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Noyes FR, Barber-Westin SD, Tutalo Smith S, Campbell T:A Training Program to Improve Neuromuscular Indices in Female High School Volleyball Players. In press, J Strength Conditioning Research
Abstract
The purpose of this study was to determine if a sports-specific training program could improve neuromuscular indices in female high school volleyball players. We combined components from a previously published knee ligament injury prevention intervention program for jump and strength training with additional exercises and drills to improve speed, agility, overall strength, and aerobic conditioning. We hypothesized that this sports-specific training program would lead to significant improvements in neuromuscular indices in high school female volleyball players. Thirty-four athletes (age 14.5 years + 1.0) participated in the supervised 6-week program, 3 days a week for approximately 90-120 minutes per session. The program was done on the school’s volleyball court and weight room facilities. The athletes underwent a video drop-jump test, multi-stage fitness test, vertical jump test, and sit-up test before and after training. A significant increase was found in the mean VO2max score (p < 0.001), as 73% of the athletes improved this score. A significant improvement was found in the sit-up test (p = 0.03) and in the vertical jump test (p = 0.05), as 68% of the athletes increased their scores. In the drop-jump video test, significant increases were found in both the mean absolute knee separation distance (p = 0.002) and in the mean normalized knee separation distance (p = 0.04), indicating improved lower limb alignment on landing. No athlete sustained an injury or developed an overuse syndrome during training. This program significantly improved lower limb alignment on a drop-jump test, abdominal strength, estimated maximal aerobic power, and vertical jump height and may be implemented in high school female volleyball programs.
Barber-Westin SD, Hermeto A, Noyes FR: A Six-Week Neuromuscular Training Program for Competitive Junior Tennis Players. J Strength Conditioning Research 24: 2372-2382, 2010.
Abstract
This study evaluated the effectiveness of a tennis-specific training program on improving neuromuscular indices in competitive junior players. Tennis is a demanding sport as it requires speed, agility, explosive power, and aerobic conditioning along with the ability to react and anticipate quickly and there are limited studies that evaluate these indices in young players following a multi-week training program. The program designed for this study implemented the essential components of a previously published neuromuscular training program and also included exercises designed to improve dynamic balance, agility, speed, and strength. Fifteen junior tennis players (10 girls, 5 boys; mean age, 13.0 + 1.5 years) who routinely participated in local tournaments and high school teams participated in the 6-week supervised program. Training was conducted 3 times a week, with sessions lasting 1.5 hours that included a dynamic warm-up, plyometric and jump training, strength training (lower extremity, upper extremity, core), tennis-specific drills, and flexibility. After training, statistically significant improvements and large to moderate effect sizes were found in the single-leg triple crossover hop for both legs (p < .05), the baseline forehand (p = .006) and backhand (p = .0008) tests, the service line (p = .0009) test, the 1-court suicide (p < .0001), the 2-court suicide (p = .02), and the abdominal endurance test (p = .01). Mean improvements between pre-train and post-train test sessions were 15% for the single-leg triple crossover hop, 10-11% for the baseline tests, 18% for the service line test, 21% for the 1-court suicide, 10% for the 2-court suicide, and 76% for the abdominal endurance test. No athlete sustained an injury or developed an overuse syndrome as a result of the training program. The results demonstrate that this program is feasible, low in cost, and appears to be effective in improving the majority of neuromuscular indices tested. We accomplished our goal of developing training and testing procedures that could all be performed on the tennis court.
Barber-Westin SD, Tutalo Smith S, Campbell T, Noyes FR: The Drop-Jump Video Screening Test: Retention of Improvement in Neuromuscular Control in Female Volleyball Players. In press, J Strength Conditioning Research, 2010.
Abstract
A valgus lower limb alignment is commonly documented during noncontact ACL injuries. We previously developed a videographic drop-jump test to measure overall lower limb alignment in the coronal plane as a screening tool to detect an such an abnormal (valgus) position on landing. A neuromuscular retraining program developed for female athletes was shown to be effective in improving lower limb alignment on this test immediately following completion of training. What remained unknown was whether these improvements would be retained for longer periods of time. Therefore, this study was undertaken to determine if these improvements in overall lower limb alignment would be retained up to one year after training. Sixteen competitive, experienced female high school volleyball players underwent the video drop-jump test and then completed the neuromuscular retraining program. The program consisted of a dynamic warm-up, jump training, speed and agility drills, strength training, and static stretching and was performed 3 times a week for 6 weeks. The athletes repeated the drop-jump test immediately upon completion of training, and then 3- and 12-months later. Significant improvements were found in the mean normalized knee separation distance between the pre- and post-trained values for all test sessions (p < 0.01). Immediately after training, 11 athletes (69%) displayed significant improvements in the mean normalized knee separation distance which were retained 12 months later. Five athletes failed to improve. The video drop-jump test, while not a risk indicator for a knee ligament injury, provides a cost-effective general assessment of lower limb position and depicts athletes who have poor control on landing and acceleration into a vertical jump.
Dempsey AR et al: Changing Sidestep Cutting Technique Reduces Knee Valgus Loading. Am J Sports Med 37: 2194-2200, 2009.
Abstract:
Background Common lower limb postures have been found when noncontact anterior cruciate ligament (ACL) injuries occur during sidestep cutting tasks. These same postures have been linked to knee loadings known to stress the ACL.
Hypothesis Whole body technique modification would reduce knee loading.
Study Design Controlled laboratory study.
Methods Experienced team sport athletes were recruited for whole body sidestep cutting technique modification. Before and after a 6-week technique modification training, participants performed sidestep cutting tasks while ground-reaction force and motion data were collected. A kinematic and inverse dynamics model was used to calculate 3-dimensional knee loading during sidestep cutting.
Results At initial foot contact, the participants placed their stance foot closer to the body’s midline and held their torso more upright, in line with the aims of the technique modification training. This was accompanied by significantly lower peak valgus moments in the weight acceptance phase of stance. Both postural changes were correlated with the change in peak valgus moment.
Conclusion Whole body sidestep cutting technique modification resulted in reduced knee loading.
Clinical Relevance Implementation of whole body technique modification may produce effective ACL injury prevention programs in sports involving sidestep cutting.
Brophy RH, Gill CS, Lyman S, Barnes RP, Rodeo SA, Warren RF: Effect of anterior cruciate ligament reconstruction and meniscectomy on length of career in National Football League athletes: a case control study. Am J Sports Med 37: 2102-7, 2009.
Abstract
BACKGROUND: Meniscal and anterior cruciate ligament (ACL) injuries are common in college football athletes. The effect of meniscectomy and/or ACL surgery on the length of an athlete’s career in the National Football League (NFL) has not been well examined.
HYPOTHESIS: Athletes with a history of meniscectomy or ACL surgery before the NFL combine have a shorter career than matched controls.
STUDY DESIGN: Case-control study; Level of evidence, 3.
METHODS: A database containing the injury history and career NFL statistics of athletes from 1987-2000 was used to match athletes with a history of meniscectomy and/or ACL surgery, and no other surgery or major injury, to controls without previous surgeries. Athletes were matched by position, year drafted, round drafted, and additional injury history.
RESULTS: Fifty-four athletes with a history of meniscectomy, 29 with a history of ACL reconstruction, and 11 with a history of both were identified and matched with controls. Isolated meniscectomy reduced the length of career in years (5.6 vs 7.0; P = .03) and games played (62 vs 85; P = .02). Isolated ACL surgery did not significantly reduce the length of career in years or games played. Comparing the athletes with meniscectomy or ACL reconstruction to athletes with combined ACL reconstruction and meniscectomy, a history of both surgeries, resulted in a shorter career in games started (7.9 vs 35.1; P <.01), games played (41 vs 63; P = .07), and years (4.0 vs 5.8; P = .08) than a history of either surgery alone.
CONCLUSION: A history of meniscectomy, but not ACL reconstruction, shortens the expected career of a professional football player. A combination of ACL reconstruction and meniscectomy may be more detrimental to an athlete’s durability than either surgery alone. Further research is warranted to better understand how these injuries and surgeries affect an athlete’s career and what can be done to improve the long-term outcome after treatment.
Schultz SJ, Schmitz RJ: Effects of Transverse and Frontal Plane Knee Laxity on Hip and Knee Neuromechanics During Drop Landings. Am J Sports Med 37: 1821-1830, 2009.
Background: Varus-valgus (LAXVV) and internal-external (LAXIER) rotational knee laxity have received attention as potential contributing factors in anterior cruciate ligament injury. This study compared persons with above- and below-average LAXVV and LAXIER values on hip and knee neuromechanics during drop jump landings.
Hypothesis: People with greater LAXVV and LAXIER values will have greater challenges controlling frontal and transverse plane knee motions, as evidenced by greater joint excursions, joint moments, and muscle activation levels during the landing phase.
Study Design: Descriptive laboratory study.
Methods: Recreationally active participants (52 women and 44 men) between 18 and 30 years old were measured for LAXVV and LAXIER and for their muscle activation and transverse and frontal plane hip and knee kinetics and kinematics during the initiallanding phase of a drop jump. The mean value was obtained for each sex, and those with above-average values on LAXVV and LAXIER (LAXHIGH = 17 women, 16 men) were compared with those with below-average values (LAXLOW = 18 women, 17 men).
Results: Women with LAXHIGH verus LAXLOW were initially positioned in greater hip adduction and knee valgus and also produced more prolonged internal hip adduction and knee varus moments as they moved toward greater hip adduction and internal rotation as the landing progressed. These patterns in LAXHIGH women were accompanied by greater prelanding and postlanding muscle activation amplitudes. Men with LAXHIGH versus LAXLOW also demonstrated greater hip adduction motion and produced greater internal hip internal rotation and knee varus and internal rotation moments.
Conclusion: Participants with greater LAXVV and LAXIER landed with greater hip and knee transverse and frontal plane hip and knee motions.
Clinical Relevance: People (especially, women) with increased frontal and transverse plane knee laxity demonstrate motions associated with noncontact anterior cruciate ligament injury mechanisms.
Zebis MK et al:Identification of athletes at future risk of anterior cruciate ligament ruptures by neuromuscular screening. Am J Sports Med 37: 1967-1973, 2009.
BACKGROUND: A high percentage of female athletes who sustain an anterior cruciate ligament (ACL) rupture suffer serious long-term consequences such as osteoarthritis and disability. Thus, identification of risk factors has high clinical relevance in the prevention of ACL rupture. Hypothesis Noninjured athletes with low knee flexor electromyography (EMG) preactivity and high knee extensor EMG preactivity during sidecutting are at increased risk of future ACL rupture.
STUDY DESIGN: Cohort study (prognosis); Level of evidence, 2.
METHODS: Fifty-five elite female athletes (team handball and soccer) aged 24 +/- 5 years with no history of ACL injury were tested for EMG preactivity of vastus lateralis and medialis, rectus femoris, semitendinosus, and biceps femoris during a standardized side-cutting maneuver. The incidence of ACL ruptures was registered in the following 2 match seasons.
RESULTS: During the subsequent 2 match seasons, 5 athletes sustained a confirmed noncontact ACL rupture. Before injury, all 5 players displayed a neuromuscular pattern that differed from the noninjured players, characterized by reduced EMG preactivity for the semitendinosus (ST) and elevated EMG preactivity for the vastus lateralis (VL) (P < .01). On the basis of these findings, a high-risk zone was defined as one standard deviation above the mean VL-ST difference. In our population, 5 of 10 subjects with a VL-ST difference in this zone sustained an ACL injury during the study period.
CONCLUSION: In the present study, currently noninjured female athletes with reduced EMG preactivity of the ST and increased EMG preactivity of the VL during side cutting were at increased risk of future noncontact ACL rupture. Our data indicate that a high-risk zone can be used to identify noninjured players at high risk of future ACL rupture. Consequently, individual preventive efforts can be introduced in time. However, large prospective studies are needed to confirm this finding before definitive clinical recommendations can be made.
Barber-Westin SD, Noyes FR, Smith S, Campbell T: Reducing the risk of noncontact anterior cruciate ligament injuries in the female athlete. The Physician and Sports Medicine, 37:49-61, 2009.
High school and collegiate female athletes have a significantly increased risk of sustaining a noncontact anterior cruciate ligament injury compared with male athletes participating in the same sport. This review summarizes the current knowledge of the risk factors hypothesized to influence this problem, and the neuromuscular training programs designed to correct certain biomechanical problems noted in female athletes. The risk factors include a genetic predisposition for sustaining a knee ligament injury, environmental factors, anatomical indices, hormonal influences, and neuromuscular factors. The greatest amount of research in this area has studied differences between female and male athletes in movement patterns during athletic tasks; muscle strength, activation, and recruitment patterns; and knee joint stiffness under controlled, preplanned, and reactive conditions in the laboratory. Neuromuscular retraining programs have been developed in an attempt to reduce these differences. The successful programs teach athletes to control the upper body, trunk, and lower body position; lower the center of gravity by increasing hip and knee flexion during activities; and develop muscular strength and techniques to land with decreased ground reaction forces. In addition, athletes are taught to preposition the body and lower extremity prior to initial ground contact to obtain the position of greatest knee joint stability and stiffness. Two published programs have significantly reduced the incidence of noncontact anterior cruciate ligament injuries in female athletes participating in basketball, soccer, and volleyball. Other programs were ineffective, had a poor study design, or had an insufficient number of participants, which precluded a true reduction in the risk of this injury. In order to determine which risk factors for noncontact anterior cruciate ligament ruptures are significant, future investigations should include larger cohorts of athletes in multiple sports, analyze factors from all of the major risk categories, and follow athletes for at least one full athletic season. Future risk assessment studies should incorporate reactive tasks under more realistic sports conditions.
Herman DC et al:The effects of feedback with and without strength training on lower extremity biomechanics.. Am J Sports Med 37: 1301-1308, 2009.
BACKGROUND: Feedback instruction is a proven modality for the alteration of motion patterns. There are no existing data on the contribution of strength training, when combined with feedback instruction, to the altering of lower extremity biomechanics.
HYPOTHESIS: Lower extremity muscle strength training provides an increased capacity to alter knee and hip biomechanics during a stop-jump task in response to a feedback protocol.
STUDY DESIGN: Controlled laboratory study.
METHODS: Knee and hip 3-dimensional kinematic and kinetic data were collected for 58 female recreational athletes while performing 3 stop-jump tasks after completing a 9-week strength training program (ST-FB; n = 29) or a 9-week period of no strength training (FB; n = 29). Data were then collected for both groups after completing a jump-landing feedback instruction protocol. Knee and hip joint angles, as well as resultant forces and moments, were calculated.
RESULTS: Across all participants, there were decreased peak vertical ground-reaction forces (P < .001) and increased knee flexion (P = .050), hip flexion (P < .001), and hip abduction (P = .032) angles, subsequent to the feedback protocol. Hip abduction angle (P < .001) increased in the ST-FB group but not the FB group, and peak knee anterior shear force (P = .015) decreased in the ST-FB group but increased in the FB group (P = .009).
CONCLUSION: The results indicate that strength training, when used in conjunction with video-assisted feedback, may provide an increased capacity for the alteration of knee and hip biomechanics.
CLINICAL RELEVANCE: Programs that include both strength training and movement education through feedback may be necessary to increase the effectiveness of anterior cruciate ligament prevention programs. Strength training may provide an increased capacity for athletes to respond to other intervention modalities used in anterior cruciate ligament injury prevention programs.
Padua DA, DiStefano LJ: Sagittal Plane Knee Biomechanics and Vertical Ground Reaction Forces are Modified Following ACL Injury Prevention Programs: A Systematic Review. Spts Health 1: 165-173, 2009.
Context: Injuries to the anterior cruciate ligament (ACL) occur because of excessive loading on the knee. ACL injury prevention programs can influence sagittal plane ACL loading factors and vertical ground reaction force (VGRF).
Objective: To determine the influence of ACL injury prevention programs on sagittal plane knee biomechanics (anterior tibial shear force, knee flexion angle/moments) and VGRF.
Data Sources: The PubMed database was searched for studies published between January 1988 and June 2008. Reference lists of selected articles were also reviewed.
Study Selection: Studies were included that evaluated healthy participants for knee flexion angle, sagittal plane knee kinetics, or VGRF after performing a multisession training program. Two individuals reviewed all articles and determined which articles met the selection criteria. Approximately 4% of the articles fulfilled the selection criteria.
Data Extraction: Data were extracted regarding each program’s duration, frequency, exercise type, population, supervision, and testing procedures. Means and variability measures were recorded to calculate effect sizes. One reviewer extracted all data and assessed study quality using PEDro (Physiotherapy Evidence Database). A second reviewer (blinded) verified all information.
Results: There is moderate evidence to indicate that knee flexion angle, external knee flexion moment, and VGRF can be successfully modified by an ACL injury prevention program. Programs utilizing multiple exercises (ie, integrated training) appear to produce the most improvement, in comparison to that of single-exercise programs. Knee flexion angle was improved following integrated training (combined balance and strength exercises or combined plyometric and strength exercises). Similarly, external knee flexion moment was improved following integrated training consisting of balance, plyometric, and strength exercises. VGRF was improved when incorporating supervision with instruction and feedback on proper technique.
Conclusion: ACL injury prevention programs that are aimed at modifying sagittal plane knee biomechanics and VGRF should use an integrated training approach that incorporates instruction and feedback on proper movement technique.
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