Lumbopelvic-Hip Complex Contribution During Lower Extremity Screening Tests in Elite Figure Skaters

ABSTRACT Context: Figure skating requires power and stability for take-off and landing from multi-rotational jumps and various on-ice skills. Repetitive forces may cause overuse injuries distally making lumbopelvic-hip endurance, strength, and neuromuscular control imperative. Objective: The purpose was to compare lumbopelvic-hip endurance and neuromuscular control in elite figure skaters between sex and limbs using common screening tests. Design: Cross-sectional study. Setting: U.S. Olympic and Paralympic Training Center. Participants: Forty elite figure skaters (23.2±4.3 years, 169.1±12.2 cm, 20F, 40R landing limb) performed the Y-balance test, single leg squat (SLS), single leg squat jump (SLSJ), and unilateral hip bridge endurance test. Main Outcome Measures: Normalized reach difference (% of leg length) and composite scores (((Anterior + Posteromedial + Posterolateral)/Limb length x 3) x100) were calculated for Y-balance test. Skaters held the unilateral hip bridge until failure with a maximum allotted time of 120s. Participants performed 5 SLS and SLSJ, barefooted with the contralateral limb held behind them to mimic a landing position. Both tests were scored by the number of times the patella moved medially to the first ray (medial knee displacement (MKD)). MANOVA with post-hoc independent t-tests were performed between groups and sex. Paired t-tests were used to analyze limb differences. Results: Females had a larger composite Y-balance score (R:+10.8, p=.002; L:+10.5, p=.001) and hip bridge hold time (R:+26.4 sec, p=.004; L:+28.2 sec, p=.002) on both limbs compared to males. Males held the hip bridge longer on their landing limb. During the SLS and SLSJ, 6 skaters performed worse on their non-landing limb during the SLS, and 11 skaters had no MKD with either test. Conclusions: Females performed better on the Y-balance and unilateral hip bridge tests. Increased MKD for some skaters in the SLS and SLSJ may indicate hip abductor weaknesses. Understanding proximal lumbopelvic-hip variables during take-off and landing may elucidate contributing factors to distal overuse injuries.

The ACL can hypertrophy in response to mechanical loading: an MRI study in elite athletes (157)

Objectives: Several morphological risk factors for anterior cruciate ligament (ACL) injury have been identified,1,6,12,13 including the size of the ACL.5,8,12,15 A smaller ACL volume and diameter are associated with a greater risk of injury when comparing ACL-injured subjects to matched controls.5,8,12,15 Although morphological risk factors as a group have been largely characterized as non-modifiable,9,10 ACL surface and cross-sectional areas (CSA) have the potential for modifiability, especially during growth and development.7,11 These ACL area measures have increased and the mechanical properties of the ACL have improved following exercise through periods of growth in animal models.2,7,11,14 In humans, we are only aware of one study of ACL hypertrophy—a small study of elite weightlifters.7The main purpose of this study, therefore, was to determine whether the ACL can hypertrophy in response to mechanical loading by comparing bilateral differences in ACL CSA in athletes who habitually load one leg more than the other in training for their sport. Based on the work of Grzelak et al. in weightlifters,7 as well as animal evidence that the ACL responds to exercise,2,11,14 we hypothesized that these athletes would present with significantly greater ACL CSAs in the landing/drive leg, the knee that is loaded the most in comparison with the contralateral control knee. Demonstrating the potential for the ACL to hypertrophy via mechanical loading would provide a scientific basis for exploring ACL injury prevention strategies aimed at increasing ACL CSA and robustness given that a small ACL volume and diameter are known risk factors for injury. This is particularly important for all children and especially females since they are at a much higher risk for ACL injury, and thereafter the development of knee osteoarthritis. Methods: We recruited 50 figure skaters and springboard divers because they consistently and repeatedly use one leg more than the other, thereby ensuring that one knee was habitually loaded more than the other (Table 1). More specifically, figure skaters always land their jumps on the same leg, while springboard divers always drive the same leg (‘drive’ leg) into the board during their hurdle approach. Sport training for all participants began prior to puberty and continued through and after. Bilateral knee magnetic resonance images (MRIs) were acquired with a Philips Ingenia 3.0-T scanner using a dedicated knee coil. Each knee, resting in slight flexion in the coil, was scanned using three sequences, all in the plane of the ACL: (1) oblique-sagittal (repetition time (TR): 5100 ms; echo time (TE): 30 ms; slice thickness: 2.5 mm; pixel spacing: 0.19 x 0.19 mm); (2) oblique-coronal (TR: 4000 ms; TE: 30 ms; slice thickness: 2.5 mm; pixel spacing: 0.20 x 0.20 mm); (3) oblique-axial (TR: 5100 ms; TE: 30 ms; slice thickness: 2.5 mm; pixel spacing: 0.20 x 0.20 mm). Using the oblique-axial-plane scans, the ACL CSA was measured on the three slices that were closest to 50% of the ligament’s length, and then averaged (Figure 1). Using the oblique-sagittal-plane scans, which were reconstructed to run parallel to the patellar tendon, the anteroposterior diameter of the patellar tendon was measured perpendicular to the tendon’s longitudinal axis at a distance of 2 cm distal to the patella3,4 on the slice displaying the thickest part of the tendon at that height (Figure 2). In addition, isometric and isokinetic knee extensor and knee flexor peak torques were acquired using a dynamometer. Bilateral differences in ACL CSA, PT diameter, and knee muscle strength were evaluated via one-sample t-tests that compared the mean percent difference between limbs to a null hypothesis of a zero mean percent difference. Correlations between bilateral ACL CSA differences, age of training onset and years of training were also examined. Results: Athletes with repeated unilateral lower limb loading had significantly greater ACL CSAs in the dominant knee than the non-dominant knee (Table 1; ACL CSAs: dominant = 42.0 ± 8.8 mm2; non-dominant = 40.8 ± 9.1 mm2; % difference = 4.4 ± 13.8%; t = 2.236; p = 0.030). Also, these athletes had significantly greater AP patellar tendon diameters in the dominant knee than the non-dominant knee (Table 1; patellar tendon diameters: dominant = 4.1 ± 0.6 mm; non-dominant = 3.9 ± 0.5 mm; % difference = 4.5 ± 9.4%, t = 3.322; p = 0.002). The percent bilateral difference in ACL CSA, however, was not associated with training onset (r = 0.087, p = 0.553) or years of training (r = -0.068, p = 0.641). Lastly, isometric knee flexor peak torques were significantly greater in the landing/drive leg than the contralateral knee (Table 2). Peak torques from other contraction types or muscle group did not differ between limbs (Table 2). Conclusions: Athletes who habitually loaded one leg more than the other prior to, during and after puberty exhibited significant unilateral ACL hypertrophy in their landing/drive leg. These results support existing evidence that exercise, including resistance and endurance regimens, during periods of pubertal growth has the potential to increase ACL CSA and, therefore, its strength.2,7,14 This suggests that perhaps the ACL could be ‘trained’ to become larger, more robust, and thus at lower risk of injury given that a smaller ligament is associated with a greater risk of injury. The bilateral difference in patellar tendon morphology supports our assumption that the athletes participating in this study consistently loaded one knee more than the other during their sport training, and that increased loading led to the hypertrophy of two important structures in that knee. Many gaps in knowledge—ACL development during growth and how exercise may alter its morphology and mechanical properties—need to be addressed as injury prevention strategies that involve ‘training’ the ACL are explored.

Determinants of Sports Injury in Young Female Swedish Competitive Figure Skaters

Introduction: Although figure skating attracts several hundred thousand participants worldwide, there is little knowledge about physical health and sports injuries among young skaters. The present study aimed to describe the health status of a geographically defined Swedish population of licensed competitive figure skaters and to examine injury determinants.Methods: All licensed competitive skaters in the southeastern region of Sweden were in April 2019 invited to participate in a cross-sectional study using an online questionnaire. Multiple binary logistic regression was used for the examination of injury determinants. The primary outcome measure was the 1-year prevalence of a severe sports injury episode (time loss >21 days). The secondary outcome measure was the point prevalence of an ongoing injury. The determinants analyzed were age, skating level, relative energy deficiency indicators, and training habits.Results: In total, 142 (36%) skaters participated, 137 (96%) girls [mean (SD) age: 12.9 (SD 3.0) years]. Participating boys (n = 5) were excluded from further analysis. The 1-year prevalence of a severe sports injury episode was 31%. The most common injury locations for these injuries were the knee (25%), ankle (20%), and hip/groin (15%). In the multiple model, having sustained a severe injury episode was associated with older age (OR 1.2, 95% CI 1.1–1.4; p = 0.002) and an increased number of skipped meals per week (OR 1.1, 95% CI 1.0–1.3; p = 0.014). The point prevalence of an ongoing injury episode was 19%. The most common locations were the knee (24%), ankle (24%), and foot (24%). Having an ongoing injury episode was associated with older age (OR 1.4, 95% CI 1.2–1.7; p < 0.001) and an increased number of skipped meals per week (OR 1.1, 95% CI 1.0–1.3; p = 0.049).Conclusion: One-third of young female Swedish competitive figure skaters had sustained a severe injury episode during the past year, and a fifth reported an ongoing episode. Older age and an increased number of skipped meals per week were associated with a sports injury episode. Long-term monotonous physical loads with increasing intensity and insufficient energy intake appear to predispose for injury in young female figure skaters. Further examination of injury determinants among competitive figure skaters is highly warranted.

Biomechanics of Rotational Movement in Off-Ice Figure Skating Jumps: Applications to Training

Introduction The aim of this study was to characterize kinematic parameters of the rotational body movement during the office figure skating multi-revolution jumping exercise and to propose applications to training. Material and Methods Six elite Polish female junior singles figure skaters were examined performing single and their respective maximum total rotation vertical jumps in off-ice conditions. Measurements of the ground reaction force were performed with a KISTLER (500 Hz) piezoelectric sensor platform with BioWare Software, synchronized with the cinematographic analysis using the Vicon T-Series motion capture system. Results The analysis revealed positive linear relations between selected jump parameters of the pre-take-off phase and after the landing. Two moments of countering torque were also noticed: the first in the landing phase, and the second before reaching the stabilized position. Conclusions Applications of the findings for off-ice training were discussed.