Catherine Y. Wild

Musculoskeletal and estrogen changes during the adolescent growth spurt in girls

INTRODUCTION The adolescent growth spurt is associated with rapid growth and hormonal changes, thought to contribute to the increased anterior cruciate ligament injury risk in girls. However, relatively little is known about these musculoskeletal and estrogen changes during the growth spurt in girls. PURPOSE To investigate the longitudinal changes in estrogen as well as anterior knee laxity and lower limb strength and flexibility throughout the adolescent growth spurt in girls. METHODS Thirty-three healthy girls, age 10-13 yr, in Tanner stage II and 4-6 months from their peak height velocity were recruited. Participants were tested up to four times during the 12 months of their growth spurt, according to the timing of their maturity offset (test 1: maturity offset = -6 to -4 months; test 2: maturity offset = 0 months; test 3: maturity offset = +4 months; test 4: maturity offset = +8 months). During each testing session, anterior knee laxity, lower limb flexibility, and isokinetic strength as well as saliva measures of estradiol concentration were measured. RESULTS A significant (P = 0.002) effect of time on anterior knee laxity was found from the time of peak height velocity, although no changes in estradiol concentration were displayed over time (P = 0.811). Participants displayed a significant increase (P < 0.05) in isokinetic quadriceps strength over time, with no apparent increase in isokinetic hamstring strength. CONCLUSIONS We speculate that increased quadriceps strength, combined with increased knee laxity and no accompanying hamstring strength development during the adolescent growth spurt in girls, might contribute to a decrease in their knee joint stability during landing tasks. These musculoskeletal changes could potentially increase anterior cruciate ligament injury risk at a time of rapid height and lower limb growth.

Why Do Girls Sustain More Anterior Cruciate Ligament Injuries Than Boys

Sport is the leading cause of injury among adolescents and girls incur more non-contact anterior cruciate ligament (ACL) ruptures than boys, with this gender disparity in injury incidence apparent from the onset of puberty. Although the mechanisms for this gender disparity in ACL injuries are relatively unknown, hormonal, anatomical and biomechanical factors have been implicated. Puberty is associated with rapid skeletal growth and hormonal influx, both of which are thought to contribute to alterations in ACL metabolic and mechanical properties, as well as changes in lower limb strength and flexibility, ultimately influencing landing technique. Therefore, the aim of this review is to explain (i) the effects of changes in estrogen levels on the metabolic and mechanical properties of the ACL; (ii) changes in musculoskeletal structure and function that occur during puberty, including changes in knee laxity, and lower limb flexibility and strength; and (iii) how these hormonal and musculoskeletal changes impact upon the landing technique displayed by pubescent girls.Despite evidence confirming estrogen receptors on the ACL, there are still conflicting results as to how estrogen affects the mechanical properties of the ACL, particularly during puberty. However, during this time of rapid growth and hormonal influx, unlike their male counterparts, girls do not display an accelerated muscle strength spurt and the development of their hamstring muscle strength appears to lag behind that of their quadriceps. Throughout puberty, girls also display an increase in knee valgus when landing, which is not evident in boys. Therefore, it is plausible that this lack of a defined strength spurt, particularly of the hamstring muscles, combined with the hormonal effects of estrogen in girls, may contribute to a more ‘risky’ lower limb alignment during landing, in turn, contributing to a greater risk of ACL injury. There is, however, a paucity of longitudinal studies specifically examining the lower limb musculoskeletal structural and functional changes experienced by girls throughout puberty, as well as how these changes are related to estrogen fluctuations characteristic of puberty and their effects on landing biomechanics. Therefore, further research is recommended to provide greater insight as to why pubescent girls are at an increased risk of non-contact ACL injuries during sport compared with boys. Such information will allow the development of evidence-based training programmes aimed at teaching girls to land more safely and with greater control of their lower limbs in an attempt to reduce the incidence of ACL ruptures during puberty.

Insufficient Hamstring Strength Compromises Landing Technique in Adolescent Girls

PURPOSE Women sustain more anterior cruciate ligament (ACL) ruptures than men, and this gender disparity is apparent from pubertal onset. Although the hamstring muscles play a vital role in ACL protection during landing by restraining anterior tibial motion relative to the femur, it is unknown whether hamstring strength affects landing biomechanics during a functional movement. This study aimed to determine whether pubescent girls with lower hamstring strength displayed different lower limb biomechanics when landing from a leap compared with girls with higher hamstring strength. METHODS Thirty-three healthy girls, age 10-13 yr, in Tanner stage II (pubertal onset) and 4-6 months from their peak height velocity were recruited. The concentric and the eccentric isokinetic strength of the hamstring and quadriceps muscles were assessed. On the basis of peak concentric hamstrings torque, participants were divided into a lower (peak torque < 45 N·m) and higher (peak torque > 60 N·m) strength group. Participants performed a functional landing movement, during which ground reaction forces (1000 Hz), lower limb electromyography (1000 Hz), and kinematic data (100 Hz) were collected. RESULTS Girls with lower hamstring strength displayed significantly (P < 0.05) greater knee abduction alignment, reduced hip abduction moments, and greater ACL loading at the time of the peak anteroposterior ground reaction forces compared with their stronger counterparts. CONCLUSIONS Girls with reduced hamstring strength appear to have a decreased capacity to control lower limb frontal plane alignment. This reduced capacity appears to contribute to increased ACL loading and, in turn, increased potential for injury.

The Effect of the Mulligan Knee Taping Technique on Patellofemoral Pain and Lower Limb Biomechanics

Background: Patellofemoral pain (PFP) affects 25% of the general population, occurring 2 times more often in females compared with males. Taping is a valuable component of the management plan for altering lower limb biomechanics and providing pain relief; however, the effects of alternative taping techniques, such as Mulligan knee taping, appear yet to be researched. Purpose: To determine whether the Mulligan knee taping technique altered levels of perceived knee pain and lower limb biomechanics during a single-legged squat (SLSq) in adult females with PFP. Study Design: Controlled laboratory study. Methods: A total of 20 female patients with PFP, aged 18 to 35 years, participated in this study. Participants performed 3 to 5 SLSq on their most symptomatic limb during a taped (Mulligan knee taping technique) and nontaped (control) condition. During the eccentric phase of the SLSq, the 3-dimensional kinematics (250 Hz) of the knee and hip and the ground-reaction forces (1000 Hz) and muscle activation patterns (1000 Hz) of the gluteus medius, vastus lateralis, and vastus medialis oblique were measured. Participants’ perceived maximum knee pain was also recorded after the completion of each squat. Results: Between-condition differences were found for hip kinematics and gluteus medius activation but not for kinetics or vastus medialis oblique and vastus lateralis muscle activity (timing and activation). Compared with the nontaped condition, the Mulligan knee taping technique significantly (P = .001) reduced perceived pain during the SLSq (mean ± SD: 2.29 ± 1.79 and 1.29 ± 1.28, respectively). In the taped condition compared with the control, the onset timing of the gluteus medius occurred significantly earlier (120.6 ± 113.0 and 156.6 ± 91.6 ms, respectively; P = .023) and peak hip internal rotation was significantly reduced (6.38° ± 7.31° and 8.34° ± 7.92°, respectively; P = .002). Conclusion: The Mulligan knee taping technique successfully reduced knee pain in participants with PFP. This is the first study to establish a link between Mulligan knee taping and the reduction of PFP in conjunction with decreased hip internal rotation and earlier activation of gluteus medius. Clinical Relevance: The Mulligan knee taping technique may benefit the clinical environment by providing an alternative evidence-based treatment plan for PFP.

Effect of External Ankle Support on Ankle and Knee Biomechanics During the Cutting Maneuver in Basketball Players

Background: Despite the high prevalence of lower extremity injuries in female basketball players as well as a high proportion of athletes who wear ankle braces, there is a paucity of research pertaining to the effects of ankle bracing on ankle and knee biomechanics during basketball-specific tasks. Purpose: To compare the effects of a lace-up brace (ASO), a hinged brace (Active T2), and no ankle bracing (control) on ankle and knee joint kinematics and joint reaction forces in female basketball athletes during a cutting maneuver. Study Design: Controlled laboratory study. Methods: Twenty healthy, semi-elite female basketball players performed a cutting task under both ankle brace conditions (lace-up ankle brace and hinged ankle brace) and a no-brace condition. The 3-dimensional kinematics of the ankle and knee during the cutting maneuver were measured with an 18-camera motion analysis system (250 Hz), and ground-reaction force data were collected by use of a multichannel force plate (2000 Hz) to quantify ankle and knee joint reaction forces. Conditions were randomized using a block randomization method. Results: Compared with the control condition, the hinged ankle brace significantly restricted peak ankle inversion (mean difference, 1.7°; P = .023). No significant difference was found between the lace-up brace and the control condition (P = .865). Compared with the lace-up brace, the hinged brace significantly reduced ankle and knee joint compressive forces at the time of peak ankle dorsiflexion (mean difference, 1.5 N/kg [P = .018] and 1.4 N/kg [P = .013], respectively). Additionally, the hinged ankle brace significantly reduced knee anterior shear forces compared with the lace-up brace both during the deceleration phase and at peak ankle dorsiflexion (mean difference, 0.8 N/kg [P = .018] and 0.9 N/kg [P = .011], respectively). Conclusion: The hinged ankle brace significantly reduced ankle inversion compared with the no-brace condition and reduced ankle and knee joint forces compared with the lace-up brace in a female basketball population during a cutting task. Compared with the lace-up brace, the hinged brace may be a better choice of prophylactic ankle support for female basketball players from a biomechanical perspective. However, both braces increased knee internal rotation and knee abduction angles, which may be problematic for a population that already has a high prevalence of knee injuries.

The prevalence and severity of injuries in field hockey drag flickers: a retrospective cross-sectional study

ABSTRACT The drag flick is the preferred method of scoring during a penalty corner in field hockey. Performing the drag flick requires a combination of strength, coordination and timing, which may increase susceptibility to injuries. However, injury prevalence in drag flickers has not previously been investigated. Therefore, this study compared the injury prevalence and severity of lower limb and lower back injuries between drag flickers and non-drag flickers in field hockey. A total of 432 local, national and international adult field hockey players (242 males, 188 females) completed an online questionnaire to retrospectively determine the 3-month prevalence and severity of ankle, knee, hip and lower back injuries. Of this group, 140 self-identified as drag flickers and 292 as non-drag flickers. The results showed that drag flickers had significantly higher prevalence of hip (OR: 1.541; 95% CI: 1.014, 2.343) and lower back injury (OR: 1.564; 95% CI: 1.034, 2.365) compared to non-drag flickers. No significant differences were observed between drag flickers and non-drag flickers in injury prevalence at the ankle and knee. There were no significant between-group differences in injury severity scores. Overall, the prevalence of hip and lower back injuries was significantly higher in drag flickers compared to non-drag flickers.

How Young Girls Change Their Landing Technique Throughout the Adolescent Growth Spurt

Background: Despite the rapid musculoskeletal changes experienced by girls throughout the adolescent growth spurt, little is known about how their lower limb landing technique changes during this time. Purpose: To investigate the longitudinal changes in the 3-dimensional lower limb kinematics, joint moments, and muscle activation patterns displayed by girls when performing a horizontal landing task throughout their adolescent growth spurt. Study Design: Descriptive laboratory study. Methods: A total of 33 healthy 10- to 13-year-old girls, in Tanner stage II, with a maturity offset of −6 to −4 months (time from peak height velocity) were recruited. According to her maturity offset, each participant was tested up to 4 times during the 12 months of her growth spurt (maturity offset: test 1 = −6 to −4 months; test 2 = 0 months; test 3 = 4 months; test 4 = 8 months). During each test session, participants performed a horizontal leap movement, during which ground-reaction forces (1000 Hz), lower limb muscle activity (1000 Hz), and kinematic data (100 Hz) were collected. Results: Throughout the growth spurt, girls displayed a decrease in knee flexion (P = .028), increase in hip flexion (P = .047), increase in external knee abduction moments (P = .008), and decrease in external hip adduction moments (P = .003) during the landing movement. Conclusion: During their adolescent growth spurt, pubescent girls displayed a change in the strategy with which they controlled their lower limb to land after performing a horizontal leap movement. This change in the landing strategy has the potential to increase the risk of anterior cruciate ligament injuries toward the latter stages of the adolescent growth spurt. Clinical Relevance: The outcomes of this research provide a greater understanding of the changes in the landing strategy used by pubescent girls throughout the adolescent growth spurt. This can assist in the development of screening tools designed to determine “at-risk” landing biomechanics during puberty.

Does skill specialisation influence individual differences in drag flicking speed and accuracy

ABSTRACT Research has revealed that individual soccer goalkeepers respond differently to penalty shots, depending on their specific perceptual and motor capabilities. However, it remains unclear whether analogous differences exist between individual penalty takers, and if specialising in penalty taking affects the occurrence of differences between individuals. The present study examined individual differences in penalty shot speed and accuracy for specialists in penalty taking versus non-specialists. Expert specialist field hockey drag flickers and equivalently skilled non-specialists performed drag flicks towards predetermined targets placed in the face of a standard field hockey goal. Comparisons in shot speed and accuracy were made at a group level (specialists vs. non-specialists) as well as between individuals. Results revealed differences in both speed and accuracy between specialists, but only differences in speed between non-specialists. Specialists generated significantly greater shot speed than non-specialists (P < .001) and were more accurate to some, but not all, targets (top left, P < .006, bottom left P < .001). In addition, it was found that in specialists increasing practice correlated with decreasing accuracy. This may indicate that excessive practice could potentially reduce a specialist’s accuracy in shooting towards specific targets.

Differences in lower limb biomechanics between ballet dancers and non-dancers during functional landing tasks

OBJECTIVES To determine the differences in the lower limb landing biomechanics of adolescent ballet dancers compared to non-dancers when performing a hop and a stop jump task. DESIGN Cross-sectional. SETTING Laboratory. PARTICIPANTS Thirteen adolescent female ballet dancers (11.8 ± 1.1 years) and 17 non-dancers (10.9 ± 0.8 years) performed hop and stop jump tasks. MAIN OUTCOME MEASURES Vertical ground reaction force, and three-dimensional ankle, knee and hip joint angles and moments during the landing phase. RESULTS Dancers displayed greater sagittal plane joint excursions during the hop and stop jump at the ankle (mean difference = 22.0°, P < 0.001, 14.8°, P < 0.001 respectively), knee (mean difference = 18.1°, P = 0.001, 9.8°, P = 0.002 respectively) and hip (stop jump task; mean difference = 8.3°, P = 0.008). Dancers displayed a larger hip extensor moment compared to non-dancers (P < 0.001) during the stop jump task only. Dancers also took longer to reach peak vGRF and jumped three times higher than non-dancers (P < 0.001) during the stop jump task. No difference in peak vGRF between groups was displayed for either task. CONCLUSIONS Adolescent dancers demonstrate a transfer of landing technique to non-ballet specific tasks, reflective of the greater jump height and sagittal plane joint excursions. This landing strategy may be associated with the low rate of non-contact ACL injuries in female dancers.

Effect of prophylactic ankle taping on ankle and knee biomechanics during basketball-specific tasks in females

OBJECTIVE The aim of this study was to investigate the effects of ankle taping on ankle and knee joint biomechanics during cutting and rebound activities in females. DESIGN Cross-sectional. SETTING Laboratory. PARTICIPANTS Twenty semi-professional female basketball players performed a cut and rebound task under two conditions (taped and no-tape). MAIN OUTCOME MEASURES Kinematic and ground reaction force data were collected during the deceleration phase of each movement task. RESULTS Taping resulted in a significant reduction in peak ankle dorsiflexion, inversion and internal rotation angles and range of motion (ROM) at the ankle joint; and reduced knee ROM in the sagittal plane during the rebound task only. Taping significantly reduced peak knee flexion moment (0.29 Nm/kg, P = 0.013) and increased knee internal rotation moment (0.63 Nm/kg, P = 0.026) during the cutting task compared to control. Taping also significantly reduced the internal rotation moment (0.07 Nm/kg, P = 0.025), and medial shear forces (0.14 N/kg, P = 0.012) in the rebound task. CONCLUSION Results of the study suggest that ankle taping restrict ankle range of movement in the rebound task only and ankle taping appears to have upstream effects on the knee, which may have injury implications.