level. Data were collected for 20 participants. Muscle activation of the semimembranosus (SM), semitendinosus (ST), and biceps femoris (BF) was estimated using surface electromyography (EMG) during Nordic hamstring and stiff-leg Deadlift exercises. Although Nordic hamstring exercise induced a higher normalized RMS EMG value for BF (64.5 ± 17.4%) compared to SM (48.6 ± 14.6%; P 0.001) and ST (55.9 ± 17.4%; P < 0.001), the greatest active muscle varied between individuals. Similar interindividual differences in the greatest active muscle were found for the stiff-leg Deadlift exercise. Regarding the distribution of activation, the stiff-leg Deadlift favoured the contribution of the SM compared to ST (P < 0.001, 18/20 participants) whereas the Nordic hamstring exercise favoured the contribution of the ST compared to SM (P < 0.001, 19/20 participants). Importantly, these tasks affected the contribution of the activation of BF in different ways between individuals. The distribution of activation across the three muscles was well correlated between the two exercises (r values 0.42).

Effect of Different Slopes of the Lower Leg during the Nordic Hamstring Exercise on Hamstring Electromyography Activity.

The purpose of this study was to examine whether the NHE with an increased lower leg slope angle would enhance hamstring EMG activity in the final phase of the descend. The hamstring EMG activity was measured, the biceps femoris long head (BFlh) and the semitendinosus (ST). Fifteen male volunteers participated in this study. Subjects performed a prone leg curl with maximal voluntary isometric contraction to normalize the hamstring EMG activity. Subsequently, subjects performed the NHE, with the help of a certified strength and conditioning specialist, while the lower leg slope angle were randomly set at 0° (NH), 20° (N20), and 40° (N40). To compare hamstring EMG activity during the NHE variations, the knee flexion angle was set in the range from 0° to 50°, divided into five phases (0-10°, 10-20°, 20-30°, 30-40° and 40-50°), where 0° indicated that the knee was fully extended. To calculate the knee extension angular velocity, the knee flexion angle divided by time, and break point angle (BPA) was the angle at which 10°/s was exceeded. In the statistical analysis, a two-way repeated measures ANOVA was used for the hamstring EMG activity and a one-way repeated measures ANOVA was used for the BPA. The EMG activity of the BFlh and the ST in N20 and N40 was significantly higher than in NH at knee flexion angle of 0-20° (p < 0.05). For the BPA, NH (57.75° ± 13.28°), N20 (36.27° ± 9.89°) and N40 (16.26° ± 9.58°) were significantly higher in that order (p < 0.05). The results of this study revealed that the NHE with an increased lower leg slope angle shifted the BPA to the lower knee flexion angle and enhanced the hamstring EMG activity in the final phase of the descent.

Development of a Novel Nordic Hamstring Exercise Device to Measure and Modify the Knee Flexors' Torque-Length Relationship.

The Nordic hamstring exercise (NHE) has been shown to reduce hamstring injury risk when employed in training programs. This study investigates a novel device to modify the NHE torque-length relationship of the knee flexors, as targeting the hamstrings at a more extended length may have benefits for hamstring strain injury prevention and rehabilitation. Eighteen recreational male participants completed three bilateral NHE repetitions at a conventional 0° flat position, a 10° incline, and a 10° decline slope on a novel device (HALHAM°). Measures of peak torque and break-torque angle explored the effect of inclination on the knee flexors' length-tension relationship. Relative thigh-to-trunk angle and angular velocity of the knee joint were used to assess influence of inclination on technique and exercise quality. Break-torque angle increased when performed at an incline (134.1 ± 8.6°) compared to both the decline (112.1 ± 8.3°, p <0.0001, g = 2.599) and standard flat NHE positions (126.0 ± 9.8°, p = 0.0002, g = 0.885). Despite this, altering inclination did not affect eccentric knee flexor peak torque (decline = 132.0 ± 63.1 Nm, flat = 149.7 ± 70.1 Nm, incline = 148.9 ± 64.9 Nm, F = 0.952, p = 0.389), angular velocity of the knee joint at break-torque angle (decline = 23.8 ± 14.4°, flat = 29.2 ± 22.6°, incline = 24.5 ± 22.6°, F = 0.880, p = 0.418) or relative thigh-to-trunk angle at break-torque angle (decline = 20.4 ± 10.4°, flat = 16.7 ± 10.8°, incline = 20.2 ± 11.2°, F = 1.597, p = 0.207). The report recommends the use of arbitrary metrics such as break-torque angle that can be replicated practically in the field by practitioners to assess proxy muscle length changes i.e., the angular range over which the torque can be produced. Inclination of the Nordic hamstring exercise leads to hamstring muscle failure at longer muscle lengths without reductions in the maximal force exuded by the muscle. Therefore, the NHE performed on an incline may be a more effective training intervention, specific to the proposed mechanism of hamstring strain injury during sprinting that occurs whilst the muscle is rapidly lengthening. Using a graded training intervention through the inclinations could aid gradual return-to-play rehabilitation.

Combining the Copenhagen Adduction Exercise and Nordic Hamstring Exercise Improves Dynamic Balance Among Male Athletes: A Randomized Controlled Trial.

Copenhagen adduction exercise (CAE) and Nordic hamstring exercise (NHE) reduce the incidence of groin and hamstring injuries. Efficient dynamic balance can improve motor performance and reduce the risk of injuries in athletes. However, the effects of these exercises on dynamic balance have not been investigated. CAE and NHE, as well as a combination of both exercises, would improve dynamic balance among amateur male athletes. Randomized controlled trial. Level 1. A total of 200 male athletes aged 21.9 ± 2.4 years were included in the study and randomly assigned to 4 groups: CAE group (n = 50), NHE group (n = 50), CAE and NHE group (n = 50), and a control group (n = 50). A total of 177 male athletes completed the study. The primary outcome measure was the limit of stability (LoS), which was measured using the Biodex Stability System to assess the performance of the dynamic balance. The LoS of the athletes' performance was measured pre- and postintervention after 6 weeks. The LoS significantly improved in all treatment groups, including CAE (44.5% ± 5.3%), NHE (43.2% ± 5.3%), and CAE + NHE (48.4% ± 5.1%) groups when compared with the control group (28.3% ± 4.8%) after 6 weeks (all Ps < 0.01). The improvement of LoS was significantly greater in the CAE + NHE group compared with other groups (CAE, NHE, and control groups). There was a significant increase in dynamic balance performance postintervention among male athletes. CAE and NHE may improve injury prevention programs. The results of this study provide evidence for athlete trainers and coaches to consider including the CAE and NHE as components of injury prevention programs to improve balance capacity and performance in athletes. Such improvements in balance may prevent injury risk and decrease absenteeism and injury-related financial burdens.

A prospective study of risk factors for hamstring injury in Australian football league players

ABSTRACT This study aimed to explore the association between hamstring strength, age and lower limb soft tissue injury history and subsequent hamstring injury among Australian Football League (AFL) players. This prospective cohort study recruited 125 players from three professional AFL teams. Eccentric knee flexor strength was assessed while performing the Nordic hamstring exercise in pre-season, and injury data were collected retrospectively (hamstring, groin, calf, quadriceps and knee), and prospectively (hamstring injuries) for one AFL playing season. Fourteen players (11%) sustained a hamstring injury in the subsequent playing season. Nordic strength was not significantly associated with future hamstring injury (Odds Ratio (OR) 1.9, p = 0.36), whereas player age greater than 25 years (OR = 2.9, p < 0.05), report of a hamstring injury within the previous year (OR = 3.7, p = 0.01), or greater than 1-year (OR = 3.6, p = 0.01), a previous groin (OR = 8.6, p < 0.01) or calf injury (OR = 4.6, p = 0.01) were factors significantly associated with subsequent hamstring injury. Based on these findings, increasing age and previous hamstring, groin and calf injury are all associated with an elevated risk of subsequent hamstring injury in AFL players.

Implementing Strength Training Strategies for Injury Prevention in Soccer: Scientific Rationale and Methodological Recommendations.

Due to the negative effects that injuries have on performance, club finances, and long-term player health (permanent disability after a severe injury), prevention strategies are an essential part of both sports medicine and performance. Purpose: To summarize the current evidence regarding strength training for injury prevention in soccer and to inform its evidence-based implementation in research and applied settings. Conclusions: The contemporary literature suggests that strength training, proposed as traditional resistance, eccentric, and flywheel training, may be a valid method to reduce injury risk in soccer players. Training strategies involving multiple components (eg,a combination of strength, balance, plyometrics) that include strength exercises are effective at reducing noncontact injuries in female soccer players. In addition, the body of research currently published supports the use of eccentric training in sports, which offers unique physiological responses compared with other resistance exercise modalities. It seems that the Nordic hamstring exercise, in particular, is a viable option for the reduction of hamstring injuries in soccer players. Moreover, flywheel training has specific training peculiarities and advantages that are related to the combination of both concentric and eccentric contraction, which may play an important role in injury prevention. It is the authors' opinion that strength and conditioning coaches should integrate the strength training methods proposed here in their weekly training routine to reduce the likelihood of injuries in their players; however, further research is needed to verify the advantages and disadvantages of these training methods to injury prevention using specific cohorts of soccer players.

Nordic Hamstring Exercise training induces improved lower-limb swing phase mechanics and sustained strength preservation in sprinters.

Nordic Hamstring Exercise (NHE) training improves eccentric hamstring strength and sprint performance. However, detraining causes rapid reductions of achieved adaptations. Furthermore, the transfer of improved hamstring capacity to swing phase mechanics of sprints is unknown. This longitudinal study aimed (a) to quantify NHE-induced adaptations by camera-based isokinetic assessments and sprint analyses, (b) to relate the magnitude of adaptations to the participants' initial performance level, (c) to investigate the transferability to sprints, and (4) to determine strength preservations after 3months. Twelve sprinters (21years, 1.81m, 74kg) were analyzed throughout 22weeks. They performed maximal sprints and eccentric knee flexor and concentric knee extensor tests before and after a 4-week NHE training. Sprints and isokinetic tests were captured by ten and four high-speed cameras. The dynamic control ratio at the equilibrium point (DCRe) evaluated thigh muscle balance. High-intensity NHE training elicited significant improvements of hamstring function (P range: <.001-.011, d range: 0.44-1.14), thigh muscle balance (P<0.001, d range: 0.80-1.08) and hamstring-related parameters of swing phase mechanics (P range: <0.001-0.022, d range: 0.12-0.57). Sprint velocity demonstrated small increases (+1.4%, P<0.001, d=0.26). Adaptations of hamstring function and thigh muscle balance revealed moderate to strong transfers to improved sprint mechanics (P range: <0.001-0.048, R2 range: 34%-83%). The weakest participants demonstrated the highest adaptations of isokinetic parameters (P range: 0.003-0.023, R2 range: 42%-62%), whereas sprint mechanics showed no effect of initial performance level. Three months after the intervention, hamstring function (+6% to +14%) and thigh muscle balance (+8% to +10%) remained significantly enhanced (P<0.001, ƞp 2 range: 0.529-0.621). High-intensity NHE training induced sustained improved hamstring function of sprinters, which can be transferred to swing phase mechanics of maximal sprints. The initial performance level, NHE training procedures and periodization should be considered to optimize adaptations.

Sprint Specificity of Isolated Hamstring-Strengthening Exercises in Terms of Muscle Activity and Force Production.

To train hamstring muscle specifically to sprint, strengthening programs should target exercises associated with horizontal force production and high levels of hamstring activity. Therefore, the objectives of this study were to analyze the correlation between force production capacities during sprinting and hamstring strengthening exercises, and to compare hamstring muscle activity during sprinting and these exercises. Fourteen track and field regional level athletes performed two maximal 50-m sprints and six strengthening exercises: Nordic hamstring exercises without and with hip flexion, Upright-hip-extension in isometric and concentric modalities, Standing kick, and Slide-leg-bridge. The sprinting horizontal force production capacity at low (F0) and high (V0) speeds was computed from running velocity data. Hamstring muscle performances were assessed directly or indirectly during isolated exercises. Hamstring muscle electromyographic activity was recorded during all tasks. Our results demonstrate substantially large to very large correlations between V0 and performances in the Upright-hip-extension in isometric (rs = 0.56; p = 0.040), Nordic hamstring exercise without hip flexion (rs = 0.66; p = 0.012) and with 90° hip flexion (rs = 0.73; p = 0.003), and between F0 and Upright-hip-extension in isometric (rs = 0.60; p = 0.028) and the Nordic hamstring exercise without hip flexion (rs = 0.59; p = 0.030). However, none of the test exercises activated hamstring muscles more than an average of 60% of the maximal activation during top-speed sprinting. In conclusion, training programs aiming to be sprint-specific in terms of horizontal force production could include exercises such as the Upright-hip-extension and the Nordic hamstring exercise, in addition to maximal sprinting activity, which is the only exercise leading to high levels of hamstring muscle activity.

Different Interset Rest Intervals During the Nordic Hamstrings Exercise in Young Male Athletes.

The Nordic hamstring exercise (NHE) is known to reduce hamstrings injury risk in athletes. To optimize the NHE, it is important to understand how acute resistance-training variables influence its performance. To examine the effects of different interset rest intervals (ISRIs) on force indices during performance of the NHE. Crossover study. Laboratory. Ten well-trained, young, male, team-sport athletes (age = 20.7 ± 2.3 years, height = 179.4 ± 5.5 cm, mass = 83.9 ± 12.4 kg). Participants performed 2 sets of 6 repetitions of the NHE with either a 1- or 3-minute ISRI. All sets were performed using the NordBord. Peak force (newtons), average force (newtons), percentage maintenance, and percentage decline were recorded for both the dominant and nondominant limbs, and interlimb force asymmetries (percentages) were calculated. No interactions or main effects (P > .05) were present between conditions or sets for any variables. However, individual repetitions showed reductions (P< .05; effect size range = 0.58-1.28) in peak force from repetition 4 onward. Our findings suggest that a 1-minute ISRI was sufficient to maintain force-production qualities and interlimb asymmetries between sets during the NHE in well-trained athletes. Nonetheless, practitioners should be aware of the potentially large decrements in peak force production that may occur within the set.

Limited implementation of the Nordic hamstring exercise in professional and semi-professional soccer

Background/Purpose: In soccer players, non-contact injuries are most common, especially hamstring muscle injuries, which can be prevented by the Nordic hamstring exercise (NHE). This study assessed the professional and semi-professional soccer players and coaches’ awareness, implementation, and opinion of the NHE efficacy in reducing hamstring injuries. Methods: A questionnaire regarding the awareness, implementation, and opinions of the NHE’s efficacy in reducing hamstring muscle injuries was distributed. Results: The survey was completed by 812 (88.3% male and 11.7% female) players and coaches. Of these, 395 (48.6%) were aware of the NHE, and 355 (43.7%) implemented it in their current practice. Those implementing NHE had a positive opinion about its efficacy in reducing hamstring injuries. Conclusion: Further efforts and research are warranted to increase the international awareness and implementation of the NHE and educate soccer players and coaches about the importance of its implementation and effectiveness in preventing hamstring injury.

Influence of Lumbar Mobilizations During the Nordic Hamstring Exercise on Hamstring Measures of Knee Flexor Strength, Failure Point, and Muscle Activity: A Randomized Crossover Trial

ObjectiveThe aims of this study were to quantify the effects of spinal mobilization on force production, failure point, and muscle activity of the hamstrings during the Nordic hamstring exercise (NHE), and to explore individual differences in responses. MethodsIn a replicated randomized crossover trial, 24 asymptomatic, recreationally active men (age [mean ± standard deviation]: 27 ± 6 years; body mass: 82 ± 17 kg; height: 181 ± 8 cm) completed 2 standardized intervention trials (L4/5 zygapophyseal mobilizations) and 2 control trials. The failure point of the NHE was determined with 3D motion capture. Peak force, knee flexor torque, and electromyography (EMG) of the biceps femoris were measured. Data analyses were undertaken to quantify mean intervention response and explore any individual response heterogeneity. ResultsMean (95% confidence interval) left-limb force was higher in intervention than in control trials by 18.7 (4.6-32) N. Similarly, right-limb force was higher by 22.0 (3.4-40.6) N, left peak torque by 0.14 (0.06-0.22) N • m, and right peak torque by 0.14 (0.05-0.23) N • m/kg. Downward force angle was decreased in intervention vs control trials by 4.1° (0.5°-7.6°) on the side of application. Both peak EMG activity (P = .002), and EMG at the downward force (right; P = .020) increased in the intervention condition by 16.8 (7.1-26.4) and 8.8 (1.5-16.1) mV, respectively. Mean downward acceleration angle changed by only 0.3° (−8.9° to 9.4°) in intervention vs control trials. A clear response heterogeneity was indicated only for right force (Participant × Intervention interaction: P = .044; response heterogeneity standard deviation = 34.5 [5.7-48.4] N). Individual response heterogeneity was small for all other outcomes. ConclusionAfter spinal mobilization, immediate changes in bilateral hamstring force production and peak torque occurred during the NHE. The effect on the NHE failure point was unclear. Electromyographic activity increased on the ipsilateral side. Response heterogeneity was generally similar to the random trial-to-trial variability inherent in the measurement of the outcomes.

Post-match recovery of eccentric knee flexor strength in male professional football players

ObjectivesThis study aimed at verifying the effect of a football match on the eccentric knee flexor strength of male professional players along a 72-h period. Study designQuasi-experimental study. SettingFootball club facilities. ParticipantsFifteen players were assessed in four timepoints: 24 h before, immediately after, 48 h and 72 h after the match. Main outcome measuresThe eccentric knee flexor strength was assessed during the Nordic hamstring exercise execution. ResultsPlayers presented a significant strength reduction immediately after match (Δ = 12%; p = 0.001; large effect size, d = 1.10), and did not recover their strength capacity within a 48 h-period (Δ = 6%; p = 0.011; moderate effect size, d = 0.57). At 72 h after the match, strength was similar to baseline levels (Δ = 3.5%; p = 0.122; small effect size, d = 0.34). Secondarily, individual response analysis considered a player ‘fully recovered’ when his strength deficit compared to the baseline measure was lower than the measurement coefficient of variation (i.e., <5%). Only 6 (40%) and 9 (60%) players were ‘fully recovered’ at 48 h and 72 h after the match, respectively. ConclusionProfessional football players experienced an immediately post-match drop on the eccentric knee flexor strength, and significant strength deficits persisted for a 48-h period. Some players were not recovered at 72 h after the match.

The effect of pre-exercise Nordic hamstring exercise on hamstring neuromuscular response during soccer-specific activity

ABSTRACT Background: The Nordic hamstring exercise (NHE) has emerged as a popular intervention for improving eccentric hamstring strength, however recent literature suggests there is a potential for an increase in injury risk during subsequent exercise. Methods: To quantify the influence of pre-exercise NHE on the electromyographical response of the hamstrings, 10 male soccer players completed an experimental trial comprising 6 sets x 5 repetitions of NHE prior to the completion of a 45 minute soccer-specific protocol. Post-exercise NHE were performed in the experimental and control (no pre-exercise NHE) trials. Electromyographic (EMG) response (integrated, mean and peak amplitude) of the biceps femoris to the pre- and post-exercise NHE and the soccer-specific exercise protocol was quantified. Results: Integrated (P= 0.025) and mean (P= 0.020) EMG elicited a significant main effect for time in the soccer-specific protocol with higher values during the first 15 mins indicative of a fatigue effect. However, there was no trial x time interaction (P ≥ 0.78). There was no difference between trials in the EMG response to pre-exercise (P≥ 0.30) or post-exercise (P≥ 0.16) NHE trials. Conclusions: Therefore, although previous studies suggest performing pre-exercise NHE might impair maximal strength metrics, the current study’s results suggest that it does not impair the electromyographical response to subsequent soccer-specific exercise or NHE repetitions.