Athletic Training and Sports Health Care

Original Research 

Cross-over Effect of Balance Training After Knee Surgery: A Pilot Study

Layci J. Harrison, PhD, LAT, ATC; Lindsey K. Lepley, PhD, ATC; Dana K. Fuller, PhD; Jennifer L. Caputo, PhD, CSCS, MX

Abstract

Purpose:

To evaluate cross-over effect balance training after knee surgery.

Methods:

Individuals with a history of knee surgery (N = 10) were randomized to balance training or control groups. The non-surgical leg was trained three times a week for 6 weeks. Stability of surgical and non-surgical limbs was measured using the Biodex Balance System (BBS) (Biodex Medical System, Inc., Shirley, NY) and the Overall Stability Index. Dynamic postural control was assessed with the Y-Balance Test (YBT).

Results:

Stability and dynamic postural control increased in the untrained surgical leg after training the non-surgical leg (BBS eyes open: P = .023, Cohen's dt1–t3 = 2.68 strong; YBT: P = .030, Cohen's dt1–t3 = −1.59 strong). Balance was not significantly different between legs, but did trend toward improvement (BBS eyes open: Cohen's dt1–t3 = 1.66 strong; YBT: Cohen's dt1–t3 = −1.73 strong).

Conclusions:

Cross-over effect training increased stability and dynamic postural control in the untrained leg. These initial findings support cross-over effect training for balance rehabilitation after knee surgery.

[Athletic Training & Sports Health Care. 2019;11(5):234–242.]

Abstract

Purpose:

To evaluate cross-over effect balance training after knee surgery.

Methods:

Individuals with a history of knee surgery (N = 10) were randomized to balance training or control groups. The non-surgical leg was trained three times a week for 6 weeks. Stability of surgical and non-surgical limbs was measured using the Biodex Balance System (BBS) (Biodex Medical System, Inc., Shirley, NY) and the Overall Stability Index. Dynamic postural control was assessed with the Y-Balance Test (YBT).

Results:

Stability and dynamic postural control increased in the untrained surgical leg after training the non-surgical leg (BBS eyes open: P = .023, Cohen's dt1–t3 = 2.68 strong; YBT: P = .030, Cohen's dt1–t3 = −1.59 strong). Balance was not significantly different between legs, but did trend toward improvement (BBS eyes open: Cohen's dt1–t3 = 1.66 strong; YBT: Cohen's dt1–t3 = −1.73 strong).

Conclusions:

Cross-over effect training increased stability and dynamic postural control in the untrained leg. These initial findings support cross-over effect training for balance rehabilitation after knee surgery.

[Athletic Training & Sports Health Care. 2019;11(5):234–242.]

Restoration of balance after knee surgery is imperative because it is a critical component of joint stability.1 Consequently, the National Strength and Conditioning Association (NSCA) has developed a knee-specific balance training program that can be used for injured or healthy individuals.2 The NSCA protocol includes static and dynamic movements and rhythmic stabilization, also known as perturbations. Perturbations increase the likelihood of an individual returning to high-level activity compared to balance training alone.3 Although postoperative balance and perturbation training have been shown to increase balance ability,4,5 advanced balance training is typically not introduced until later in the rehabilitation process once the individual has returned to full weight bearing to prevent postoperative complications.6 Cross-over effect training, which is unilateral limb training resulting in bilateral adaptations, may be a viable option to introduce balance training earlier in the rehabilitation process without hindering the recovery of the surgical limb.

The cross-over effect is a training phenomenon that has been studied since the 1800s by using unilateral training to positively affect the contralateral limb.7 It is believed that the cross-over effect can increase strength to the contralateral limb by primarily influencing neural adaptations and activation patterns of agonist, antagonist, and synergistic muscles.8–10 Multiple knee surgeries have been linked to a depressed neural environment in the affected joint that can lead to functional deficits years after surgery11,12; therefore, individuals with a history of knee surgery provide an interesting and untested cohort to test the cross-over effect theory with balance training.

Although the complete physiological underpinnings of the cross-over effect are still not understood, a few general conclusions have been reached. A cross-over of strengthening does occur, but there is no change in muscle cross-sectional area in the untrained limb,13 reinforcing that the benefits of cross-over effect training are primarily neural.8,13 Contraction type (eccentric, concentric, or isometric) must be specific to the goal of the exercise program and the muscle group exercised,14 and it takes at least 5 weeks to see adaptations in the unexercised limb.15 Given the inherent neural benefit of cross-over effect training, this type of therapy could help to expedite the rehabilitation process and decrease bilateral deficits, but current research on the cross-over effect of balance is limited, with only two studies investigating this type of therapy on balance outcomes and reporting inconclusive results.10,16 To extend previous research, we sought to conduct a preliminary study on the cross-over effect of balance training in a patient population with a history of knee surgery because patients with a history of knee injuries often have a depressed neural environment.17 Therefore, the purpose of this pilot study was to evaluate the effect of 6 weeks of the NSCA's balance training protocol on the non-surgical leg of participants with a history of knee surgery to examine the cross-over effect of balance ability to the surgical untrained leg. By studying a chronic knee surgery group, we hoped to evaluate the efficacy of using this rehabilitation technique to improve balance. It was hypothesized that training would lead to increases in balance ability in both the trained and untrained legs.

Methods

This study examined the effects of 6 weeks of unilateral balance training on stability and dynamic postural control of both the non-surgical trained and surgical untrained leg.

Participants

Individuals (N = 10) who had knee surgery (anterior cruciate ligament [ACL] reconstruction, partial meniscectomy, meniscal transplant surgery, and meniscus repair) in the past 8 years were randomly assigned, via a random number drawing, to the training or control group. Participants were excluded if they had any physical limitations due to surgery that prevented them from completing activities of daily living, had bilateral surgeries, were participating in therapy for the surgery, suffered an acute lower body injury prior to or during training, or had any visual or vestibular deficits. Informed consent was collected from all participants and the study was approved by the Middle Tennessee State University Institutional Review Board.

There were 5 participants in the training group (2 women and 3 men; mean age: 23.8 ± 5.4 years; height: 175.0 ± 7.7 cm; mass: 80.4 kg; months postoperative: 63.0 ± 32.3) and 5 participants in the control group (3 women and 2 men; mean age: 23.2 ± 4.0 years; height: 172.6 ± 8.0 cm; mass: 90.6 ± 12.6 kg; months postoperative: 33.0 ± 13.0). Before intervention scores on the Marx Scale, Knee Outcome Survey–Activities of Daily Living Scale (KOS-ADLS), and Sports Activity Scale (SAS) were 12.6 ± 3.6, 96.5% ± 3.0%, and 94.9% ± 4.5%, respectively, for the training group and 5.8 ± 3.7, 95.4% ± 4.1%, and 93.1% ± 4.7%, respectively, for the control group. Table 1 lists the surgical intervention and before intervention Biodex Balance System (BBS) (Biodex Medical System Inc., Shirley, NY) and Y-Balance Test (YBT) scores.

Participant Demographics (Mean ± SD)

Table 1:

Participant Demographics (Mean ± SD)

Regardless of group, dynamic postural control was measured using the Y-Balance Test (YBT) and stability was measured using the BBS before, during, and after the intervention.

Testing Protocol

All participants reported to the exercise science laboratory at least three times during the 6-week study for balance assessments. The control group reported on three separate occasions (weeks 1, 3, and 6) for balance assessments and the training group attended 18 training sessions in addition to three balance assessment sessions. Height, body mass, and leg length were measured and age was reported prior to testing. All participants completed balance testing, a physical activity questionnaire, and two knee function assessments before, during, and after the intervention. The KOS-ADLS and KOS-SAS18 were used to measure knee function. The Marx Scale19 was used to measure physical activity levels. Balance testing consisted of the YBT to measure dynamic postural control. The Dynamic Balance Assessment bilateral comparison on the BBS was used to measure stability via the Overall Stability Index (OSI).20 Testing procedures and starting limb were counterbalanced by participant, with the first participant starting balance assessments on the limb without a history of knee surgery and completing the YBT followed by the BSS and the next participant starting the balance assessments with the limb with a history of surgery and the BSS followed by the YBT.

Training Protocol

Balance training was completed by participants in the training group only on the non-surgical limb and consisted of three sessions per week for 6 weeks for a total of 18 sessions. All exercises were completed in an exercise science laboratory. Each session was separated by at least 24 hours. All balance training exercises followed the NSCA's balance training protocol including single leg stances, lunges, and hops.2 Training progressed every 2 weeks from a solid surface to a foam pad to a Bosu ball (Bosu, Ashland, OH). The training protocol is outlined in Table 2. The compliance rate for training was 100%.

Balance Training Protocol

Table 2:

Balance Training Protocol

Stability Measurements

The BBS measures average angular displacement from the center by allowing 20° of movement in all directions.20 The BBS measures changes in tilt in a medial lateral and anterior posterior axis, is believed to provide specific information on joint movement,21 and has been used to identify stability differences and test the effectiveness in balance training after ACL reconstruction.1,22 The main outcome (OSI) represents the variance of platform displacement in degrees from level in both the anterior posterior and medial lateral directions.20 The OSI is calculated using the following formula20,21:

OSI=∑(O−Y)2+(O−X)2#samples

where Y represents the variance in anterior posterior stability and X represents the variance in medial lateral stability. A high number represents difficulty maintaining balance, whereas a low number shows the ability to maintain stability.20 Reliability studies on the OSI have shown it to be a reliable measurement of balance.23

Participants maintained the same starting limb for each assessment, first with eyes open (BBSEO) and then with eyes closed (BBSEOC). All assessments were completed on a stability level of 1; the most unstable platform of the device ensures variability of scores with this young active population. Prior to beginning the test, the platform was released and the participant was instructed to attempt to balance on the testing limb and find the most comfortable foot position where the center of balance could be maintained. The coordinate of the foot position was recorded and used during and after intervention testing. The platform was then locked. At the start of the test, the platform was unlocked and a 5-second countdown cued the participant on the start of the test. Participants were instructed to keep their hands on their hips and their free foot at least 5 cm from the platform while maintaining single leg balance. If a participant started to lose balance, he or she was told to grab the handrails and quickly regain balance. At the end of each trial, the platform locked and the OSI was recorded. Participants completed at least three trials, with 30 seconds of rest between trials. If the participant's stability index continued to decrease, additional trials were completed until a plateau in scores was reached, indicating the score/stability was no longer improving. The lowest OSI for each condition was used in the analysis.

Dynamic Postural Control

We used the YBT to measure dynamic postural control, which is frequently used to predict lower extremity injuries and determine return to play after injury.24 The YBT includes three axes. The posterior axes are separated by 90° and the anterior axis is separated from both posterior axes by 130°. Each axis is equipped with a sliding platform and measuring tape. Prior to beginning the baseline YBT, leg length was measured on each limb in centimeters to the nearest tenth from the anterior iliac spine to the distal aspect of the medial malleolus. Next, the participant was instructed to stand on the center platform with the great toe aligned to the intersection of the axes and hands placed on the hips. Without shifting weight, the participant was instructed to bend the supporting leg's ankle, knee, and hip and, without lifting the heel, to reach the contralateral leg as far as possible and push the platform along each axis. The researcher recorded each reach in centimeters to the nearest tenth. The process was repeated four times. Although a specific familiarization session was not used, if participants continued to increase reach after the fourth trial, that specific direction was repeated until a plateau was reached. In most cases, participants reached a plateau by trial 4. The same process was repeated on the opposite limb. The longest reach for each direction was summed and then normalized by the reaching leg's supine length to create a composite score for each leg.

Physical Activity and Functional Assessments

Participants were asked to maintain consistent physical activity levels throughout the duration of the 6-week protocol. Physical activity was assessed before, during, and after the intervention. The Marx Scale was used to measure knee-specific physical activity relative to the frequency of running, cutting, decelerating, and pivoting. Participants selected from less than one time a month, one time a month, one time a week, two to three times a week, or four or more times a week for each question. The Marx Scale has good reliability (interclass correlation coefficient of 0.97) and correlates well with other activity rating scales.19

The KOS-ADLS and KOS-SAS contains a total of 25 questions. The ADLS portion measures function during ADL,25 whereas the SAS is used to assess a higher level of physical function.18 The first 17 questions are specific to ADL. Participants rated the difficulty of performing each ADL from 5 (no difficulty) to 0 (unable to perform). Answers were summed, divided by 70, and multiplied by 100 to create a percentage score to represent functional ability.18 The remaining 11 questions on the scale are specific to recreational and sport-specific activities. Participants responded to each question using the same Likert scale. Answers were again summed, divided by 55, and then multiplied by 100 to create a percentage indicating physical function. The KOS scale is a reliable and valid measurement of knee function according to an interclass correlation greater than 0.8.26–28

Statistical Analysis

Repeated-measures analyses of variance (ANOVA) were used to ensure physical activity levels remained constant and to assess the functionality of the surgical knee over the 6 weeks via symptom scores on the KOS-ADLS and KOS-SAS. To determine the effect of balance training on stability and dynamic postural control, the trained non-surgical limb was compared to the non-surgical limb of the control group using a 2 × 3 (group × time) repeated-measures ANOVA. To determine the magnitude of the cross-over effect, a 2 × 3 repeated-measures ANOVA was used comparing stability and dynamic postural control of the surgical untrained leg in the control and training groups. A familywise alpha value of .05 was used. Sidak pairwise comparisons were used when a significant interaction was found. Due to a small sample size, Cohen's d effect sizes were calculated to examine trends toward significance using the following formula: (Cohen's d = [pre-intervention − post-intervention] / pooled standard deviation). According to Cohen, a weak effect size is assumed for values below 0.5, moderate effect for values between 0.5 and 0.79, and a strong effect for values 0.8 and above.27

Results

Intervention Compliance and Patient Demographics

There was no difference in participant age (t8 = −0.20, P = .846), height (t8 = −0.49, P = .639), body mass (t8 = 0.90, P = .369), or months postoperative (t8 = −1.93, P = .090) between groups, suggesting successful randomization. Two-way repeated-measures ANOVAs with group (control, training) as the between-subjects factor and time (before, during, and after intervention) as a within-subjects factor were used to examine changes in the dependent variables. Table 3 lists the statistical results. The Sidak procedure (familywise alpha = .05) was used to conduct pairwise comparisons. There were no interactions between group and time for physical activity or symptom levels from between before, during, and after intervention, meaning there was no difference over time in physical activity or surgical knee symptoms between the training and control groups.

Repeated Measures Analysis of Variance Interactions

Table 3:

Repeated Measures Analysis of Variance Interactions

Effects of Balance Training on the Untrained Leg

There was a significant interaction between group and time for the stability (OSI) via the BBSEO of the untrained surgical leg showing that stability (OSI) did respond differently with cross-over effect limb training versus no training (Table 4). Stability was better after the intervention than before the intervention for the training group and not the control group. Effect sizes were strong with the untrained leg in the training group and, with the exception of the mid-intervention measurement, effect sizes were weak for the control group (Table 4). Stability measurements via the BSSEOC showed no interactions for the trained or untrained leg, but effect sizes were moderate and strong for the training group and weak for the control group (Table 4).

Average Stability Measurements on BBS (Mean ± SD)a

Table 4:

Average Stability Measurements on BBS (Mean ± SD)

The untrained leg showed a significant interaction between group and time for dynamic postural control as measured by the YBT. Sidak pairwise comparisons showed an increase in dynamic postural control of the untrained surgical leg between before and after measurement times for the training group and not the control group. The untrained leg also showed a strong effect between the during and after intervention and before and after intervention measurements and weak effect sizes in the control group. Means for the dynamic postural control can be found in Table 5.

Average Dynamic Postural Control Measurements on YBT (Mean ± SD)a

Table 5:

Average Dynamic Postural Control Measurements on YBT (Mean ± SD)

Effects of Balance Training on the Trained Leg

When evaluating stability (OSI) with the BBS, there was not a significant interaction between group and time with eyes open or eyes closed assessments for the trained leg (Table 4). Although there was not a significant difference between groups, effect sizes were strong for all three measurements in the training group, meaning there was a trend toward OSI improving with balance training. In contrast, effect sizes for the control group were much smaller (Table 4).

For dynamic postural control (YBT), there was not a significant interaction between group and time for the trained leg, but effect sizes for during to after intervention and before to after intervention were strong for the training group and weak for the control group, with the exception of during to after intervention measurement, in which it was moderate (Table 5).

Discussion

The purpose of our pilot study was to determine the effect of the NSCA's balance training protocol on stability and dynamic postural control of the trained leg and to examine the presence and magnitude of cross-over effect in the untrained surgical leg of patients with a history of knee surgery after 6 weeks of balance training. The goal was to determine whether training the non-surgical limb would result in a cross-over in the surgical limb, allowing the development of early rehabilitation techniques for safely restoring or maintaining balance ability after knee surgery. Increases in proprioception after balance training are correlated with functional ability and joint stability, and are necessary for return to sport after knee surgery.1 The main finding of our work was that balance training the non-surgical leg led to increased stability and dynamic postural control for the untrained surgical leg in the training group (Tables 35), partially supporting the initial hypothesis. Although we did not see increases in self-reported functional ability from the KOS-ADLS and KOS-SAS, we did see a positive trend toward an increase in balance ability after training both the trained and untrained limbs of the training group (Table 3). Eight weeks of balance and agility training three times per week has been shown to increase scores on the KOS-ADLS in individuals with osteoarthritis,27 but the lack of increased functionality in this study (decreased symptoms) may be because our participants were already functioning at a high level or too short of a training intervention was used. Most participants were involved in recreational sports and reported minimal symptoms related to the knee surgery (Table 1).

Balance training is useful during the rehabilitation process to improve functional outcomes and prevent reinjury.29 Notably, individuals can suffer from balance deficits from 30 months to 20 years after ACL reconstruction.1,30 Starting balance training early in the rehabilitation process could negate some of the lasting balance deficits. Due to safety concerns, many researchers do not start balance training until 9 to 16 weeks postoperatively.6 In some cases, initiating balance training on the surgical limb as soon as 4 weeks after ACL reconstruction was not sufficient to elicit significant differences in balance ability between before and after intervention after 12 sessions of training.4 This lack of improvement may be due to low intensity balance training due to safety concerns for the injured limb.

Although ACL reconstruction is the most commonly researched injury with balance training, partial meniscectomies also induce neuromuscular complications.11 Therefore, as part of our pilot work, we included ACL reconstruction, partial meniscectomy, meniscal transplant surgery, and meniscus repairs to study the overall effect of cross-over effect training on knee injuries, which can be examined with greater case sensitivity in future studies. Notably, despite the varied sample of knee injuries and the unbalanced distribution of surgery type by group included in our work, we did find that balance ability improved in the surgical limb (Tables 35), suggesting the promising ability of cross-over effect training to enhance function after meniscal injuries, with the possibility of being a valuable technique for a wide range of knee patients.

Although well researched with eccentric, concentric, and isometric strength training, the presence of a crossover effect for balance training has not been confirmed in a population with a history of knee surgery. Unilateral balance training has been shown to enhance responses to perturbations bilaterally after 6 weeks of progressive perturbation training in healthy individuals.10 However, few studies have investigated the ability of cross-over effect training to enhance measures of balance in knee injury populations. For the first time, we investigated the benefits of cross-over effect training in participants with a history of knee surgery. A strength of our work is the use of laboratory (OSI) and clinical (YBT) measures that help to confirm our results (Tables 45). We specifically chose to use the YBT because this test is frequently used clinically to assist in making return to play decisions.24 Hence the YBT may be a clinical test that rehabilitation specialists can use to track beneficial changes in their patients in response to cross-over effect balance training.

Cross-over effect training is believed to work by primarily influencing neural adaptations that are thought to be disrupted after major knee injury or surgery. Damage to the mechanoreceptors after injury is often cited as a source of muscle inhibition because this damage can alter afferent messages from the receptors, which, in turn, can alter the efferent messages to the quadriceps and decrease muscle activation.31 Muscle inhibition has been shown to affect an injured limb years after both ACL surgeries and partial meniscectomies.11,12 Emerging evidence also suggests that major knee joint injuries such as ACL rupture can affect brain activation.32 Hence negative adaptations in peripheral and central nervous systems can affect muscle function and overall functionality. To date, cross-over effect training is thought to enhance function by primarily influencing brain networks.33,34 Future work that investigates the ability of cross-over effect therapy to enhance balance via nervous system adaptations will need to measure brain activity (functional magnetic resonance imaging, transcranial magnetic stimulation, or electroencephalogram) and spinal excitability (Hoffman reflex)35 to better understand the neural adaptations that may lead to balance improvements.

Six weeks of single leg balance training did not significantly increase the stability or dynamic postural control of the trained non-surgical leg, but strong effect sizes showed a trend toward improvement. We speculate that the lack of significant results is driven by the little room for improvement because functionality in the contralateral uninjured limb was greater at the start of the intervention (Tables 45). Our effect sizes support the work of Vathrakokilis et al.,1 which showed that single leg balance training that occurs three times a week for approximately 20 minutes can likely improve the balance ability of the trained leg. Although not significant, when referring to Table 4 it appears that BBS scores on the trained leg decreased, showing improvement in stability, whereas the control group scores remained consistent. It is also important to note that some participants responded to the training within the first 3 weeks, whereas others did not show changes until the end of the 6 weeks of training. In our study, all participants progressed every 2 weeks regardless of their adaptations to the balance training, which may have altered how some of the participants responded. Notably, there may have been a learning curve on the BBS. Although all tests were performed to a plateau, it is possible that a learning curve affected the results on the trained non-surgical leg. A familiarization session was not conducted, but reliability measurements were followed for both the BBS and YBT by completing at least three and four trials, respectively, to produce a reliable test.23,24 The addition of a familiarization session may be a way to guard against a learning curve. In addition, most researchers suggest at least 6 weeks of knee-specific balance training to see an effect.2 It is possible that a longer training protocol would have better illustrated the cross-over outcomes of the balance program.

We conducted a small randomized controlled trial to examine cross-over effect balance training in a population with a history of knee surgery. Although we had a small sample size, the work is promising. Given that this study is the first of its kind, to our knowledge, we primarily used effect size calculations to determine whether this training had a positive effect. Because of the strong effect size demonstrated in all assessments, we suggest further research with more participants with a specific focus on one type of knee pathology. Furthermore, although participants were randomly assigned to groups, the training group consisted of participants who had experienced ACL reconstruction and the control group consisted of participants with mainly meniscectomy. Although the cross-over of balance ability of an extensive surgery such as ACL reconstruction is notable, we suggest further research with groups matched for surgical history. Finally, although the KOS-ADLS and KOS-SAS scores did not improve in this sample, they may improve in a sample that is functioning at a low level. If the individual is at a high level of function, we suggest using a different functional measurement scale.

Implications for Clinical Practice

We safely implemented a 6-week balance training program on the non-surgical leg of individuals with a history of knee surgery. Because knee surgery typically results in immobilization or limited weight bearing, our study suggests simple balance training with limited equipment on the non-surgical leg may be a way to decrease the protracted balance deficit commonly present after surgery. Based on our results, we conclude that 6 weeks of progressive balance training following the NSCA's protocol three times a week lasting 30 minutes is effective in causing a cross-over of balance ability to a knee after ACL reconstruction, partial meniscectomy, meniscal transplant surgery, or meniscus repair. It must be noted that our study results are from individuals at least 1 year after surgery and further research is needed to determine an optimal time to begin cross-over effect training. Rehabilitation specialists should consider incorporating cross-over effect training to safely improve balance after knee surgery.

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Participant Demographics (Mean ± SD)

Group Surgical/Limb Postop (mo) Dominant Limb Before Intervention (Surgical Limb/Non-surgical Limb)

BBSEO BBSEC YBT
Training
  1 ACL reconstruction, meniscectomy/L 48 R 7.9 ± 10.8 11.3 ± 11.4 78.4 ± 83.3
  2 ACL reconstruction/R 16 R 12.7 ± 4.4 17.6 ± 17.4 87.9 ± 94.1
  3 ACL reconstruction, meniscus repair/R 101 R 10.8 ± 9.9 10.1 ± 8.3 84.3 ± 91.5
  4 ACL reconstruction, meniscus repair/R 75 R 5.2 ± 4.6 10.3 ± 10.6 97.3 ± 96.1
  5 ACL reconstruction, meniscectomy/L 75 R 8.3 ± 7.2 12.3 ± 14.3 87.7 ± 91.9
Control
  1 Meniscus repair/L 25 R 11.1 ± 11.4 14.3 ± 13.9 86.8 ± 91.5
  2 ACL reconstruction/L 38 R 6.3 ± 4.2 5.2 ± 4.7 82.1 ± 81.7
  3 Meniscus repair/L 50 R 7.4 ± 10.8 14.9 ± 16.6 95.0 ± 100.2
  4 Meniscectomy/L 36 R 4.8 ± 6.4 9.3 ± 9.3 85.8 ± 86.8
  5 ACL reconstruction, collateral ligament repair, meniscus repair/R 16 R 8.1 ± 8.4 9.3 ± 8.8 79.3 ± 76.8

Balance Training Protocol

Exercise Number of Repetitions or Duration Visual
SL stance 3 1-minute bouts EO & EC
SL balance with perturbations delivered by the researcher via a Theraband® on the contralateral leg 3 1-minute bouts EO & EC
Forward lunges with the NS leg forward 3 × 10 repetitions EO
SL hop forward—must stick the landing before placing the contralateral foot on the ground 3 × 10 repetitions EO
SL hop forward—must stick the landing while catching a ball before placing the contralateral foot on the ground 3 × 10 repetitions EO

Repeated Measures Analysis of Variance Interactions

Assessment Degrees of Freedom F Value MSE H-F P η2P
Marx 2, 16 3.22 2.00 .067 .287
KOS-ADLS 2, 16 1.13 23.95 .347 .124
KOS-SAS 2, 16 0.95 4.48 .407 .106
BBS trained leg EO 2, 16 3.22 3.14 .065 .290
BBS untrained leg EO 2, 16 4.18 1.85 .023 .376
BBS trained leg EC 2, 15 2.41 3.06 .129 .231
BBS untrained leg EC 2, 15 3.45 2.43 .060 .301
YBT trained leg 2, 16 1.49 3.80 .225 .157
YBT untrained leg 2, 16 4.40 2.51 .030 .355

Average Stability Measurements on BBS (Mean ± SD)a

Variable Trained Non-surgical Limb (EO/EC) Untrained Surgical Limb (EO/EC)


Training Control Training Control
Intervention
  Before 9.3 ± 3.7/12.4 ± 3.5 8.2 ± 3.0/10.7 ± 4.7 9.0 ± 2.9/12.3 ± 3.1 7.5 ± 2.3/10.6 ± 4.0
  During 6.8 ± 1.4/10.7 ± 3.4 6.8 ± 2.1/10.6 ± 3.5 7.0 ± 3.3/10.5 ± 3.2 8.5 ± 1.5/11.3 ± 2.7
  After 5.0 ± 1.8/8.9 ± 3.0 7.8 ± 2.6/10.4 ± 2.8 5.0 ± 1.54/9.4 ± 4.8 7.1 ± 1.5/11.2 ± 2.4
Cohen's db
   dt1–t2 1.62/0.91 0.89/0.00 1.12/1.00 −0.23/0.38
   dt2–t3 1.39/0.98 −0.64/0.11 1.28/0.57 1.05/0.09
   dt1–t3 2.63/1.91 0.26/0.13 2.68/1.47 0.27/−0.31

Average Dynamic Postural Control Measurements on YBT (Mean ± SD)a

Variable Trained Non-surgical Limb Untrained Surgical Limb


Training Control Training Control
Intervention
  Before 91.4 ± 4.9 87.4 ± 9.0 87.1 ± 6.8 85.8 ± 6.0
  During 92.0 ± 4.6 86.2 ± 8.6 87.5 ± 7.4 85.2 ± 7.2
  After 95.2 ± 4.8 88.2 ± 9.2 91.2 ± 6.1 85.8 ± 6.7
Cohen's db
   dt1–t2 −0.13 0.41 −0.41 0.24
   dt2–t3 −1.45 −0.69 −1.42 −0.25
   dt1–t3 −1.73 −0.28 −1.59 0.00
Authors

From the Departments of Health and Human Performance (LJH, JLC) and Psychology (DKF), Middle Tennessee State University, Murfreesboro, Tennessee; the Department of Health and Human Performance, University of Houston, Houston, Texas (LJH); the Department of Kinesiology, University of Connecticut, Storrs, Connecticut (LKL); and UCONN Health, Department of Orthopaedic Surgery, Farmington, Connecticut (LKL).

The authors have no financial or proprietary interest in the materials presented herein.

Correspondence: Layci J. Harrison, PhD, LAT, ATC, 3875 Holman St., Room 104, Garrison, Houston, TX 77204-6015. E-mail: Lharris5@central.uh.edu

Received: April 23, 2018
Accepted: September 07, 2018
Posted Online: January 29, 2019

10.3928/19425864-20181107-01

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