Retention Drop-Jump Test Study Results

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. J Strength Conditioning Research 24: 3055-3062, 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.

 

Jump-land characteristics and muscle strength development in young athletes

Barber-Westin SD, Noyes FR, Galloway MG: Jump-land characteristics and muscle strength development in young athletes: A gender comparison of 1140 athletes 9 to 17 years of age. Am J Sports Med 34: 375-384, 2006.

From the Cincinnati Sportsmedicine

Research and Education Foundation

“Reprinted with permission of the American Journal of Sports Medicine. Further reproduction is prohibited.”

Background: Many authors have speculated that altered neuromuscular control and strength of the lower extremity are responsible for the gender disparity in knee ligament injury rates. Hypotheses: Significant increases in normalized quadriceps and hamstrings strength and limb symmetry on single-legged hop tests occur with age. No gender differences in strength occur until age 14 years, after which boys generate greater peak torques than do girls. Age and gender do not influence lower limb alignment on a drop-jump test.

Study Design: Cross-sectional study.

Methods: We studied the effect of age and gender in 1140 athletes, 9 to 17 years old, on muscle strength and neuromuscular control during functional activities. Isokinetic quadriceps and hamstrings strength was measured at 300 deg/sec. Limb symmetry was assessed with single-legged hop tests. A video drop-jump test determined lower limb alignment in the coronal plane.

Results: Extension peak torques significantly increased with age; maximum strength was noted in girls at age 13 years and in boys at age 14 years (p < 0.001). Although maximum flexion strength occurred in boys at age 14 years (p < 0.001), girls had only slight increases from ages 9 to 11 years (p = NS). Boys aged 14 to 17 years had significantly greater normalized isokinetic strength than did age-matched girls. No age or gender effects existed in limb alignment on the drop-jump test or limb symmetry on single-legged hop testing.

Conclusions: Maximum hamstrings strength was noted in female athletes by age 11, compared to age 14 in male athletes, and a distinct lower limb valgus alignment existed in the majority of all athletes on landing. The absence of a gender difference in lower limb alignment on landing suggests other factors may be responsible for the gender disparity in knee ligament injury rates.

 

The effect of neuromuscular training on the incidence of knee injury in female athletes

Deaconess Hospital, Cincinnati, Ohio

Hewett TE, Lindenfeld TN, Riccobene JV, and Noyes FR: The effect of neuromuscular training on the incidence of knee injury in female athletes. A prospective study. Am. J. Sports Med. 27: 699-706, 1999.

“Reprinted with permission of the American Journal of Sports Medicine. Further reproduction is prohibited.”

Objective

To prospectively evaluate the effect of neuromuscular training on the incidence of knee injury in female athletes, we monitored two groups of female athletes, one trained before sports participation and the other not trained, and a group of untrained male athletes throughout the high school soccer, volleyball, and basketball seasons.

Results

There were 14 serious knee injuries in the 1263 athletes tracked through the study. Ten of 463 untrained female athletes sustained serious knee injuries (8 noncontact), 2 of 366 trained female athletes sustained serious knee injuries (0 noncontact), and 2 of 434 male athletes sustained serious knee injuries (1 noncontact). The knee injury incidence per 1000 athlete-exposures was 0.43 in untrained female athletes, 0.12 in trained female athletes, and 0.09 in male athletes (P = 0.02, chi-square analysis). Untrained female athletes had a 3.6 times higher incidence of knee injury than trained female athletes (P = 0.05) and 4.8 times higher than male athletes (P = 0.03). The incidence of knee injury in trained female athletes was not significantly different from that in untrained male athletes (P = 0.86). The difference in the incidence of noncontact injuries between the female groups was also significant (P = 0.01).

Conclusion

This prospective study demonstrated a decreased incidence of knee injury in female athletes after a specific plyometric training program.

 

Plyometric training in female athletes. Decreased impact forces and increased hamstring torques

Hewett TE, Stroupe AL, Nance TA, and Noyes FR: Plyometric training in female athletes. Decreased impact forces and increased hamstring torques. Am J Sports Med 24: 765-773, 1996.

From the Cincinnati Sportsmedicine Research and Education Foundation and Deaconess Hospital, Cincinnati, Ohio
“Reprinted with permission of the American Journal of Sports Medicine. Further reproduction is prohibited.”

Objective

The purpose of this study was to test the effect of a jump-training program on landing mechanics and lower extremity strength in female athletes involved in jumping sports. These parameters were compared before and after training with those of male athletes. The program was designed to decrease landing forces by teaching neuromuscular control of the lower limb during landing and to increase vertical jump height.

Results

After training, peak landing forces from a volleyball block jump decreased 22%, and knee adduction and abduction moments (medially and laterally directed torques) decreased approximately 50%. Multiple regression analysis revealed that these moments were significant predictors of peak landing forces. Female athletes demonstrated lower landing forces than male athletes and lower adduction and abduction moments after training. External knee extension moments (hamstring muscle-dominant) of male athletes were threefold higher than those of female athletes. Hamstring-to-quadriceps muscle peak torque ratios increased 26% on the nondominant side and 13% on the dominant side,

correcting side-to-side imbalances. Hamstring muscle power increased 44% with training on the dominant side and 21% on the nondominant. Peak torque ratios of male athletes were significantly greater than those of untrained female athletes, but similar to those of trained females. Mean vertical jump height increased approximately 10%

Conclusion

This training may have a significant effect on knee stabilization and prevention of serious knee injury among female athletes.