Two- and 3-dimensional knee valgus are reduced after an exercise intervention in young adults with demonstrable valgus during squatting.

CONTEXT: Two-dimensional (or medial knee displacement [MKD]) and 3-dimensional (3D) knee valgus are theorized to contribute to anterior cruciate ligament injuries. However, whether these displacements can be improved in the double-legged squat (DLS) after an exercise intervention is unclear. OBJECTIVE: To determine if MKD and 3D knee valgus are improved in a DLS after an exercise intervention. DESIGN: Randomized controlled clinical trial. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 32 participants were enrolled in this study and were randomly assigned to the control (n = 16) or intervention (n = 16) group. During a DLS, all participants demonstrated knee valgus that was corrected with a heel lift. INTERVENTION(S): The intervention group completed 10 sessions of directed exercise that focused on hip and ankle strength and flexibility over a 2- to 3-week period. MAIN OUTCOME MEASURE(S): We assessed MKD and 3D knee valgus during the DLS using an electromagnetic tracking system. Hip strength and ankle-dorsiflexion range of motion were measured. Change scores were calculated for MKD and 3D valgus at 0%, 10%, 20%, 30%, 40%, and 50% phases, and group (2 levels)-by phase (6 levels) repeated-measures analyses of variance were conducted. Independent t tests were used to compare change scores in other variables (α < .05). RESULTS: The MKD decreased from 20% to 50% of the DLS (P = .02) and 3D knee valgus improved from 30% to 50% of the squat phase (P = .001). Ankle-dorsiflexion range of motion (knee extended) increased in the intervention group (P = .009). No other significant findings were observed (P > .05). CONCLUSIONS: The intervention reduced MKD and 3D knee valgus during a DLS. The intervention also increased ankle range of motion. Our inclusion criteria might have limited our ability to observe changes in hip strength.

Comparison of integrated and isolated training on performance measures and neuromuscular control.

Traditional weight training programs use an exercise prescription strategy that emphasizes improving muscle strength through resistance exercises. Other factors, such as stability, endurance, movement quality, power, flexibility, speed, and agility are also essential elements to improving overall functional performance. Therefore, exercises that incorporate these additional elements may be beneficial additions to traditional resistance training programs. The purpose of the study was to compare the effects of an isolated resistance training program (ISO) and an integrated training program (INT) on movement quality, vertical jump height, agility, muscle strength and endurance, and flexibility. The ISO program consisted of primarily upper and lower extremity progressive resistance exercises. The INT program involved progressive resistance exercises, and core stability, power, and agility exercises. Thirty subjects were cluster randomized to either the ISO (n = 15) or INT (n = 15) training program. Each training group performed their respective programs 2 times per week for 8 weeks. The subjects were assessed before (pretest) and after (posttest) the intervention period using the following assessments: a jump-landing task graded using the Landing Error Scoring System (LESS), vertical jump height, T-test time, push-up and sit-up performance, and the sit-and-reach test. The INT group performed better on the LESS test (pretest: 3.90 ± 1.02, posttest: 3.03 ± 1.02; p = 0.02), faster on the T-test (pretest: 10.35 ± 1.20 seconds, posttest: 9.58 ± 1.02 seconds; p = 0.01), and completed more sit-ups (pretest: 40.20 ± 15.01, posttest: 46.73 ± 14.03; p = 0.045) and push-ups (pretest: 40.67 ± 13.85, posttest: 48.93 ± 15.17; p = 0.05) at posttest compared with pretest, and compared with the ISO group at posttest. Both groups performed more push-ups (p = 0.002), jumped higher (p < 0.001), and reached further (p = 0.008) at posttest compared with that at pretest. Performance enhancement programs should use an integrated approach to exercise selection to optimize performance and movement technique benefits.

Neuromuscular characteristics of individuals displaying excessive medial knee displacement.

CONTEXT: Knee-valgus motion is a potential risk factor for certain lower extremity injuries, including anterior cruciate ligament injury and patellofemoral pain. Identifying neuromuscular characteristics associated with knee-valgus motion, such as hip and lower leg muscle activation, may improve our ability to prevent lower extremity injuries. OBJECTIVE: We hypothesized that hip and lower leg muscle-activation amplitude would differ among individuals displaying knee valgus (medial knee displacement) during a double-legged squat compared with those who did not display knee valgus. We further suggested that the use of a heel lift would alter lower leg muscle activation and frontal-plane knee motion in those demonstrating medial knee displacement. DESIGN: Descriptive laboratory study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 37 healthy participants were assigned to the control (n = 19) or medial-knee-displacement (n = 18) group based on their double-legged squat performance. MAIN OUTCOME MEASURE(S): Muscle-activation amplitude for the gluteus maximus, gluteus medius, adductor magnus, medial and lateral gastrocnemius, and tibialis anterior was measured during 2 double-legged squat tasks. The first task consisted of performing a double-legged squat without a heel lift; the second consisted of performing a double-legged squat task with a 2-in (5.08-cm) lift under the heels. RESULTS: Muscle-activation amplitude for the hip adductor, gastrocnemius, and tibialis anterior was greater in those who displayed knee valgus than in those who did not (P < .05). Also, use of heel lifts resulted in decreased activation of the gluteus maximus, hip adductor, gastrocnemius, and tibialis anterior muscles (P < .05). Use of heel lifts also eliminated medially directed frontal-plane knee motion in those displaying medial knee displacement. CONCLUSIONS: Medial knee displacement during squatting tasks appears to be associated with increased hip-adductor activation and increased co-activation of the gastrocnemius and tibialis anterior muscles.

Systematic review of the balance error scoring system.

CONTEXT: The Balance Error Scoring System (BESS) is commonly used by researchers and clinicians to evaluate balance.A growing number of studies are using the BESS as an outcome measure beyond the scope of its original purpose. OBJECTIVE: To provide an objective systematic review of the reliability and validity of the BESS. DATA SOURCES: PubMed and CINHAL were searched using Balance Error Scoring System from January 1999 through December 2010. STUDY SELECTION: Selection was based on establishment of the reliability and validity of the BESS. Research articles were selected if they established reliability or validity (criterion related or construct) of the BESS, were written in English, and used the BESS as an outcome measure. Abstracts were not considered. RESULTS: Reliability of the total BESS score and individual stances ranged from poor to moderate to good, depending on the type of reliability assessed. The BESS has criterion-related validity with force plate measures; more difficult stances have higher agreement than do easier ones. The BESS is valid to detect balance deficits where large differences exist (concussion or fatigue). It may not be valid when differences are more subtle. CONCLUSIONS: Overall, the BESS has moderate to good reliability to assess static balance. Low levels of reliability have been reported by some authors. The BESS correlates with other measures of balance using testing devices. The BESS can detect balance deficits in participants with concussion and fatigue. BESS scores increase with age and with ankle instability and external ankle bracing. BESS scores improve after training.

Evidence supporting balance training in healthy individuals: a systemic review.

Balance is considered a risk factor for several injuries and consequently a focus of many strengthening, injury prevention, and rehabilitation programs. There are several studies that have evaluated the ability of balance training to improve balance ability in a healthy population with no general consensus. We conducted a systematic review to evaluate the body of evidence regarding the effectiveness of balance training on improving various forms of balance ability in a healthy population. Three electronic databases and the reference lists of selected articles were searched. Studies were included that evaluated balance ability before and after healthy subjects performed a multisession balance training program. Two individuals reviewed all articles and agreed upon the selection criteria. Sixteen articles were selected, abstracted, and reviewed. Means and measures of variability were recorded to calculate effect sizes, and study quality was assessed using the PEDro instrument. There is strong evidence to suggest that balance training can improve static balance ability on stable and unstable surfaces, as well as dynamic balance ability. Elite athletes have the potential to improve static balance on an unstable surface and dynamic balance ability, but a ceiling effect appears to occur with stable balance ability on a stable surface. Balance training programs performed at least 10 minutes per day, 3 days per week, for 4 weeks that incorporate various methods of balance training appear to improve balance ability. Types of balance training included the use of tilt boards, unstable surfaces, and dynamic body movements while maintaining a static stance.