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. Author manuscript; available in PMC: 2019 May 1.
Published in final edited form as: J Orthop Res. 2017 Nov 28;36(5):1391–1397. doi: 10.1002/jor.23784

No Difference Between Mechanical Perturbation Training with Compliant Surface and Manual Perturbation Training on Knee Functional Performance After ACL Rupture†

Zakariya Nawasreh 1, David Logerstedt 3,4, Mathew Failla 2, Lynn Snyder-Mackler 2,4,5
PMCID: PMC5924420  NIHMSID: NIHMS921496  PMID: 29077216

Abstract

Manual perturbation training improves dynamic knee stability and functional performance after anterior cruciate ligament rupture (ACL-rupture). However, it is limited to static standing position and does not allow time-specific perturbations at different phase of functional activities. The purpose of this study was to investigate whether administering mechanical perturbation training including compliant surface provides effects similar to manual perturbation training on knee functional measures after an acute ACL-rupture.

Sixteen level I/II athletes with ACL-ruptures participated in this preliminary study. Eight patients received mechanical (Mechanical) and 8 subjects received manual perturbation training (Manual). All patients completed a functional testing (isometric quadriceps strength, single-legged hop tests) and patient-reported measures (Knee Outcome Survey- Activities of Daily Living Scale (KOS-ADLS), Global Rating Score (GRS), International Knee Documentation Committee 2000 (IKDC 2000) at pre- and post-training. 2×2 ANOVA was used for data analysis. No significant group-by-time interactions were found for all measures (p>0.18). Main effects of time were found for single hop (Pre-testing: 85.14%+21.07; Post-testing: 92.49%+17.55), triple hop (Pre-testing: 84.64%+14.17; Post-testing: 96.64%+11.14), KOS-ADLS (Pre-testing: 81.13%+11.12; Post-testing: 88.63%+12.63), GRS (Pre-testing: 68.63%+15.73; Post-testing: 78.81%+13.85), and IKDC 2000 (Pre-testing: 66.66%+9.85; Post-testing: 76.05%+14.62) (p<0.032). Administering mechanical perturbation training using compliant surfaces induce effects similar to manual perturbation training on knee functional performance after acute ACL-rupture. The clinical significance is both modes of training improve patients’ functional-performance and limb-to-limb movement symmetry, and enhancing the patients’ self-reported of knee functional measures after ACL rupture. Mechanical perturbation that provides a compliant surface might be utilized as part of the ACL rehabilitation training.

Keywords: Knee Ligament Knee, Clinical Outcomes Research, Hip and Knee Arthroplasty, Surgical Repair and Rehabilitation, Knee, Repair, Therapeutics, Bone Fracture

Introduction

Anterior cruciate ligament (ACL) rupture is a common injury in young athletes who participate in jumping, cutting, and pivoting activities.1 The hallmark symptom of an ACL rupture is dynamic knee instability,2 which affects the ability to perform both daily living and sports activities.3–5 Additionally, ACL ruptures results in quadriceps strength deficits, limb movement asymmetry, and poor knee function that lead to negative consequences during performance of dynamic functional activities.1–4 These poor outcomes may also predispose individuals to a second knee injury and increase the likelihood of developing knee osteoarthritis (OA).8,9

While reconstructive surgery is the preferred management for return to high-level activities, there are specific instances (i.e. early-season sports injury or seasonal laborers) when postponing ACL reconstruction is preferred. In such cases, delayed surgery in the short- or long-term is advantageous, and non-surgical management becomes a viable option to allow patients to resume high-demanding activities without surgery.10,11,40 It is evident that resolving knee impairments, neuromuscular dysfunction, and functional deficits prior to surgery are associated with earlier restoration of knee function and superior outcomes after reconstruction surgery.5,6

The current evidence-based treatment algorithm for patients who plan to pursue non-surgical treatment is perturbation-enhanced rehabilitation.2,14,15 Perturbation training is a type of neuromuscular intervention that improves dynamic knee stability, restores normal knee movement patterns, and enhances knee functional performance.7–10 However, perturbation training is not widely used in the clinical setting due to extensive one-on-one time required for manual delivery of the perturbation.11 Additionally, manual perturbation is limited to stationary standing task while maintaining contact with the perturbation boards. The effect of administering perturbation training with sufficient challenges, simulating real-life perturbations similar to what would occur during dynamic functional activities with hopping and jumping-type manouvres, is yet to be determined.

An automated “Reactive Agility System” (Simbex LLC) with an embedded moveable-plate that provides unanticipated compliant surface by moving in the vertical direction. Previous studies revealed that performing hopping and running on compliant surfaces alters the body mechanics by increasing joint stiffness.12–14 Ultimately, the mechanical device provides a compliant surface that may help patients with ACL rupture develop neuromuscular strategies to stabilize their knee during dynamic functional activities. In addition to compliant surfaces, mechanical perturbation devices have been widely used in rehabilitation programs for patients with different neurological and musculoskeletal impairments.15–19 Mechanical perturbation also helps to restore neuromuscular coordination through controlled and progressive perturbing stimuli.15,16,20 Performing functional activities on mechanical perturbation devices with compliant surfaces may place higher demand on the knee joint, and lead to greater muscle force generation that could improve joint stability.12,13,21,22 To this end, the effectiveness of administrating mechanical perturbation training with compliant surface on dynamic knee stability and the knee function of patients with ACL-rupture has not been investigated. Therefore, the aim of this study was to evaluate whether administration of mechanical perturbation with compliant surface provides effects similar to manual perturbation training on functional performance-based and patient-reported measures in athletes with ACL-rupture.

Methods

Patients with an acute isolated unilateral ACL rupture (< 7months from the injury) between the ages of 14–55 were enrolled into this preliminary prospective cohort (therapeutic) study and completed 10 sessions of mechanical perturbation training involving a compliant surface (Mechanical group) using the Reactive Agility System (Simbex LLC, Lebanon, NH). Patients were matched by age and sex with patients from a prior randomized control study who received manual perturbation training (Manual group).8,23 All patients participated in level I or II activities that included jumping, cutting, pivoting, and lateral movements (e.g. soccer, basketball, football, rugby, field hockey) for > 50 hours per year prior to their ACL rupture.24 Patients with serious lower extremity injury (e.g. fracture), concurrent multiple ligamentous injury or repairable meniscus, osteochondral defect > 1 cm2, or if they demonstrated < 3 mm side to side difference in passive anterior knee laxity measured with a KT-2000 arthrometer25 were excluded from this study. Both physical examination and magnetic resonance imaging (MRI) were used to confirm complete ACL rupture and concomitant knee injuries. The study’s protocol was approved by the University of Delaware’s Institutional Human Subjects Review Board. Patients were recruited from local physician and physical therapy clinics. All patients provided written informed consent for participation in this study.

Training program

Eight patients who were enrolled into this study received mechanical perturbation training on the Reactive Agility System device. The device has an embedded moveable plate that moves in the vertical direction (one-degree of freedom) providing unanticipated translations (compliant surface) (FIGURE 1).

FIGURE 1.

FIGURE 1

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Reactive Agility System with Compliant Surface Plate

The control panel of the device allows changes in the state of the plate so it drops vertically as a compliant surface. The control panel of the device allows three modes of operation (constant rate, random, user-controlled), with the clinician able to control two parameters, the rate at which the plate changes states and the number of times of changing the plate’s state in each trial.

The mechanical perturbation program included 10 sessions of dynamic stabilization training and plyometric training. The pre-testing and training program were administered once patients presented with a resolution of initial impairments after ACL injury (i.e. no knee pain, minimal knee joint effusion as measured with the modified stroke test,26 full knee joint range of motion, and ≥ 70% quadriceps index between limbs). The mechanical training program was divided into three phases. The first phase (session 1–3) included bilateral limbs activities (squat, jumping, jumping jacks, double-legged 45 degree turn jumps, and anterior lunges). During this phase patients performed dynamic stabilization training for three sets of 3o seconds each and 2 sets of 8 repetitions for plyometric training. The second phase (session 4–7) included unilateral limb activities (step down, single-legged squat, star reaching, single-legged chops/lifts, running in place, single-legged hops in place, single-legged hops anterior-posterior and mediolateral, and single-legged hops with 45 degrees turn). Patients completed three sets of 60 seconds of dynamic stabilization training and 2 sets of 10 repetitions of plyometric training. The third phase (session 8–10) included single-legged activities similar to the second phase with the addition of sports-specific activities that included patients tossing or kicking a ball by their hands, heads, or a racquet. Patients completed 3 sets of 60 seconds of dynamic stabilization training and 3 sets of 10 repetitions of plyometric training. The three phases of the mechanical training program were performed on movable plate (compliant surface) of the mechanical device. During the first session, patients were instructed on how to perform the training and were verbally cued on when the plate would drop down. The patients were progressed to more random and unanticipated dropdown of the plate toward the end of the first phase. The dropdown of the plate was unanticipated and could take place during different phases of the activities (i.e. take off, landing, turning, squatting, and standing up from squat). The dropdown displacement (59 mm) and the rate of displacement were similar throughout the three phases of the mechanical training program. Patients were systematically progressed throughout the training program by increasing the difficulty of the training, increasing the time period for each set, increasing the number of repetitions, and by adding sport specific activities. Progression throughout the program was criterion-based similar to that of the manual perturbation training.7 Patients were given rest time after each set to avoid fatigue, with soreness rules being implemented during patients’ progression. Patients’ responses to training were monitored and they were provided with instructions on how to perform the activities appropriately. The complete mechanical perturbation training protocol is outlined in APPENDIX A.

Eight subjects from a previous study8,27,28 were matched by age and sex received manual perturbation training that was previously described by Fitzgerald et al.7 In short, patients in the manual group received perturbation training administered by a therapist and included administration of purposeful manipulation of the support surfaces including three training conditions: rockerboard, rollerboard, and rollerboard and platform by a physical therapist. The mechanical training program was compared to the manual perturbation training because the current physical therapy guidelines recommends administration of a perturbation-augmented training as standard therapy. All patients were tested within two weeks of initiation and completion the training sessions.

Patients in both treatment groups who presented with a quadriceps strength index less than 80% received a supervised, progressive strength training augmented with neuromuscular electrical stimulation (NMES) to improve quadriceps strength. Patients with quadriceps strength index between 80 and 90% received supervised progressive strength training without NMES. Patients with quadriceps strength index more than 90% were instructed to start a strengthening program to improve their quadriceps strength.3

Testing

Patients completed performance-based tests (quadriceps strength and single-legged hop tests29) and patient-reported measures (Knee Outcome Survey-Activities of Daily Living Scale (KOS-ADLS), Global Rating Score (GRS), International Knee Documentation Committee 2000 subjective knee form (IKDC 2000)). Testing was initiated within two weeks prior to the start of the training protocol (Pre-testing) and within two weeks of completion of training (Post-testing).

Performance-based testing

Quadriceps strength was tested during a maximal voluntary isometric contraction (MVIC) on the electromechanical dynamometer (Kin-Com, Chattanooga Corp, Chattanooga, TN)30. Patients were seated with their hip and knee flexed to 90° with the hip, knee, and ankle were stabilized to the seat and dynamometer arm using straps. Patients were instructed to maximally contract their quadriceps muscles. Patients performed 3 practice trials and up to 3 testing trials, with 1 minute rest between trials. Quadriceps index (QI) was calculated as the quadriceps muscle forces of the involved limb to uninvolved limb.

Hop performance was tested using four single-legged hop tests: single hop, cross-over hop, and triple hop for distance, and 6-meter timed hop.29 All patients wore a functional knee brace on the involved limb during hop testing. Two practice trials of each hop test were first completed followed by two measured trials on both limbs, with the uninvolved limb tested first. Hop trials were counted if patients landed on the same leg and demonstrated body balance and control during landing without touching the ground with the other leg. For the single hop, cross-over hops, and triple hops, the two measured trials were averaged and a limb symmetry index (LSI) was computed as the percentage of the hopping distance of the involved limb to the uninvolved limb. For the 6-meter timed hop, LSI was computed as the percentage of the hopping time of the uninvolved limb to the involved limb.

Patient-reported measures

After performance-based testing, patients completed the patient-reported questionnaires that included the KOS-ADLS, GRS, and IKDC 2000. The KOS-ADLS is a 14-item questionnaire that measures patients’ perceptions of the knee symptoms and functional limitations related to the ACL-rupture and how these symptoms and functional limitation affect their ability to perform activities of daily living.31 The KOS-ADLS is a reliable, valid, and responsive measure for assessing functional limitations of the knee, with intraclass coefficients of 0.97 test-retest reliability32. The KOS-ADLS score is reported as a percentage with high score indicates no limitation. GRS is used to evaluate the knee functional performance of patients. GRS consists of one question that asks patients to rate their current knee function on a scale from 0% to 100%. A score of 0% indicates an inability to perform any activity and 100% indicates the ability to perform function as prior to injury, including sporting activities. Analogue GRS has been reported to have a high test–retest intraclass coefficients of 0.96.33 The IKDC 2000 is a knee-specific outcome measure. The IKDC 2000 consists of 18 items that ask questions assessing patients’ symptoms, function, and sport activities relevant to different knee injuries.34 The IKDC 2000 score is reported as percentage of the patients score to the total score, with a higher score indicating good knee function and lower severity of symptoms. The IKDC 2000 is a valid and reliable self-reported outcome measure.34

Statistics

Independent t-test was used to determine differences between groups (Mechanical and Manual) for patients’ demographics, performance-based, and patient-reported at pre-testing session. A 2×2 analysis of variance (ANOVAs) were used to evaluate differences between treatment groups (Mechanical and Manual) and over time (pre-testing and post-testing) for performance-based and patient-reported measures. Bonferroni correction was used to adjust for multiple comparisons (p=0.025) and Eta squared was also used as an indicator for effect size (ES).

Results

Eight patients from the mechanical group completed the study while four patients from the mechanical group did not complete the study; one decided to stop the study for inconvenience of commuting, one patient chose to stop training for academic purposes, one patient dropped and did not return to the follow-up, one patient reported pain during pre-training testing, which excluded the patient from being able to continue participation in the study.

No significant differences were found between groups for the age, time from injury to pre-testing, and BMI (P>0.22). Additionally, no significant differences were found between groups for all performance-based and patient-reported measures at pre-testing (p>0.18) (TABLE 1).

TABLE 1.

Patient’s Demographic, Performance-Based, and Patient-reported Measures Of Manual and Mechanical Groups At Pre testing (Mean (SD)).

Variables Manual group (n=8) Mechanical group (n=8) P-value
Patients #(women/men) 8 (4/4) 8 (4/4) 1.00
Age (year) 33.50 (13.21) 33.50 (13.42) 1.00
BMI (kg/m2) 29.25 (7.25) 25.70 (3.03) 0.22
Time from injury to pre-testing session (Week) 5.67 (6.30) 9.14 (6.65) 0.33
Injured side (Right/Left) (4/4) (6/2) 0.30
QI (%) 89.25 (10.16) 92.39 (16.63) 0.66
Single hop LSI (%) 78.75 (22.59) 87.49 (17.59) 0.40
Cross-over hop LSI (%) 74.00 (29.21) 89.82 (16.32) 0.21
Triple hops LSI (%) 78.86 (16.62) 88.58 (9.47) 0.18
6-m timed hops LSI (%) 86.86 (12.83) 93.77 (18.01) 0.41
KOS-ADLS (%) 81.38 (6.76) 80.89 (14.20) 0.93
GRS (%) 71.88 (17.92) 65.38 (13.19) 0.42
IKDC 2000 (%) 69.39 (9.09) 63.94 (10.55) 0.29
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QI: Quadriceps index; LSI: Limb symmetry index; KOS-ADLS: Knee Outcome Survey-Activities of Daily Living Scale; GRS: Global Rating Score; IKDC 2000: International Knee Documentation Committee 2000

There were no significant group-by-time interactions for performance-based and patient-reported measures (p>0.19) (Table 2). Main effects of time were found for single hop LSI (Pretesting: 85.14%+21.07 Post-testing: 92.49%+17.55; p=0.019, ES:0.38), triple hop LSI (Pretesting: 84.64%+14.17; Post-testing: 96.64%+11.14; p=0.029, ES: 0.37), KOS-ADLS (Pretesting: 81.13%+11.12; Post-testing: 88.63%+12.63; p=0.005, ES: 0.44), GRS (Pre-testing: 68.63%+15.73; Post: 78.81%+13.85; p=0.032, ES: 0.29), and IKDC 2000 (Pre-testing: 66.66%+9.85; Post-testing: 76.05%+14.62; p=0.01, ES:0.38).

TABLE 2.

Performance-Based And Patient-Reported Measures Of Manual And Mechanical Groups At Pre- And Post-Testing (Mean(SD))

Pre-Testing Post-Testing
Variables Manual
(n=8)		 Mechanical
(n=8)		 Manual
(n=8)		 Mechanical
(n=8)		 Group*Time
(p-value) (ES)
QI (%) 89.25 (10.17) 95.53 (15.60) 91.00 (9.91) 98.25 (14.38) 0.85
(0.003)
Single Hop LSI (%) 78.75 (22.59) 91.53 (18.09) 82.50 (20.58) 102.47
(11.43)		 0.21
(0.13)
Cross-over hop LSI (%) 72.67 (31.76) 94.57 (14.96) 88.67 (10.46) 101.12
(14.38)		 0.55
(0.04)
Triple hop LSI (%) 78.86 (16.62) 90.42 (10.42) 92.00 (12.38) 101.28 (9.44) 0.81
(0.005)
6-m timed hop LSI (%) 86.86 (12.83) 89.75 (6.63) 94.57 (9.57) 95.21 (5.55) 0.77
(0.008)
KOS-ADLS (%) 81.38 (6.76) 89.75 (6.90) 80.89 (14.20) 87.50 (16.48) 0.70
(0.01)
GRS (%) 71.88 (17.92) 65.38 (15.19) 76.25 (9.54) 81.38 (17.10) 0.19
(0.12)
IKDC 2000 (%) 69.39 (9.09) 63.94 (10.55) 74.38 (10.46) 77.73 (17.83) 0.20
(0.12)
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ES: Effect size for group-by-time interaction; QI: Quadriceps index; LSI: Limb symmetry index; KOS-ADLS: Knee Outcome Survey-Activities of Daily Living Scale; GRS: Global Rating Score; IKDC 2000: International Knee Documentation Committee 2000

Discussion

The results of this preliminary study indicate that administering mechanical perturbation training with compliant surface induces effects similar to manual perturbation training on knee functional performance and patient-reported measures after an acute ACL rupture. The findings of this study indicate that patients in both groups improve their knee functional performance and scored higher on self-report measures after training regardless of the perturbation type.

In this study, performance-based and patient-reported measures were used to compare the efficacy of two types of perturbation training. Both groups improved their knee functional performance and restored limb-to-limb hop symmetry. Both training groups demonstrated almost a moderate improvement effect on the performance-based measures after training. The hop tests consist of movement-specific tasks involving jumping, pivoting, and landing maneuvers similar to those found in high-risk physical activities.29 These tests have been used as testing tools for assessing dynamic knee stability and they have the ability to detect patients’ changes in response to different therapeutic intervention.2,27 The improvements of the hop performance and limb-to-limb movement symmetry most likely resulted from the training programs as both training focus mainly on rehabilitating the injured limb. In this study, the mechanical group demonstrated a higher, but not statistically significant, functional performance compared to the manual group at pre-testing. The data of this study does not explain of why, knowing that these differences did not reach a significant level at a p-value of 0.05. The high performance of the mechanical group may have had an effect on the results of this study, as mechanical group may have demonstrated a ceiling effect. Nonetheless, restoring limb-to-limb movement symmetry indicates that patients are able to restore physical capacity of the involved limb during functional tasks similar to that of the uninvolved limb. Further, limb-to-limb hop symmetry indicates that the injured limb was rehabilitated adequately to withstand the physical demand of high-risk physical activities. These finding were also supported by the patient-reported measures as patients in both groups scored higher on the patient-reported measures after training. It could be detrimental for patients to performing high-risk physical activities with the presence of limb-to-limb asymmetry, as limb-to-limb asymmetry may become magnified during physical activity that can increase the risk of knee re-injury.35,36 These types of injuries could be manifested as overloading the uninjured limb that might cause overuse injuries, or as under loading the injured limb that may be associated with early radiological knee osteoarthritis.37

The results of this study also revealed that administering mechanical perturbation training including compliant surface provided effects similar to manual training on patient-reported measures. The results of this study showed that patients in both groups scored higher on patient-reported measures after training with almost a moderate improvement effect was achieved, regardless of the perturbation type. Patients in both groups demonstrated higher self-satisfaction about their knee functional performance after training. This might have resulted as knee symptoms and functional limitations due to the ACL-rupture had less impact on the performance of daily living and functional activities. Patients also reported better perception of their knee function after training. This resulted from the training programs as patient received progressive rehabilitation training that helped with resolving the knee symptoms and impairments.

One challenge of this study was that the training programs were different. Training setups, modes of perturbation stimuli, and type of activities that were performed in each program may account for difference between programs. Nonetheless, the training programs share similarity as they are both used for training the neuromuscular system in attempt to improve patients’ functional performances. In this study, manual perturbation was used as a comparison group as it is the recommended therapeutic intervention for patients opting for non-surgical management after ACL injury. In the manual perturbation, patients maintained a static standing position and were instructed to react to the perturbation stimuli during two techniques: roller board and roller board and platform, while the perturbation stimuli were executed in different directions (anterior, posterior, side-to-side, diagonal, and rotational translations) in the horizontal plane. Furthermore, perturbation training included a rockerboard technique that provides anterior-posterior, side-to-side and diagonal tilting. In comparison, the mechanical perturbation used in this study included performing multiple physical activities (i.e. squatting, jumping, landing, pivoting, running) on a plate that provides an unanticipated translation only in one direction (vertical direction). One advantage of mechanical perturbation with a compliant surface is that the perturbation stimuli can be executed at a time-specific point of different phases during functional activities. These stimuli can simulate real-life perturbations, similar to that occur during dynamic functional activities to improve the neuromuscular responses that can stabilize the knee joint during functional activities. Another advantage of using mechanical perturbation training with compliant surface is that it requires less one-on-one time during training, and it requires less physical labor of the therapist that is required during manual perturbation training. Further studies may consider investigating the changes in joint biomechanics and muscle activities during administration of mechanical perturbation training for patients with ACL rupture.

There are limitations associated with this is preliminary with only 8 patients included in each treatment group. Therefore, the results of this preliminary study cannot be generalized as further studies with larger sample size need to be conducted to confirm our findings. Further, the data of this study does not provide enough information to whether mechanical perturbation with compliant surface should replace the manual perturbation or whether they can be both used to augment an ACL rehabilitation program. Further studies may investigate the effect of implementing both the manual perturbation training augmented with mechanical perturbation training. Additionally, this preliminary study included only Level I or II patients with an ACL rupture, therefore the results of our study cannot be generalized for patients with ACL reconstruction or those who participate in lower level 3 or 4 activities. LSI was used to evaluate the patients’ responses to the therapeutic interventions or knee functional improvement of the involved limb in comparison to the uninvolved limb. Therefore, LSIs may lead to misinterpretation of the results as it is possible that both the involved and uninvolved limbs improve their performance after intervention.38–40 Other limitations are that the results of this study indicate that the groups showed improvement in limb-to-limb movement symmetry; however the results were reported as groups’ means for the hop LSIs. This analysis has a limitation as it does not account for limb-to-limb asymmetry of each individual patient. Further, it does not show the direction of change in limb-to-limb symmetry as there might be patients who may demonstrate more asymmetry.

Conclusion

Administrating mechanical perturbation training that provides an unanticipated compliant surface induces effects similar to the manual training on knee functional performance and patient-reported measures of patients with an acute ACL rupture. Both training types improve knee functional performance and limb-to-limb movement symmetry during functional activities, and enhanced the patients’ self-reported outcome on knee symptoms and function. Implementing unanticipated mechanical perturbation training with a compliant surface into the clinical sitting may help improve dynamic knee stability and knee functional performance outcomes with less one-on-one time and physical labor form the therapist. Further, mechanical perturbation training has potential as a treatment intervention to manage patients after ACL injury.

Acknowledgments

This pilot study was funded by Simbex LLC (www.simbex.com) through the Small Business Innovation Research (SBIR) program and Small Business Technology Transfer (STTR) (R44HD068054). All authors certify that there were no affiliations with or financial involvement in any organization or entity with a direct financial interest in the subject matter or materials discussed in the manuscript. We thank the University of Delaware Physical Therapy clinic (http://sites.udel.edu/ptclinic/) for facilitating the patient management and data collection, and Angela Smith, Martha Callahan, and Karen Ewing for research coordination.

APPENDIX A: MECHANICAL PERTURBATION TRANING PROGRAM

Dynamic Stabilization Training
Exercise Sessions 1–3 Sessions 4–7 Sessions 8–10
3 sets of 30 secs each 3 sets of 60 secs each 3 sets of 60 secs each
Double legged squats    
Anterior lunges    
Jumping jacks    
Step downs    
Single legged squats   w/sports-specific task
Star Reaching   w/sports-specific task
Single-legged chops/lifts   w/sports-specific task
Plyometric Training
Exercise Sessions 1–3 Sessions 4–7 Sessions 8–10
2 set × 8 reps each 2 set × 10 reps each 3 set × 10 reps each
Double legged jumps in place    
Double legged jumps (AP, ML)    
Scissor jumps    
Double legged ¼ turn jumps    
Running in place    
Single legged hops in place   w/sports-specific task
Single legged hops AP, ML   w/sports-specific task
Single legged hops ¼ turn   w/sports-specific task
Drop jumps    
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Footnotes

†

This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: [10.1002/jor.23784]

Contributors: ZN, DL, and LSM conceived the idea of this study. ZN and MF conducted the testing and training of participants. ZN analyzed and interpreted the data. All authors contributed to the writing of the manuscript. All authors contributed to the rebuttal and revised the final draft of this manuscript.

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