The Dose-Response of the Nordic Hamstring Exercise on Biceps Femoris Architecture and Eccentric Knee Flexor Strength: A Randomized Interventional Trial

The 11+ injury prevention programme decreases rate of hamstring strain injuries in male collegiate soccer players

OBJECTIVES

To investigate if the 11+ injury prevention programme decreases the risk of hamstring injury and improves recovery time and determine whether compliance with the 11+ affects hamstring injury risk.

METHODS

This study is a secondary analysis from a prospective cluster randomised controlled trial that included 65 National Collegiate Athletic Association (NCAA) division I and II men's soccer teams over the fall 2012 season. Thirty-one teams were randomised to the intervention group that were using the 11+ as their warm-up and 35 teams to the control group that continued to use their traditional warm-up. Each certified athletic trainer (ATC) collected data on demographics, hamstring injury (HSI), mechanism of injury, position, playing surface, time lost due to injury and compliance to the 11+ programme.

RESULTS

The 11+ decreased the risk of HSI by 63% compared with the control group (RR=0.37, 95% CI 0.21 to 0.63). Difference in return to play after HSI between the control (9.4±11.2 days) and intervention groups (10.2±11.3 days) was not significant (p=0.8). High compliance (>2 or more doses on average per week) reduced the risk of HSI by 78% (RR=0.22, 95% CI 0.06 to 0.87) compared with low compliance (<1 dose on average per week), and moderate compliance (1 to <2 doses on average per week) decreased the risk of HSI by 67% (RR=0.33, 95% CI 0.11 to 0.97) compared with low compliance. There was no significant difference between high and moderate compliance.

CONCLUSION

The 11+ decreased the risk of HSI by 63% but did not improve recovery time. High to moderate compliance is essential and makes the programme more effective at reducing HSI.

The relationship between hamstring strength tests and sprint performance in female Gaelic footballers: A correlation and linear regression analysis

OBJECTIVES

To investigate the relationships between handheld dynamometer (HHD), isokinetic and Nordic hamstrings exercise (NHE) measurements of knee flexor strength and their association with sprinting performance.

DESIGN

Cross-sectional.

METHODS

The relationships between HHD (prone isometric, prone break and supine break knee flexor strength tests), isokinetic and NHE peak knee flexor strength measures were examined using Pearson product correlations on 38 female footballers. A linear regression analysis was also performed for each pair of dependent variables (10 and 30 metre sprint times) and independent predictor variables (average relative peak torque for HHD, isokinetic and NHE testing).

RESULTS

There were good correlations between HHD tests (r = 0.81-0.90, p < 0.001, R2 = 0.65-0.82), moderate correlations between HHD and isokinetic peak torque, (r = 0.61-0.67, p < 0.001, R2 = 0.37-0.44) and poor association between the HHD peak torques and isokinetic work (r = 0.44-0.46, p = 0.005-0.007, R2 = 0.20-0.21) and average power (r = 0.39-0.45, n = 36, p = 0.006-0.019, R2 = 0.15-0.22). There was a poor association between NHE peak torque and isokinetic total work (r = 0.34, p = 0.04, R2 = 0.12). No associations between knee flexor strength and sprint times were observed (p = 0.12-0.79, r2 = 0.002-0.086).

CONCLUSIONS

Moderate to good correlations within HHD testing and poor to moderate correlations between HHD and isokinetic testing were observed. HHD knee flexor torque assessment may be useful to regularly chart the progress of hamstring rehabilitation for female footballers. Knee flexor strength assessments were not associated with sprint times in female footballers. Other aspects of knee flexor strength and sprint performance should be investigated to assist clinicians in making return to running and sprinting decisions in this population.

The Effect of Eccentric or Isometric Training on Strength, Architecture, and Sprinting across an Australian Football Season

PURPOSE

This study aimed to investigate the effect of an isometric (ISO) or Nordic hamstring exercise (NHE) intervention, alongside a sprint training program on hamstring strength, architecture, and sprinting performance in Australian footballers.

METHODS

Twenty-five male athletes undertook NHE ( n = 13) or ISO ( n = 12) training across a 38-wk period (including preseason and in season). Biceps femoris long head (BFlh) architecture, ISO, and eccentric knee flexor strength were assessed at baseline, at the end of preseason (14 wk), and at the conclusion of the intervention. Sprint times and force-velocity profiles were determined at baseline and at the end of preseason.

RESULTS

After the intervention, both groups had significant improvements in BFlh fascicle length (NHE: 1.16 cm, 95% CI = 0.68 to 1.63 cm, d = 1.88, P < 0.001; ISO: 0.82 cm, 95% CI = 0.57 to 1.06 cm, d = 1.70, P < 0.001), muscle thickness (NHE: 0.11 cm, 95% CI = 0.01 to 0.21 cm, d = 0.51, P = 0.032; ISO: 0.21 cm, 95% CI = 0.10 to 0.32 cm, d = 0.86, P = 0.002), and eccentric strength (NHE: 83 N, 95% CI = 53 to 114 N, d = 1.79, P < 0.001; ISO: 83 N, 95% CI = 17 to 151 N, d = 1.17, P = 0.018). Both groups also finished the intervention weaker isometrically than they started (NHE: -45 N, 95% CI = -81 to -8 N, d = -1.03, P = 0.022; ISO: -80 N, 95% CI = -104 to -56 N, d = -3.35, P < 0.001). At the end of preseason, the NHE group had improved their 5-m sprint time by 3.3% ± 2.0%), and their maximum horizontal velocity was 3% ± 2.1% greater than the ISO group who saw no changes.

CONCLUSIONS

Both ISO and NHE training with a periodized sprinting program can increase BFlh fascicle length, thickness, and eccentric strength in Australian footballers. NHE training also improves 5-m sprint time and maximum velocity. However, both interventions reduced ISO strength. These findings provide unique, contextually relevant insights into the adaptations possible in semiprofessional athletes.

Implementing hamstring injury prevention programmes remotely: a randomised proof of concept trial

Objectives

This study aimed to (1) compare the effectiveness of a Nordic hamstring exercise (NHE) versus single-leg Romanian deadlift (SLRDL) exercise programme on a hamstring injury risk surrogate; (2) compare the muscle soreness experienced by both exercise programmes; and (3) assess compliance to remote injury prevention exercise protocols through video software.

Methods

Twenty participants (10 women and 10 men: 21.45±1.6 years; 176±23 cm; 70±10 kg) were randomised into an NHE or SLRDL programme for 6 weeks. Single-leg hamstring bridge (SLHB), a hamstring injury surrogate, was the primary outcome for exercise efficacy. Muscle soreness and exercise adherence were also assessed. Significance was set at p<0.05.

Results

Both exercises increased SLHB performance resulting in an overall effect (p=0.013) with no effect for group (p=0.470) and no interaction effect (p=0.709), indicating both groups improved but there was no difference in improvement between interventions. There was no difference in muscle soreness between groups (p=0.087). Finally, both groups had 100% adherence to the programme.

Conclusions

Both the NHE and SLRDL are equally effective in increasing SLHB performance and demonstrate a similar level of muscle soreness. This suggests that SLRDL may be a viable option as a preventative exercise to mitigate the risk of hamstring injury. Finally, implementing injury prevention programmes remotely has the potential to enhance adherence.

Performing Nordic hamstring strength testing with additional weight affects the maximal eccentric force measured: do not compare apples to oranges

Background

Nordic hamstring test devices are commonly used to measure maximal eccentric hamstring force. The ability to control the final phase of the exercise has been adopted as a criterion to add weight when testing, without substantial evidence. We investigated if adding weight affected the maximal force measured, and if there were differences between players who could and could not control the final phase.

Methods

Female (n=84) and male (n=56) football players performed a Nordic hamstring strength test with 0, 5 and 10 kg. We used visual inspection to assess the ability to control the final phase (approximately last 20°), as per previously published studies.

Results

Maximal force was higher when tested with 5 kg (females: +8 N (2%), p<0.001; males: +18 N (4%), p<0.001) and 10 kg (females: +17 N (5%), p<0.001; males: +27 N (6%), p<0.001) compared with 0 kg. This was the case for both groups, those who could control the final phase (5 kg: +16 N (4%), p<0.001; 10 kg: +28 N (7%), p<0.001) and those who could not (5 kg: +9 N (3%), p<0.001; 10 kg: +15 N (4%), p<0.001).

Conclusion

Both players who could and could not control the final phase of the Nordic hamstring test demonstrated higher maximal force when adding weight to testing. Therefore, this should not be used to decide if players should perform testing with or without weight. Either all participants or none should be tested with weight, and the same approach should be used both for pre-testing and post-testing.

Nordic hamstring exercises in functional knee rehabilitation after anterior cruciate ligament reconstruction: a prospective, randomised, controlled study

To study the effect of using Nordic hamstring exercise method on muscle strength and knee joint stability of patients after ACL reconstruction. 60 patients admitted to our hospital for ACL reconstruction were randomly divided into a test group (n = 30, applying Nordic hamstring exercise) and a control group (n = 30, applying conventional rehabilitation training methods), and the difference in the circumference of the thighs of the patients in the two groups was analysed after training, and the peak torque (PT), total torque (PT), and flexion and extension strength were measured by using the Biodex system3 Multi-joint Isokinetic Testing System at knee joints with an angular velocity of 60°/s and 120°/s. The peak torque (PT), total work (TW), and average peak torque (AVG PT) were measured by extension and flexion strength at angular velocity, and the Lysholm Knee Score was used to assess the knee function of 60 patients. There was no difference in the difference in thigh circumference between the two groups before surgery (P > 0.05); the difference in thigh circumference between the patients in the test group at 12 and 24 weeks after surgery was (- 0.35 ± 0.22) cm and (0.12 ± 0.03) cm, respectively, which were higher than those in the control group, (- 0.51 ± 0.15) cm and (- 0.41 ± 0.34) cm (P < 0.05). At the 12th and 24th postoperative weeks, the popliteal muscle strength of both groups was improved compared with that before surgery; among them, by comparing the popliteal peak moments with different angular velocities, the ratio of popliteal peak moment on the affected side/peak moment on the healthy side of the popliteal muscle of the experimental group was significantly higher than that of the control group, and the difference was significant (P < 0.05), but there was still a gap compared with that of the healthy side. The Lachmen test and the anterior drawer test were negative in the test and control groups at the 24th postoperative week of review, and the anterior tibial shift was < 5 mm in the KT-1000 test, and the difference in the anterior shift was < 3 mm compared with the healthy side, and there was no significant difference between the two groups. By Nordic hamstring exercise can make patients after knee ACL reconstruction reduce patient pain, accelerate the recovery of knee function, improve the swelling of the lower limb, reach the level of flexor strength of the healthy side within 24 weeks, and can increase the stability of the knee joint.

The effects of hip- vs. knee-dominant hamstring exercise on biceps femoris morphology, strength, and sprint performance: a randomized intervention trial protocol

BACKGROUND

The hamstrings are an important muscle group that contribute to horizontal force during sprint acceleration and are also the most injured muscle group in running-based sports. Given the significant time loss associated with hamstrings injury and impaired sprinting performance following return to sport, identifying exercises that drive adaptations that are both protective of strain injury and beneficial to sprint performance is important for the strength and conditioning professional. This paper describes the study protocol investigating the effects of a 6-week training program using either the hip-dominant Romanian deadlift (RDL) or the knee-dominant Nordic hamstring exercise (NHE) on hamstring strain injury risk factors and sprint performance.

METHODS

A permuted block randomized (1:1 allocation) intervention trial will be conducted involving young, physically-active men and women. A target sample size of 32 will be recruited and enrolled participants will undergo baseline testing involving extended-field-of-view ultrasound imaging and shear wave elastography of the biceps femoris long head muscle, maximal hamstrings strength testing in both the RDL and NHE, and on-field sprint performance and biomechanics. Participants will complete the 6-week training intervention using either the RDL or NHE, according to group allocation. Baseline testing will be repeated at the end of the 6-week intervention followed by 2 weeks of detraining and a final testing session. The primary outcome will be regional changes in fascicle length with secondary outcomes including pennation angle, muscle cross sectional area, hamstring strength, and maximal sprint performance and biomechanics. An exploratory aim will determine changes in shear wave velocity.

DISCUSSION

Despite extensive research showing the benefits of the NHE on reducing hamstring strain injury risk, alternative exercises, such as the RDL, may offer similar or potentially even greater benefits. The findings of this study will aim to inform future researchers and practitioners investigating alternatives to the NHE, such as the RDL, in terms of their effectiveness in reducing rates of hamstring strain injury in larger scale prospective intervention studies.

TRIAL REGISTRATION

The trial is prospectively registered on ClinicalTrials.gov (NCT05455346; July 15, 2022).

The dose-response of pain throughout a Nordic hamstring exercise intervention

The Nordic hamstring exercise (NHE) reduces hamstring injury incidence. Compliance to large exercise volumes of the NHE is poor, with exercise related soreness often seen as a contributing factor. We investigated the dose-response of NHE exposure with delayed onset muscle soreness (DOMS) and non-DOMS pain. Forty males were randomized to a 6-week intervention of four different NHE dosages: Group 1: very low volume; Group 2: low volume; Group 3: initial high to low volume; Group 4: low to high volume. Group 4 experienced more DOMS (p < 0.05) and non-DOMS pain (p = 0.030) than other groups. High volumes of NHE increase DOMS and non-DOMS pain while lower volume protocols have lesser DOMS and non-DOMS pain responses.

Differences in Peak Knee Flexor Force between Eccentric-Only and Combined Eccentric-Concentric Nordic Hamstring Exercise

In many sports, the hamstring strain injury is a common injury. There is evidence that the Nordic hamstring exercise (NHE), a knee flexor exercise, can reduce hamstring injury risk in athletes. In research on hamstring injury prevention, eccentric-only NHE is typically performed, whereas in sports, it is relatively common for athletes to perform NHE eccentrically-concentrically. Further, NHE strength is generally assessed by measuring knee flexor force through an ankle brace, attached atop of a load cell. An alternative method might be to assess knee flexor force about the knee joint using a force plate. The aim of the study was to investigate differences in peak knee flexor force between eccentric-only and combined eccentric-concentric NHE. The purpose was also to determine the correlation between hamstring force measured at the ankle using a load cell (current gold standard) and force assessed about the knee joint using a force plate during NHE. Fifteen junior and senior elite soccer and track and field athletes (3 women and 12 men aged 17-27 years) performed eccentric NHE (ENHE) in which they leaned forward as far as possible until breakpoint and eccentric-concentric NHE (ECNHE) where they returned to the starting position. A linear encoder measured the position at which peak force occurred during the NHEs. Force assessed at the ankle differed significantly (678 vs. 600 N, p < 0.05), whereas force about the knee joint did not (640 vs. 607 N, p > 0.05) between ENHE and ECNHE (12 and 5% difference, respectively). The forward distance achieved by the participants in cm at breakpoint for ENHE was 37% higher than at the coupling phase for ECNHE (74 vs. 54 cm, p < 0.001). Very strong significant (p < 0.01) correlations were noted between peak force assessed at the ankle and about the knee joint for ENHE and ECNHE, r = 0.96 and r = 0.99, respectively. Our results suggest that ECNHE, where peak knee flexor force was reached with 37% less forward movement, may complement ENHE, i.e., during hamstring injury rehabilitation, where a position of great knee extension may not be well tolerated by the athlete. Further, assessing knee flexor force about the knee joint using a force plate may provide an alternative to measuring force at the ankle using a load cell when testing NHE strength.