Prior to training, both the experimental and the control groups of female athletes demonstrated similar performance on the SEBT in all measured variables. Following a NMTP, the SEBT composite score significantly improved in the training group compared to the control group, who did not participate in a NMTP. Improvement in the SEBT composite score in the NMTP group appeared to be dependent on an improvement in the posterolateral and posteromedial reach, as indicated by the independent reach analysis. No differences in reach were found in the anterior direction. Improvements in the posterolateral and posteromedial direction are likely the result of improved neuromuscular control and dynamic balance, and less related to lower extremity strength, as was suggested by Thorpe and Ebersole.32
The NMTP design was based on injury prevention research.9,10,11,15,17–19,21,24,32
Each aspect of the NMTP was enhanced with verbal feedback and visual demonstration to improve the athletes biomechanical technique.9,31
Current literature supports the use of NMTP that incorporate core stability as part of treatment programs to prevent injury of the ankle or knee.16,34
Decreased neuromuscular control of the trunk appears to influence dynamic stability of the lower extremity during high-speed athletic maneuvers.34
In a systematic review by Thacker et al,31
6 prospective studies that addressed training programs that all proved to have reduced knee injuries were chosen. The 6 programs consisted of neuromuscular, proprioception, and/or acceleration training. Of the 6 studies, 4 were randomized controlled studies, but none reported blinding of the assessor or the details of the randomization of the subjects. The training programs demonstrated positive results, with significantly reduced knee injury rates compared to controls who did not participate in a training program.31
Other studies have also confirmed improved postural control and balance following rehabilitation and training programs in individuals with chronic ankle instability.5,16
The individuals in the NMTP in the current study showed improvements in the SEBT composite scores when compared to nontrained controls. However, its effect on knee or ankle injury rate was not assessed in this study. The SEBT may have the potential to be a corollary outcome measure that can be utilized to compare the efficacy of programs that reduce injury rates.27
Prior research indicates that isolated strength measures may not have an effect on the SEBT score. Thorpe and Ebersole32
compared recreational and collegiate female soccer student athletes and found no difference in isokinetic strength. They also showed that there was a low to moderate correlation between SEBT performances and lower extremity strength. Therefore, other factors, such as muscle activation and proprioception, may have a stronger relative relationship to the SEBT performance than non–weight-bearing strength testing. In addition, neither group of the above study participated in a NMTP that might have contributed to the lack of change on the SEBT.
Robinson and Gribble29
suggested that improvements in the SEBT were not due to strength or core stability but, rather, to increased knee and hip flexion on the stance limb. Their study consisted of 20 participants from a university setting who did not undergo any intervention program. Stepwise regression revealed that hip flexion and knee flexion, separately and in combination, accounted for 62% to 95% of the variance in reach distances.29
It is important to consider that Robinson and Gribble29
did not measure lower extremity strength. It is possible that participants who showed increased knee and hip flexion potentially had more lower extremity strength compared to the subjects who had less knee and hip flexion angles.
Sato and Mokha30
looked at the effects of a core strength training program on ground reaction forces, stability of the lower extremity using the SEBT, and overall running performance in recreational and competitive runners. They did not find any improvements in SEBT after implementing a 6-week core strength training program. However, there are several differences that existed between this study and the current one. These included a lack of balance training and biomechanical feedback, a different definition of core stability training, and a different testing protocol for the SEBT.
Specific thresholds have been developed to screen for injury risk using the SEBT. Plisky et al26,27
found that female athletes with less than 94% composite reach during the SEBT were upwards of 6 times more likely to experience an injury. Although the mean SEBT composite score for both groups was initially above the 94% threshold for injury risk, the NMTP focused on lower extremity strength and core stability training did improve the SEBT composite score. Individually, in the trained group, 7/18 of the limbs scored below the 94% threshold at pretraining. Posttraining, only 2/18 limbs were below 94% threshold. The 2 subjects who remained below the threshold posttraining were below 94% pretraining. Based on Myer et al,19
the results are expected to be magnified in athletes who would fall below the injury risk threshold. This infers that participation in a NMTP that focuses on lower extremity strength and core stability may reduce the risk of injury. If a NMTP could improve SEBT measures, then athletes could be evaluated for SEBT composite reach before competition and be preventatively placed in a NMTP targeted toward deficits in lower extremity strength and core stability.
The SEBT may be a sufficiently sensitive tool for trained athletes that can be used prior to competition to assess neuromuscular factors more comprehensively than strength alone.32
The SEBT has also been examined to determine the correlation between anterior cruciate ligament injury with the lack of postural control and was found to successfully demonstrate limitations in individuals who were anterior cruciate ligament deficient compared with asymptomatic individuals. Individuals who were anterior cruciate ligament deficient had significantly lower reach scores on both the involved and uninvolved extremity compared to uninjured controls.6
Following the NMTP, there was no difference in composite score between limbs in the control group or in the experimental group. This may be due to the design of the NMTP, which focused on the performance of exercises equally on each limb and likely contributed to the lack of a limb effect. Establishing limb symmetry was important because limb dominance and side-to-side imbalance in lower extremity measures have been found to be a risk factor for anterior cruciate ligament injury.3,9
The SEBT has successfully been used to demonstrate asymmetrical impairments in functional balance on the involved side in individuals with chronic ankle instability or anterior cruciate ligament deficiency compared to uninjured controls.4,6,7,23
Training and rehabilitation programs have also been reported to reduce the side-to-side asymmetry in functional balance.5,6,16
Study limitations should be taken into consideration. Four subjects were excluded from the experimental group, resulting in a 31% drop-out rate. Although it was a higher drop-out rate, the power analysis confirmed that the sample size was sufficient. Another limitation is the small number of adolescent female soccer players, which decreases the applicability to other populations. Finally, training was performed without the benefits of random assignment and without the blinding of the investigators.
Further investigation is necessary to determine if a NMTP that improves the SEBT composite score would reduce in-season injury rates. A randomized controlled trial with longitudinal injury tracking is needed to assess cause and effect to determine if the NMTP does indeed have an effect on in-season injury rates. A longitudinal study is necessary to determine if the NMTP has lasting effects on the subject’s strength and core stability.
Other implications for future research include utilizing the SEBT for assessment and screening tools for athletes. The SEBT is an easy and practical tool that may be used as a preseason screening tool to determine which athletes may be more at risk for a lower extremity injury. It may also be important to combine the SEBT with other screening tools to better determine which athletes may be in greater jeopardy of injury.