Abstract
Background:
Neuromuscular training (NMT) has demonstrated efficacy as an intervention to decrease the risk of anterior cruciate ligament injuries and improve sports performance. The effect of this training on the mechanisms that contribute to improved physical performance has not been well defined.
Hypothesis:
Athletes in the NMT group will have better mechanisms of fundamental movements and agility tests that may contribute to improved sports performance.
Study Design:
Prospective cohort study
Level of Evidence:
Level 2
Methods:
Eight high school teams (111 athletes, 53% male, mean age 16 years) participated, with half performing NMT. Physical performance was measured using the dorsaVi ViPerform system, a US Food and Drug Administration-cleared wireless sensor system. Agility was assessed using a timed 3-cone test. Independent sample t tests were used to compare differences between the intervention and control groups.
Results:
Matched pre- and postseason data were collected from 74 athletes after excluding athletes with injury and those lost to follow-up. Significant improvements were observed in the NMT group for loading/landing speed ratios during a single-leg hop test (right lower extremity = −0.19 [–0.37, 0.03], P = 0.03 and left lower extremity = −0.27 [–0.50, −0.03], P = 0.03). The control group had lower ground reaction forces compared with the NMT group (P < 0.02), while significant improvements were found in the NMT group for initial peak acceleration (P < 0.02) and cadence (P = 0.01) during a straight-line acceleration/deceleration test. For the 3-cone agility test, the postseason time decreased compared with preseason in the NMT group, whereas the time for the control group increased (–0.37 s vs 0.14 s, P < 0.00).
Conclusion:
The results demonstrate that NMT administered by sports medicine clinicians can significantly improve some physical performance of fundamental movements in high school athletes.
Clinical Relevance:
Coaches should be trained to effectively deliver NMT in order to improve sports performance.
Keywords: ACL, biomechanics, injury prevention, neuromuscular training
Functional movements are the foundation for sports-related performance and motor skills. 5 Movement competency is also the basis for general physical development and motor learning.16,17 Weaknesses in individual movement strategies may predispose athletes to injury.3,4 Most anterior cruciate ligament (ACL) injuries in high-risk sports are noncontact injuries related to poor movement quality, such as the inability to decelerate over a planted leg with proper technique. Other biomechanical risk factors include high knee abduction movement and excessive valgus force on landing from a jump in which the knee is turned inwards in a “knock-kneed position.”24,25 These mechanics may result from lateral displacement of the trunk, unequal limb loading, or lack of neuromuscular control. 12 Most importantly, by improving these hazardous mechanics the risk of noncontact ACL injuries can be reduced. 12
The hallmark of ACL injury prevention is neuromuscular training (NMT), which incorporates exercises for balance, agility, and strengthening. NMT programs have been designed to be performed by athletes as part of the warm-up before practices and games. A meta-analysis of overlapping studies reported that NMT resulted in a 50% risk reduction in ACL injuries in both male and female athletes and an even higher reduction (67%) in noncontact ACL injuries in female athletes alone. 38 Other studies have shown that performing NMT 2 to 3 times per week for 10 to 15 min can lead to a reduction in ACL injuries.1,21,36
The ideal strategy to avoid these injuries altogether is to implement NMT that addresses modifiable risk factors to decrease the probability of noncontact ACL injuries. NMT has been developed for a variety of sports. One of the first, the Prevent Injury and Enhance Performance program, was designed to reduce ACL injuries in cutting or pivoting sports such as basketball, volleyball, and soccer. 19 The most well known is the Fédération Internationale de Football Association (FIFA) 11+ program for youth soccer players. 18 Most of these programs target adolescents, as opposed to younger children, due to physical maturity, body structure, and age-related injury mechanisms.6, 9 In one study, high school participants had greater improvements in their landing mechanics than pre-high school participants. 6
Although extensive efforts have been made to demonstrate the efficacy of NMT, low adherence to program recommendations by sports coaches limit their impact.13,37 Improved athletic performance related to NMT could improve adherence to the programs because coaches would have an additional incentive to train the athletes. In the systematic review of the impact of NMT on performance tests, we found that there was a variety of on-field tests to measure balance, sprinting, agility, jumping, physical fitness, and sport-specific tasks and that inclusion of plyometric and strengthening exercises were associated with beneficial effects. 15 However, the effect of this training on the mechanisms that contribute to improved physical performance has not been well defined. To better understand the factors that influence movement quality, measured by landing technique and body alignment on a series of tasks, the aim was to use wearable technology to compare lower extremity movements in high school athletes. We evaluated two groups of athletes, with one group performing NMT as their warm-up and the other group performing their usual warm-up. Our hypothesis was that the NMT group would show a greater improvement in movement quality (fundamental movements and agility), as measured by the wearable sensor device, that may contribute to improved sports performance.
Methods
Study Enrollment
Eight high school basketball and soccer teams were recruited for the study. Consent and assent forms were obtained from all participating parents and minors, respectively. This study was approved by the institutional review board (No. 2016–0811). The ethical principles for medical research involving human subjects as outlined in the Declaration of Helsinki were followed.
In half of the participating teams, experienced sports medicine clinicians from our institution delivered NMT as part of prepractice and pregame warm-ups over the course of a 12-week season. Each NMT session combined the key elements of multiple, validated programs including the FIFA 11+ and Prevent Injury and Enhance Performance programs,18,19 and included exercises that were organized into 5 phases: movement preparation, core stability, lower extremity strengthening, plyometrics, and agility (Appendix 1). The “A” and “B” versions of the programs were used on alternating days with the intermediate programs used during weeks 1 to 4, the advanced programs used during weeks 5 to 8, and the elite programs used during weeks 9 to 12 (Appendix 2). The NMT sessions were developed to be incorporated into training at the beginning of practices and competitions for 10 to 15 min. In addition to exercise instructions, athletes were provided with verbal and visual feedback regarding improper technique and corrective cues to improve movement quality. Teams in the control group performed their customary warm-up routine without the assistance of the clinicians. Teams were not randomly assigned to usual warm-up or NMT due to the logistics of the sports medicine clinicians being unable to travel to some of the teams, which were therefore assigned to the usual-warm up group. Coaches in both groups had no influence in this study other than leading the usual or NMT warm-up.
A total of 8 high school teams (4 basketball and 4 soccer) with 111 athletes (mean age 15, SD = 1) were recruited. Each group consisted of 4 teams in male and female soccer and basketball, although there was a different number of individual male and female athletes in both groups. Participant characteristics are listed in Table 1. A total of 8 athletes reported a current musculoskeletal injury and 11 athletes were cut from the team after preseason testing was performed. These 19 individuals were excluded from further analysis. In addition, 18 athletes were absent for postseason testing and were lost to follow-up. Thus, pre- and postseason data were collected from 74 athletes of a possible 92 athletes (80% follow-up).
Table 1.
Characteristics of participants recruited into the study
| Control (N = 40) | NMT (N = 71) | ||
|---|---|---|---|
| Demographics | Mean (SD) | Mean (SD) | P value |
| Age, years | 15.4 (1.3) | 15.8 (1.2) | 0.42 |
| Height, inches | 67.1 (5.3) | 67.5 (4.5) | 0.67 |
| Weight, pounds | 151.3 (43.1) | 146.4 (32.9) | 0.50 |
| Body mass index | 23.4 (4.5) | 21.9 (2.8) | 0.03 |
| N (%) | N (%) | ||
| Sex | |||
| Male | 19 (47.5) | 40 (56.3) | 0.37 |
| Female | 21 (52.5) | 31 (43.7) | |
| Lower extremity limb dominance (%) | |||
| Left | 4 (10.0) | 12 (16.9) | 0.32 |
| Right | 36 (90.0) | 59 (83.1) | |
| Previous ACL injury (%) | 1 (2.5) | 1 (1.4) | >0.99 |
ACL, anterior cruciate ligament.
Data Collection
Physiological measurements were obtained using dorsaVi wearable sensor technology (dorsaVi Ltd). The dorsaVi system utilizes wireless inertial measurement unit sensors that include a magnetometer (to measure position), accelerometer (to measure force), and gyroscope (to measure rotation). The sensors are mounted on the midshaft of each tibia and are specifically designed to collect objective data that can be used in standardized testing protocols. Sensor placement is standardized with templates utilizing a stable bony landmark on the tibia with fast angulation movements. Briefly, the back of the ruler was placed at the inferior border of the medial malleolus on the left leg. Then, a horizontal line was marked with a pen on the tibia of the appropriate height demarcation found on the ruler. A vertical line was also marked at the same level on both the medial and lateral borders of the tibia to ensure that the center placement was on the bony tibia itself. This process was repeated for the right leg. Following prompts from the software, sensors were placed on the tibia, making sure that the line marked on the tibia bisected the pegs of the disposable application pads. The sensors were placed vertically on the tibia, not on the surrounding soft tissue. Both the left and right sensors were placed at equal heights on the tibia. The sampling frequency was 200 sample points per second. For knee assessments, the sampling was done at 50 Hz. For running assessments, the sampling was done at 100 Hz.
All tests were administered indoors immediately prior to and following each sports season (12 weeks apart). Kinematics were assessed during the performance of 5 repetitions of the following activities: double-leg and single-leg squats, single-leg hop (bilaterally), and straight-line running acceleration and deceleration. Agility was assessed using a standard 3-cone agility test. Participants were required to wear athletic shoes (sneakers) and were provided with 1 to 2 min of rest between each activity.
For the squat tests, measures of squat speed and tibial inclination were recorded. For the single-leg hop test, measures of hop speed ratio, hop flight time (time from maximum tibial inclination during hop loading to landing), and tibial inclination were recorded. In addition, athletes performed a straight-line run test to assess acceleration and deceleration. The dorsaVi system evaluates limb symmetry during running activities by measuring ground-reaction forces (GRFs), ground contact time, initial peak acceleration, and cadence. It has been shown to have excellent reliability (intraclass correlation = 0.88) in calculating an athlete’s lower extremity load when running in a straight line at constant velocity. 32 A description of each measurement can be found in Table 2, as well as whether a positive or negative value is considered an improvement.
Table 2.
Description of each measure evaluated by the dorsaVi system
| Measure | Description | Coefficient of variation (SD/mean) |
|---|---|---|
| Single- and Double-Leg Squat | ||
| Squat speed | The speed at which the tibia translates anteriorly during the single- and double-leg squat exercises. Negative value is an improvement | Single left = 0.30 Right = 0.31 Double left = 0.34 Right = 0.38 |
| Anterior tibial translation | The number of degrees that the tibia translates anteriorly during the single- and double-leg squat exercises. Negative value is an improvement | Single left = 0.17 Right = 0.21 Double left = 0.24 Right = 0.25 |
| Medial/lateral tibial translation | The number of degrees that the tibia translates medially or laterally during the single- and double-leg squat exercises. Positive value is an improvement. | Single left = 0.17 Right = 0.27 Double left = 0.24 Right = 0.31 |
| Single-Leg Hop | ||
| Hop speed ratio | The speed at which the tibia translates anteriorly during the loading phase of the hop/the speed at which the tibia translates anteriorly during the landing phase of the hop. Negative value is an improvement | Left = 0.65 Right = 0.68 |
| Hop flight time | The amount of time from take-off to landing. Positive value is an improvement | Left = 0.39 Right = 0.43 |
| Medial/lateral tibial translation | The number of degrees that the tibia translates medially or laterally during the single-leg hop. Positive value is an improvement | Left = 0.20 Right = 0.22 |
| Acceleration/Deceleration | ||
| Ground reaction force | The amount of force measured in each limb in newtons. Negative value is an improvement | Left = 0.13 Right = 0.14 |
| Initial peak acceleration | A measure of acceleration in gravitational force equivalent (g). Positive value is an improvement | Left = 0.18 Right = 0.19 |
| Ground contact time | The amount of time that each limb is in contact with the ground, measured in milliseconds. Negative value is an improvement | Left = 0.16 Right = 0.17 |
| Cadence | The total number of steps/minutes measured during this activity. Positive value is an improvement | 0.10 |
| 3-Cone Agility Test | ||
| Time | The total amount of time to complete the activity (in seconds). Negative value is an improvement | 0.12 |
GRF measures the average vertical force applied to the ground during the mid-stance phase of the gait cycle and is measured in newtons (N). Vertical GRF values increase as running speed increases. Research has shown that high values of peak vertical GRF are associated with increased vertical displacement, which has been shown to reduce running economy.10,29,35 GRF is derived from body weight, a dorsaVi algorithm, and initial peak acceleration, which measures the vertical acceleration and loading rate through the tibia when the foot strikes the ground at initial contact and is measured in g (acceleration due to gravity).
Statistical Analysis
Means and standard deviations were reported for continuous variables. Frequencies and percentages were reported for categorical variables. Differences within groups were compared post- minus preseason testing using a paired t test. The primary outcome of this study was the differences between the NMT and control groups. All outcomes were assessed using a factorial (2-way) analysis of variance test to assess the difference in the improvement between the two groups (NMT minus control). The two factors were NMT or control group and dominant or nondominant side with an interaction term. When significant interaction was present, pairwise comparisons were performed with Tukey adjustment for multiple comparisons. All analyses were performed using R. Statistical significance was set at P < 0.05.
In a post hoc power analysis, with a sample size of 74 participants, difference of 0.51, and standard deviation of 0.13 on the 3-cone test, the author(s) achieved power of >0.99 using the 2 independent samples t test.
Results
The characteristics of study participants are listed in Table 1. When comparing within-group differences (postseason-preseason) following training, the NMT group showed greater improvements on the double-leg squat for squat speed left (P < 0.00), squat speed right (P = 0.001), anterior tibial translation left (P = 0.02), and medial/lateral tibial translation right (P = 0.03). On the single-leg hop, only the control group showed worse performance on hop speed (P = 0.01) and flight time (left P = 0.05 and right P = 0.00). On the straight-leg run, the control group had lower GRF (left P = 0.01 and right P = 0.05). They had worse acceleration post season (right P < 0.00). Only the NMT group improved to a faster time (P < 0.00) (Table 3).
Table 3.
Results of pre- and postseason testing in 74 athletes included in the analysis
| Intervention | Control | ||||||
|---|---|---|---|---|---|---|---|
| Exercise | Measure | Difference (Post, Pre) |
95% CI | P value | Difference (Post, Pre) |
95% CI | P value |
| Single-Leg Squat | |||||||
| Squat speed average left | −4.38 (22.47, 26.85) |
(−6.41, −2.35) | <0.00 | −1.88 (26.11, 27.99) |
(−5.35, 1.59) | 0.28 | |
| Squat speed average right | −3.55 (26.50, 30.05) |
(−6.48, −0.62) | 0.02 | −5.23 (24.58, 29.81) |
(−8.59, −1.88) | 0.00 | |
| Anterior tibial translation average left | −0.06 (37.00, 37.06) |
(−1.62, 1.50) | 0.94 | 1.49 (39.59, 38.10) |
(−0.71, 3.68) | 0.18 | |
| Anterior tibial translation average right | 1.37 (37.33, 35.96) |
(−0.48, 3.22) | 0.14 | 1.25 (37.12, 35.87) |
(−1.88, 4.39) | 0.42 | |
| Medial lateral tibial translation average left | 0.22 (3.80, 3.58) |
(0.05, 0.40) | 0.01 | 0.05 (3.53, 3.48) |
(−0.16, 0.25) | 0.64 | |
| Medial lateral tibial translation average right | 0.1 (3.17, 3.07) |
(−0.13, 0.33) | 0.38 | 0.3 (3.28, 2.98) |
(0.04, 0.55) | 0.02 | |
| Double-Leg Squat | |||||||
| Squat speed translation average left | −3.38 (19.11, 22.50) |
(−4.93, −1.84) | <0.00 | −3.77 (22.50, 26.27) |
(−6.45, −1.08) | 0.01 | |
| Squat speed translation average right | −4.34 (19.92, 24.26) |
(−7.01, −1.85) | 0.00 | −0.39 (22.97, 23.36) |
(−3.32, 2.53) | 0.78 | |
| Anterior tibial translation average left | −2.23 (33.00, 35.23) |
(−4.02, −0.45) | 0.02 | −0.79 (39.45, 40.24) |
(−2.96, 1.38) | 0.46 | |
| Anterior tibial translation average right | −2.33 (31.89, 34.22) |
(−4.74, 0.09) | 0.06 | −2.45 (36.59, 39.04) |
(−4.84, −0.06) | 0.05 | |
| Medial/lateral tibial translation average left | 0.11 (4.11, 4.00) |
(−0.17, 0.39) | 0.44 | 0.03 (3.59, 3.56) |
(−0.32, 0.38) | 0.86 | |
| Medial/lateral tibial translation average right | 0.32 (3.82, 3.50) |
(0.03, 0.61) | 0.03 | 0.03 (3.32, 3.29) |
(−0.39, 0.45) | 0.90 | |
| Single-Leg Hop | |||||||
| Hop speed ratio average left | −0.13 (0.67, 0.80) |
(−0.31, 0.04) | 0.13 | 0.12 (0.74, 0.62) |
(0.03, 0.21) | 0.01 | |
| Hop speed ratio average right | −0.10 (0.63, 0.73) |
(−0.21, 0.01) | 0.08 | 0.11 (0.70, 0.59) |
(−0.01, 0.22) | 0.08 | |
| Hop flight time average left | −0.01 (0.19, 0.20) |
(−0.04, 0.02) | 0.43 | −0.03 (0.19, 0.22) |
(−0.06, 0.00) | 0.05 | |
| Hop flight time average right | −0.02 (0.19, 0.21) |
(−0.05, 0.02) | 0.30 | −0.06 (0.17, 0.23) |
(−0.10, −0.02) | 0.00 | |
| Medial/lateral tibial translation average left | 0.21 (3.44, 3.23) |
(0.02, 0.39) | 0.26 | −0.01 (3.61, 3.62) |
(−0.23, 0.24) | 0.97 | |
| Medial/lateral tibial translation average right | 0.09 (3.41, 3.32) |
(−0.25, 0.43) | 0.61 | 0.05 (3.60, 3.55) |
(−0.32, 0.42) | 0.80 | |
| Straight-Leg Run | |||||||
| Ground force reaction left | 37.93 (2445.16, 2407.22) |
(−15.71, 91.58) | 0.16 | −98.41 (2348.90, 2447.31) |
(−171.80, −25.03) | 0.01 | |
| Ground force reaction right | 17.93 (2451.91, 2433.98) |
(−26.18, 62.04) | 0.42 | −92.07 (2342.10, 2434.17) |
(−184.61, 0.47) | 0.06 | |
| Initial peak acceleration left | −0.07 (9.28, 9.35) |
(−0.60, 0.47) | 0.80 | −1.10 (7.90, 9.00) |
(−1.79, −0.42) | 0.00 | |
| Initial peak acceleration right | −0.44 (9.00, 9.44) |
(−1.05, 0.17) | 0.15 | −1.38 (7.82, 9.20) |
(−1.91, −0.85) | <0.00 | |
| Ground contact time left | −2.56 (156.13, 158.69) |
(−9.26, 4.15) | 0.45 | 7.07 (158.86, 151.79) |
(−0.51, 14.65) | 0.07 | |
| Ground contact time right | 0.31 (160.22, 159.91) |
(−6.37, 6.99) | 0.93 | 7.59 (161.72, 154.13) |
(−0.56, 15.73) | 0.07 | |
| Cadence | 4.71 (231.95, 227.24) |
(−2.53, 11.95) | 0.20 | −7.41 (221.48, 228.89) |
(−13.73, −1.04) | 0.02 | |
| 3-Cone Test | Time | −0.37 (9.09, 9.46) |
(−0.19, −0.55) | <0.00 | 0.14 (10.19, 10.05) |
(−0.07, 0.34) | 0.18 |
CI, confidence interval.
When comparing between groups, there were no significant differences for either the single- or double-leg squat between the NMT and control groups. Hop speed on the single-leg hop test was different for both the right (−0.19 [−0.37, −0.03], P = 0.03) and left lower extremity (−0.27 [−0.50, −0.03], P = 0.03) in favor of an improvement for the NMT group. There were also significant improvements on the straight-line running test in favor of the NMT group for initial peak acceleration: right (1.05 [0.19, 1.92], P = 0.02) and left lower extremity (1.15 [0.29, 2.01], P = 0.01) and cadence (12.12 [2.65, 21.60], P = 0.01). GRFs favored the control group, which had lower values compared with the NMT group: right (111.83 [19.99, 203.66], P = 0.02) and left lower extremity (141.43 [56.92, 225.94], P = 0.00). For the 3-cone agility test, the postseason completion time was lower than the preseason time in the NMT group, whereas the time for the control group increased postseason (−0.51 [−0.78, −0.24], P < 0.00). Comparisons for the NMT versus control group can be found in Table 4.
Table 4.
Results of the factorial analysis of variance comparing the intervention versus control group and dominant versus nondominant side.
| Intervention-Control | Dominant-Nondominant | Interaction | ||||||
|---|---|---|---|---|---|---|---|---|
| Exercise | Measure | Difference | 95% CI | P value | Difference | 95% CI | P value | P value |
| Single-Leg Squat | ||||||||
| Squat speed average left | −2.67 | −6.43, 1.08 | 0.16 | 1.89 | −3.02, 6.82 | 0.44 | 0.31 | |
| Squat speed average right | 1.15 | −3.37, 5.66 | 0.61 | −1.31 | −7.23, 4.61 | 0.66 | 0.81 | |
| Anterior tibial translation average left | −1.57 | −4.15, 1.00 | 0.23 | 1.26 | −2.12, 4.64 | 0.46 | 0.05 | |
| Anterior tibial translation average right | 0.12 | −3.22, 3.45 | 0.95 | 3.73 | −0.65, 8.11 | 0.09 | 0.16 | |
| Medial/lateral tibial translation average left | 0.17 | −0.1, 0.44 | 0.22 | −0.08 | −0.44, 0.27 | 0.65 | 0.23 | |
| Medial/lateral tibial translation average Right | −0.22 | −0.55, 0.13 | 0.22 | −0.42 | −0.86, 0.03 | 0.07 | 0.27 | |
| Double-Leg Squat | ||||||||
| Squat speed average left | 0.53 | −2.27, 3.34 | 0.71 | −1.39 | −5.07, 2.28 | 0.45 | 0.04 | |
| Squat speed average right | −3.59 | −7.39, 0.21 | 0.06 | 4.71 | −0.26, 9.67 | 0.06 | 0.12 | |
| Anterior tibial translation average left | −1.19 | −3.82, 1.45 | 0.37 | −5.56 | −9.01, -2.10 | 0.00 | 0.99 | |
| Anterior tibial translation average right | 0.33 | −2.96, 3.62 | 0.84 | 7.67 | 3.36, 11.97 | <0.00 | 0.53 | |
| Medial/lateral tibial translation average left | 0.08 | −0.36, 0.52 | 0.71 | −0.17 | −0.75, 0.41 | 0.55 | 0.03 | |
| Medial/lateral tibial translation average right | 0.27 | −0.19, 0.74 | 0.25 | −0.71 | −1.32, −0.09 | 0.02 | 0.06 | |
| Single-Leg Hop | ||||||||
| Hop speed ratio average left | −0.27 | −0.5, −0.03 | 0.03 | 0.06 | −0.25, 0.36 | 0.71 | 0.13 | |
| Hop speed ratio average right | −0.19 | −0.37, −0.03 | 0.03 | 0.06 | −0.27, 0.28 | 0.62 | 0.20 | |
| Hop flight time average left | 0.02 | −0.02, 0.06 | 0.36 | 0.002 | −0.06, 0.06 | 0.93 | 0.34 | |
| Hop flight time average right | 0.04 | −0.01, 0.09 | 0.11 | −0.07 | −0.14, −0.01 | 0.03 | 0.19 | |
| Medial/lateral tibial translation average left | 0.21 | −0.08, 0.51 | 0.16 | −0.07 | −0.46, 0.32 | 0.72 | 0.81 | |
| Medial/lateral tibial translation average right | 0.002 | −0.51, 0.51 | 0.99 | −0.35 | −1.03, 0.32 | 0.30 | 0.28 | |
| Acceleration Deceleration | ||||||||
| Ground force reaction left | 141.43 | 56.92, 225.94 | 0.00 | −100.51 | −211.39, 10.36 | 0.08 | 0.02 | |
| Ground force reaction right | 111.83 | 19.99, 203.66 | 0.02 | −88.03 | −208.51, 32.45 | 0.15 | 0.91 | |
| Initial peak acceleration left | 1.15 | 0.29, 2.01 | 0.01 | 0.12 | −1, 1.25 | 0.83 | 0.90 | |
| Initial peak acceleration right | 1.05 | 0.19, 1.92 | 0.02 | 0.05 | −0.93, 1.18 | 0.93 | 0.80 | |
| Ground contact time left | −9.48 | −19.88, 0.92 | 0.07 | −1.97 | −15.61, 11.67 | 0.77 | 0.25 | |
| Ground contact time right | −7.43 | −18.15, 3.27 | 0.17 | −1.99 | −16.04, 12.06 | 0.78 | 0.55 | |
| Cadence | 12.12 | 2.65, 21.6 | 0.01 | - | - | - | - | |
| 3-Cone Test | ||||||||
| Time | −0.51 | −0.78, −0.24 | <0.00 | - | - | - | - | |
When evaluating the effects of the dominant or nondominant sides on the difference between the NMT or control groups, the interaction was significant for squat speed left (P = 0.04) and medial/lateral tibial translation left (P = 0.03) on the double-leg squat. No significant pairwise comparisons were found with the Tukey adjustment for multiple comparisons. The interaction term was also significant for GRF left (P = 0.02). In the pairwise comparisons, the improvement was in favor of the control right-dominant participants compared to the NMT right-dominant participants (191.56 [70.93, 312.19], P < 0.00). In addition, participants in the NMT group who were left-dominant had lower GRFs compared with those who were right-dominant (-185.33 [-358.01, -12.65], P = 0.03).
Discussion
While avoiding ACL injuries is an optimal risk management strategy, widespread implementation of NMT in youth sports remains challenging. 37 ACL injury rates continue to increase over time, particularly in the pediatric population. 7 Our findings show that NMT administered by well-trained sports medicine clinicians can improve movement quality and agility among high school athletes. The messaging for enhanced performance through the use of NMT may be one strategy for increasing the uptake of these programs.
For the straight-line running test, the control group had significantly lower peak GRFs, slower initial peak acceleration, and a slower running cadence compared with the NMT group. Considered collectively, the lower GRFs demonstrated by the control group following training may be a function of slower running speed. GRF measurements can be used to help interpret the ground contact phases of running. Hamill et al 11 reported that significant differences in GRFs were found at different running speeds, whereas Munro et al 22 reported that GRFs are running-speed dependent, with greater GRF observed at high running speeds. However, the higher GRF in the NMT group was still an unexpected finding. While this effect could be due to running speed, these results should be interpreted with caution, as there could be other possible explanations for this negative finding in the intervention group.
This study used the 3-cone test, which is used in the NFL Combine, to measure speed and agility. We found that the intervention group demonstrated lower test times compared with the control group. Other studies that investigated the T agility test in high school basketball and soccer players showed significant improvements when the NMT included agility exercises and were performed 2 to 3 times each week.6,20,27,30,31 Similar to these results, studies that use NMT that incorporates plyometric exercises have reported a significant benefit on the single-leg hop test.8,14,23,33 Thus, NMT can improve performance on these particular tests, although the clinical significance of these improvements is unclear.
In this study, no differences were found between the NMT and control groups on static single- and double-leg squats. It is possible that our findings were because half of the teams in the study played soccer. Sports such as basketball and volleyball likely require more jumping ability and leg power compared with a running sport such as soccer.26-28 Another study observed significant improvements on the squat in female athletes when using a NMT that included resistance training, which was not included in our NMT program. 23 Type of exercise performed or type of measurement used could also explain the lack of a difference for the single- and double-leg squats that was found in this study.
Advocating for coaches to implement NMT warm-ups for athletes as performance enhancement in addition to injury prevention may be an effective strategy for improving adherence. There are conflicting reports on whether NMT programs have a direct benefit on physical performance, 2 despite the fact that many studies were conducted in similar settings and populations. 34 A systematic review evaluated the effect of NMT on sports performance tests and determined that the largest number of studies evaluated jumping tests. 15 The findings varied greatly, in some cases even leading to a decrease in jumping ability. The review also found that inclusion of plyometric and strengthening exercises was generally associated with beneficial effects. We included a control group for comparison to measure the effect of NMT beyond the effect of sports-related physical activity. In the same systematic review, the majority of cohort studies (67%) were rated as poor quality based on the lack of a control group. 15
This study was limited by the inability to randomly assign teams to the NMT or control group due to the availability and geographic location of the sports medicine clinicians who were responsible for leading the NMT routines. We also did not record the warm-up exercises in the control group or any information on adherence. The follow-up rate was 80%, which was acceptable because the study involved extensive pre- and postseason testing. The control group had a higher proportion of female athletes, although the effect on the study findings is unclear. Although they are more likely to have biomechanical predisposition to injury, there is no evidence for sex differences on performance. Furthermore, GRF was reported in newtons, which makes it difficult to compare across participants of varying body weights, as larger individuals will exhibit larger GRFs in newtons.
The beneficial effects of NMT on sports performance can be used to change the messaging for NMT away from injury prevention only to also having performance enhancement as a benefit. This may be an effective strategy for large-scale implementation of NMT in high school sports.
Supplemental Material
Supplemental material, sj-pdf-1-sph-10.1177_19417381221089917 for A Controlled Trial of the Effects of Neuromuscular Training on Physical Performance in Male and Female High School Athletes by Daphne I. Ling, Joseph Janosky, Brandon Schneider, James Russomano, Caroline Boyle, James Kinderknecht and Robert G. Marx in Sports Health: A Multidisciplinary Approach
Supplemental material, sj-pdf-2-sph-10.1177_19417381221089917 for A Controlled Trial of the Effects of Neuromuscular Training on Physical Performance in Male and Female High School Athletes by Daphne I. Ling, Joseph Janosky, Brandon Schneider, James Russomano, Caroline Boyle, James Kinderknecht and Robert G. Marx in Sports Health: A Multidisciplinary Approach
Footnotes
The following authors declared potential conflicts of interest: R.G.M. received personal fees support from Journal of Bone and Joint Surgery, Journal of Bone and Joint Surgery Evidence Based Orthopedics, Springer and Demos Health, and Mend.
ORCID iD: Daphne I. Ling 
https://orcid.org/0000-0003-4415-2471
References
- 1.Alentorn-Geli E, Myer GD, Silvers HJ, et al. Prevention of non-contact anterior cruciate ligament injuries in soccer players. Part 2: a review of prevention programs aimed to modify risk factors and to reduce injury rates. Knee Surg Sports Traumatol Arthrosc. 2009;17:859-879. [DOI] [PubMed] [Google Scholar]
- 2.Ayala F, Pomares-Noguera C, Robles-Palazón FJ, et al. Training effects of the FIFA 11+ and Harmoknee on several neuromuscular parameters of physical performance measures. Int J Sports Med. 2017;38:278-289. [DOI] [PubMed] [Google Scholar]
- 3.Cook G, Burton L, Hoogenboom B. Pre-participation screening: the use of fundamental movements as an assessment of function - part 1. N Am J Sports Phys Ther. 2006;1:62-72. [PMC free article] [PubMed] [Google Scholar]
- 4.Cook G, Burton L, Hoogenboom B. Pre-participation screening: the use of fundamental movements as an assessment of function - part 2. N Am J Sports Phys Ther. 2006;1:132-139. [PMC free article] [PubMed] [Google Scholar]
- 5.Cook G, Burton L, Hoogenboom BJ, et al. Functional movement screening: the use of fundamental movements as an assessment of function - part 2. Int J Sports Phys Ther. 2014;9:549-563. [PMC free article] [PubMed] [Google Scholar]
- 6.DiStefano LJ, Padua DA, Blackburn JT, et al. Integrated injury prevention program improves balance and vertical jump height in children. J Strength Cond Res. 2010;24:332-342. [DOI] [PubMed] [Google Scholar]
- 7.Dodwell ER, Lamont LE, Green DW, et al. 20 Years of pediatric anterior cruciate ligament reconstruction in New York State. Am J Sports Med. 2014;42:675-680. [DOI] [PubMed] [Google Scholar]
- 8.Faigenbaum AD, Myer GD, Farrell A, et al. Integrative neuromuscular training and sex-specific fitness performance in 7-year-old children: an exploratory investigation. J Athl Train. 2014;49:145-153. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Grandstrand SL, Pfeiffer RP, Sabick MB, et al. The effects of a commercially available warm-up program on landing mechanics in female youth soccer players. J Strength Cond Res. 2006;20:331-335. [DOI] [PubMed] [Google Scholar]
- 10.Halvorsen K, Eriksson M, Gullstrand L. Acute effects of reducing vertical displacement and step frequency on running economy. J Strength Cond Res. 2012;26:2065-2070. [DOI] [PubMed] [Google Scholar]
- 11.Hamill J, Bates BT, Knutzen KM, et al. Variations in ground reaction force parameters at different running speeds. Human Movement Sci. 1983;2:47-56. [Google Scholar]
- 12.Hewett TE, Ford KR, Hoogenboom BJ, et al. Understanding and preventing ACL injuries: current biomechanical and epidemiologic considerations - update 2010. N Am J Sports Phys Ther. 2010;5:234-251. [PMC free article] [PubMed] [Google Scholar]
- 13.Joy EA, Taylor JR, Novak MA, et al. Factors influencing the implementation of anterior cruciate ligament injury prevention strategies by girls soccer coaches. J Strength Cond Res. 2013;27:2263-2269. [DOI] [PubMed] [Google Scholar]
- 14.Leporace G, Praxedes J, Pereira GR, et al. Influence of a preventive training program on lower limb kinematics and vertical jump height of male volleyball athletes. Phys Ther Sport. 2013;14:35-43. [DOI] [PubMed] [Google Scholar]
- 15.Ling DI, Cepeda NA, Marom N, Jivanelli B, Marx RG. Injury prevention programmes with plyometric and strengthening exercises improve on-field performance: a systematic review. J ISAKOS. 2020;5:48-59. [Google Scholar]
- 16.Lloyd RS, Oliver JL, Faigenbaum AD, et al. Long-term athletic development - part 1: a pathway for all youth. J Strength Cond Res. 2015;29:1439-1450. [DOI] [PubMed] [Google Scholar]
- 17.Lloyd RS, Oliver JL, Faigenbaum AD, et al. Long-term athletic development, part 2: barriers to success and potential solutions. J Strength Cond Res. 2015;29:1451-1464. [DOI] [PubMed] [Google Scholar]
- 18.Longo UG, Loppini M, Berton A, et al. The FIFA 11+ program is effective in preventing injuries in elite male basketball players: a cluster randomized controlled trial. Am J Sports Med. 2012;40:996-1005. [DOI] [PubMed] [Google Scholar]
- 19.Mandelbaum BR, Silvers HJ, Watanabe DS, et al. Effectiveness of a neuromuscular and proprioceptive training program in preventing anterior cruciate ligament injuries in female athletes: 2-year follow-up. Am J Sports Med. 2005;33:1003-1010. [DOI] [PubMed] [Google Scholar]
- 20.Miller MG, Herniman JJ, Ricard MD, et al. The effects of a 6-week plyometric training program on agility. J Sports Sci Med. 2006;5:459-465. [PMC free article] [PubMed] [Google Scholar]
- 21.Monajati A, Larumbe-Zabala E, Goss-Sampson M, et al. The effectiveness of injury prevention programs to modify risk factors for non-contact anterior cruciate ligament and hamstring injuries in uninjured team sports athletes: a systematic review. PLoS ONE. 2016;11:e0155272. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Munro CF, Miller DI, Fuglevand A. Ground reaction forces in running: a reexamination. J Biomech. 1987;20:147-155. [DOI] [PubMed] [Google Scholar]
- 23.Myer GD, Ford KR, Brent JL, et al. The effects of plyometric vs. dynamic stabilization and balance training on power, balance, and landing force in female athletes. J Strength Cond Res. 2006;20:345-353. [DOI] [PubMed] [Google Scholar]
- 24.Myer GD, Ford KR, Khoury J, et al. Clinical correlates to laboratory measures for use in non-contact anterior cruciate ligament injury risk prediction algorithm. Clin Biomech (Bristol, Avon). 2010;25:693-699. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.Nessler T, Denney L, Sampley J. ACL injury prevention: what does research tell us? Curr Rev Musculoskelet Med. 2017;10:281-288. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26.Noyes FR, Barber-Westin SD, Smith ST, et al. A training program to improve neuromuscular indices in female high school volleyball players. J Strength Cond Res. 2011;25:2151-2160. [DOI] [PubMed] [Google Scholar]
- 27.Noyes FR, Barber-Westin SD, Smith ST, et al. A training program to improve neuromuscular and performance indices in female high school basketball players. J Strength Cond Res. 2012;26:709-719. [DOI] [PubMed] [Google Scholar]
- 28.Noyes FR, Barber-Westin SD, Tutalo Smith ST, et al. A training program to improve neuromuscular and performance indices in female high school soccer players. J Strength Cond Res. 2013;27:340-351. [DOI] [PubMed] [Google Scholar]
- 29.Nummela A, Keränen T, Mikkelsson LO. Factors related to top running speed and economy. Int J Sports Med. 2007;28:655-661. [DOI] [PubMed] [Google Scholar]
- 30.OʼMalley E, Murphy JC, McCarthy Persson U, et al. The effects of the Gaelic Athletic Association 15 training program on neuromuscular outcomes in Gaelic football and hurling players: a randomized cluster trial. J Strength Cond Res. 2017;31:2119-2130. [DOI] [PubMed] [Google Scholar]
- 31.Pasanen K, Parkkari J, Pasanen M, et al. Effect of a neuromuscular warm-up programme on muscle power, balance, speed and agility: a randomised controlled study. Br J Sports Med. 2009;43:1073-1078. [DOI] [PubMed] [Google Scholar]
- 32.Raper DP, Witchalls J, Philips EJ, et al. Use of a tibial accelerometer to measure ground reaction force in running: a reliability and validity comparison with force plates. J Sci Med Sport. 2018;21:84-88. [DOI] [PubMed] [Google Scholar]
- 33.Reis I, Rebelo A, Krustrup P, et al. Performance enhancement effects of Fédération Internationale de Football Association’s “The 11+” injury prevention training program in youth futsal players. Clin J Sport Med. 2013;23:318-320. [DOI] [PubMed] [Google Scholar]
- 34.Steffen K, Bakka HM, Myklebust G, et al. Performance aspects of an injury prevention program: a ten-week intervention in adolescent female football players. Scand J Med Sci Sports. 2008;18:596-604. [DOI] [PubMed] [Google Scholar]
- 35.Støren Ø, Helgerud J, Hoff J. Running stride peak forces inversely determine running economy in elite runners. J Strength Cond Res. 2011;25:117-123. [DOI] [PubMed] [Google Scholar]
- 36.Sugimoto D, Myer GD, Barber Foss KD, et al. Critical components of neuromuscular training to reduce ACL injury risk in female athletes: meta-regression analysis. Br J Sports Med. 2016;50:1259-1266. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 37.Sugimoto D, Myer GD, Bush HM, et al. Compliance with neuromuscular training and anterior cruciate ligament injury risk reduction in female athletes: a meta-analysis. J Athl Train. 2012;47:714-723. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 38.Webster KE, Hewett TE. Meta-analysis of meta-analyses of anterior cruciate ligament injury reduction training programs. J Orthop Res. 2018;36:2696-2708. [DOI] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Supplemental material, sj-pdf-1-sph-10.1177_19417381221089917 for A Controlled Trial of the Effects of Neuromuscular Training on Physical Performance in Male and Female High School Athletes by Daphne I. Ling, Joseph Janosky, Brandon Schneider, James Russomano, Caroline Boyle, James Kinderknecht and Robert G. Marx in Sports Health: A Multidisciplinary Approach
Supplemental material, sj-pdf-2-sph-10.1177_19417381221089917 for A Controlled Trial of the Effects of Neuromuscular Training on Physical Performance in Male and Female High School Athletes by Daphne I. Ling, Joseph Janosky, Brandon Schneider, James Russomano, Caroline Boyle, James Kinderknecht and Robert G. Marx in Sports Health: A Multidisciplinary Approach