Functional hamstrings: quadriceps ratios in elite women's soccer players

The hamstrings to quadriceps functional ratio expressed over the full angle-angular velocity range using a limited number of data points

The hamstring to quadriceps (H : Q) strength ratio is widely used to identify individuals at risk of sustaining hamstring strain injuries. However, its efficacy is not supported by the current evidence. Current methods for the calculation of the H : Q ratio provide only a one- or two-dimensional ratio, often ignoring fundamental muscle mechanical properties. Based on isokinetic torque measurements of the knee flexors and extensors (0-400° s^-1) in 25 young, physically active males, we derived a model equation that creates a three-dimensional H : Q functional ratio profile. The model robustness was tested against a different number of input torque data (8, 11, 14 and 17 pairs of points) and small perturbation of the knee joint angle data (5°). The model was consistent and behaved well under all conditions apart from the eight pairs of points (R ² = 0.84-0.96; RMSE = 0.14-0.25; NRMSE = 0.12-0.27), and the H : Q functional ratio was successfully described even at angles and velocities that cannot be normally assessed with isokinetic dynamometry. Overall, our results suggest that the model can provide a fast and accurate three-dimensional description of the knee joint muscle strength balance using as few as 11 experimental data points and this could be an easy-to-employ screening tool.

Are There Differences in Concentric Isokinetic Strength Perfor-Mance Profiles between International and Non-International Elite Soccer Players?

The purpose of this study is to evaluate the differences in concentric isokinetic strength characteristics of the knee extensor and knee flexor musculature between international (IL) and non-international level (N-IL) soccer players. The second aim is to establish strength symmetry status in knee muscles for dominant (DL) and non-dominant (NDL) legs for both within and between groups. 100 male top elite soccer players (IL: n = 36, age = 27.5 ± 3.4 years and N-IL: n = 64, age = 27.7 ± 6.4 years) underwent concentric isokinetic strength tests, using a Biodex System 3 dynamometer. Results indicate that statistically significant differences between groups were noted for peak torque of hamstrings (PT-H), hamstrings/quadriceps (H/Q) ratio, and total work of hamstrings (TW-H), where mean values for the IL were similarly higher than for the N-IL group (p = 0.006, p < 0.001, and p = 0.012, respectively). Our results also showed statistically significant differences for peak torque of quadriceps (PT-Q), PT-H, total work of quadriceps (TW-Q) and TW-H between legs, where mean values noted for the DL were higher than for the NDL for both groups (p = 0.021, p < 0.001, p = 0.006, and p = 0.004, respectively). Additional results show that IL players presented more symmetrical strength between legs than N-IL. The results of this study indicate that that the greatest differences in isokinetic strength performance across players at different soccer levels relate to the hamstring muscle. As a result, systematic strength training of these muscle groups is strongly recommended.

Contextual factors influencing the characteristics of female football players

Women's football participation rates are projected to increase to 60 million worldwide by 2026, doubling the current participation. Growing investment and the increase in research in women's football has had a positive effect on the level of performance over the last 10 years. The present review aimed to examine the literature on the physical and physiological characteristics of female football players from 2010 to 2019 to reflect the recent changes in professionalism. Characteristics investigated include anthropometry, strength, speed, endurance, power, change of direction and repeated sprint ability. These characteristics are presented in relation to playing position, age and competition-level. Results revealed that goalkeepers (171 cm, 66 kg) and defenders (168 cm, 61 kg) were the tallest and had the greatest body mass, while attackers were the fastest players over 20 m (3.05 s) and 30 m (4.38 s) and midfielders had the highest endurance (55.4 mL∙kg^-1∙min^-1) (P<0.05). Characteristics tended to improve with age until full biological maturity around 17 to 18 years of age. Competition comparisons demonstrated international players have significantly greater speed, repeated sprint ability, power and endurance characteristics (P<0.05). By identifying influential factors, coaches may be able to optimize their training and physical assessment practices, to better expose players to the required stimulus to develop these characteristics considered crucial to improved performance.

Age-related differences in torque in angle-specific and peak torque hamstring to quadriceps ratios in female soccer players from 11 to 18 years old: Α Cross-sectional study

The aim of this study was to evaluate and compare the hamstring (H) and quadriceps (Q) strength, bilateral difference and balance ratios in female soccer players. Ninety-three athletes from three age groups: under 13 (U13), 15 (U15) and 18 (U18) participated in the study performing isokinetic tests to measure peak torque, total work, average power and torque at 30º of thigh muscles. Conventional strength balance ratios, angle-specific balance ratio and bilateral strength difference were evaluated. There was bilateral strength difference for extensor muscles total work (p = 0.02) in U13 and flexor muscles peak torque (p = 0.02) in U15. All variables were superior in U15 than U13 (p <.05). There was no strength difference between U15 and U18. Balance ratios did not differ between sides or age groups. The study showed that although peak torque values were higher in U15 than in U13, balance ratios were similar.

Relationships between Hamstrings-to-Quadriceps Ratio and Variables Describing Countermovement and Drop Jumps

The impact of the hamstrings-to-quadriceps ratio on sport movement performance has not been sufficiently described. However, it seems that in movements involving eccentric-concentric muscular contractions, a higher hamstrings-to-quadriceps ratio should have a positive impact on human movement performance. The present study is aimed at identifying relationships between the hamstrings-to-quadriceps ratio and variables describing countermovement and drop jumps. The study was carried out in a group of 14 female soccer players. The tests were conducted using a Kistler force plate, an SG electrogoniometer, and the Biodex System 4 Pro dynamometer. Each player performed three countermovement jumps (CMJ) and three drop jumps (DJ) from heights of 15, 30, 45, and 60 cm. The peak torques of knee extensors and flexors were measured in isometric conditions and in isokinetic conditions at angular velocities of 30^o/s, 60^o/s, 90^o/s, and 120^o/s. Statistically significant relationships were found between the variables that describe CMJ, DJ 15, DJ 30, and hamstrings-to-quadriceps ratio at some, though not all, of the angular velocities measured. No significant relationships were found between the hamstrings-to-quadriceps ratio and variables that describe DJ 45 and DJ 60. The heights of CMJ, DJ 15, and DJ 30 were increased with higher hamstrings-to-quadriceps ratios. Analogous relationships were found between the hamstrings-to-quadriceps ratio and relative mechanical power during the take-off phase of the CMJ. Significant relationships between the hamstrings-to-quadriceps ratio and variables that describe vertical jump are likely to be observed if adequate angular velocity is used in the measurement of muscle torque.

The isokinetic strength profile of elite soccer players according to playing position

The aim of this study was to compare isokinetic strength performance profiles in elite soccer players across different field positions. A total of 111 elite international players of Polish Ekstraklasa (the top division in Poland) were examined during the 2010–2015 seasons. The players were classified into six positional roles: central defenders (CD), external defenders (ED), central midfielders (CM), external midfielders (EM), forwards (F), and goalkeepers (G). The concentric isokinetic strength (peak torque [PT] of quadriceps and hamstrings, H/Q ratios) was calculated for the dominant leg and the non-dominant leg at angular velocity of 1.05 rad ·s^–1, whereas to assess isokinetic muscle endurance, the total work [TW] at angular velocity of 4.19 rad ·s^–1, was taken into consideration. The results showed that isokinetic strength performance varies significantly among players in different playing positions. The analysis of PT for quadriceps (PT-Q) and hamstrings (PT-H) generally showed that the goalkeepers and central midfielders had lower strength levels compared to other playing positions. In the case of PT-H and hamstring/quadricep (H/Q) peak torque ratios, statistically significant differences were also noted for the legs, where mean values noted for the dominant leg were higher than for the non-dominant leg. For TW for quadriceps (TW-Q) and hamstrings (TW-H), statistically significant differences were noted only between playing positions. TW-Q values for goalkeepers were lower than for central defenders and external midfielders. TW-H values for goalkeepers were lower than for central midfielders, central defenders and external midfielders. This study showed that specific functional activity of players in individual positions on the field influences the varied profile of isokinetic strength performance.

Functional performance 2-9 years after ACL reconstruction: cross-sectional comparison between athletes with bone-patellar tendon-bone, semitendinosus/gracilis and healthy controls

PURPOSE

The purpose of this cross-sectional study was to provide descriptive data on functional performance in men and women with ACLR, to compare bone-patellar tendon-bone (BPTB) with semitendinosus/gracilis (STG) within the same sex and to compare the ACLR subjects with healthy controls.

METHODS

Eligible participants comprised 100 men (43 % BPTB) and 84 women (41 % BPTB) after ACLR, of whom 30 men (STG n = 19; BPTB n = 11) and 18 women (STG n = 12; BPTB n = 6) were untraceable/not willing and 15 men (STG n = 9; BPTB n = 6) and 18 women (STG n = 12; BPTB n = 3) were not able to take part in the measurements because of injury. Besides men BPTB (n = 24), men STG (n = 27), women BPTB (n = 23) and women STG (n = 23), healthy men (n = 22) and women (n = 22) participated. Measurements consisted of questionnaires, isokinetic peak torque and endurance tests, a hop test battery and drop jump including video analysis.

RESULTS

Only the occurrence of dynamic knee valgus differed between ACLR and healthy subjects.

CONCLUSION

Two to nine years after ACLR, 16 % of athletes could not participate because of a lower extremity injury. In the remaining group, this study showed similar results for males and females with BPTB compared with STG. Also, similar results are found for quantity of movement comparing operated and healthy subjects. For quality of movement, only the occurrence of dynamic knee valgus in landing from a jump is higher in operated subjects compared with healthy controls. This supports the relevance of a focus on quality of movement as part of ACLR rehabilitation programmes and return to sports criteria.

LEVEL OF EVIDENCE

III.

The Effects of Angular Velocity and Training Status on the Dynamic Control Equilibrium

Thigh muscle imbalances may impair sports performance and cause injuries. Common diagnostic parameters of knee muscle balance lack practical applicability. This cross-sectional study aimed to evaluate the effects of angular velocity and training status on the dynamic control ratio at the equilibrium point representing the intersection of eccentric knee flexion and concentric knee extension moment-angle curves. 58 trained and 58 untrained male participants (22.1 years, 82.4 kg) performed concentric and eccentric knee flexions (prone position) and extensions (supine position) on an isokinetic dynamometer operating at 30 and 150°/s. Trained participants had significantly higher DCRe moments at all angular velocities compared with their untrained counterparts (trained _30,150 : 1.86, 1.90 Nm/kg; untrained _30,150 : 1.56, 1.60 Nm/kg; p<0.001, partial η²=0.345). Dynamic control equilibrium moments rose with increasing velocity (p=0.001, partial η²=0.095), whereas dynamic control equilibrium angles (trained _30,150 : 28.9, 30.8°; untrained _30,150 : 26.1, 27.0°) were influenced by training status (p=0.004, partial η²=0.072), but not by angular velocity (p=0.241, partial η²=0.012). Dynamic control equilibrium parameters detect thigh muscle balance and reflect the trained participants' capacity to resist high eccentric knee flexor moments, especially during fast movements. Direct links to muscular loading during sprinting are conceivable, but warrant further investigation. The assessment of dynamic control equilibrium moments and angles might help physiotherapists and coaches to improve functional muscle screening, injury prevention and purposeful return to sport.

Correlation between quadriceps to hamstring ratio and functional outcomes in patellofemoral pain

BACKGROUND

The aim of this study was to investigate the correlation between quadriceps to hamstring (Q:H) ratio and the functional outcomes in Patellofemoral Pain (PFP) patients.

METHODS

The study included forty-four women diagnosed with unilateral PFP. Eccentric and concentric quadriceps and hamstring strength were recorded. Conventional Q:H ratio was calculated as the concentric quadriceps to concentric hamstring peak torque (Ratio 1). Functional ratios were calculated as the eccentric quadriceps to concentric hamstring peak torque (Ratio 2) and as the concentric quadriceps to eccentric hamstring torque (Ratio 3). Functional levels of the patients were determined by using Kujala scores, hop test and step test. Pain levels during activities were recorded. The relationship among Ratio 1, Ratio 2 and Ratio 3 with functional outcomes and pain levels were evaluated using Spearman's correlation coefficient test.

RESULTS

Eccentric and concentric quadriceps and hamstring strength were lower on involved side than uninvolved side. Ratio 2 correlated stronger with Kujala score (r=0.69) than Ratio 1 (r=0.49) and Ratio 3 (r=0.30). Step test (r=0.35) and hop test (r=0.38) only correlated with Ratio 2. Pain levels correlated more with Ratio 2 (r values ranged between 0.38 and 0.48).

CONCLUSION

Eccentric quadriceps to concentric hamstring ratio was observed more related to the functional outcomes and painful activities in patients with PFP.

LEVEL OF EVIDENCE III

Cross-sectional study.

Effects of age and muscle action type on acute strength and power recovery following fatigue of the leg flexors

Short-term strength and power recovery patterns following fatigue have received little research attention, particularly as they pertain to age-specific responses, and the leg flexors (i.e., hamstrings) muscle group. Thus, research is warranted addressing these issues because both age-related alterations in the neuromuscular system and mode of muscle action (e.g., eccentric, concentric, isometric) may differentially influence recovery responses from fatigue. The aim of this study was to investigate the strength and power recovery responses for eccentric, concentric, and isometric muscle actions of the leg flexors in young and older men following an isometric, intermittent fatigue-inducing protocol. Nineteen young (age = 25 ± 3 years) and nineteen older (71 ± 4) men performed maximal voluntary contractions (MVCs) for eccentric, concentric, and isometric muscle actions followed by a fatigue protocol of intermittent (0.6 duty cycle) isometric contractions of the leg flexors at 60% of isometric MVC. MVCs of each muscle action were performed at 0, 7, 15, and 30 min following fatigue. Peak torque (PT) and mean power values were calculated from the MVCs and the eccentric/concentric ratio (ECR) was derived. For PT and mean power, young men showed incomplete recovery at all time phases, whereas the older men had recovered by 7 min. Eccentric and isometric muscle actions showed incomplete recovery at all time phases, but concentric recovered by 7 min, independent of age. The ECR was depressed for up to 30 min following fatigue. More rapid and pronounced recovery in older men and concentric contractions may be related to physiological differences specific to aging and muscle action motor unit patterns. Individuals and clinicians may use these time course responses as a guide for recovery following activity-induced fatigue.

Neuromuscular interactions around the knee in children, adults and elderly

Although injury and neuromuscular activation patterns may be common for all individuals, there are certain factors which differentiate neuromuscular activity responses between children, adults and elderly. The purpose of this study is to review recent evidence on age differences in neural activation and muscle balances around the knee when performing single joint movements. Particularly, current evidence indicates that there are some interesting similarities in the neuromuscular mechanisms by which children or the elderly differ compared with adults. Both children and elderly display a lower absolute muscle strength capacity than adults which cannot fully be explained by differences in muscle mass. Quadriceps activation failure is a common symptom of all knee injuries, irrespective of age but it is likely that its effect is more evident in children or adults. While one might expect that antagonist co-activation would differ between age categories, it appears that this is not the case. Although hamstring: quadriceps ratio levels are altered after knee injury, it is not clear whether this is an age specific response. Finally, evidence suggests that both children and the elderly display less stiffness of the quadriceps muscle-tendon unit than adults which affects their knee joint function.