Testing the Posterior Chain: Diagnostic Accuracy of the Bunkie Test versus the Isokinetic Hamstrings/Quadriceps Measurement in Patients with Self-Reported Knee Pain and Healthy Controls.

(1) Background: The isokinetic measurement (IM) of the leg muscles is well established but costly, whereas the Bunkie Test (BT) is a rarely investigated but easy-to-conduct functional test to evaluate the total posterior chain. Although the tests differ in aim and test structures, both have their justification in the assessment process. Therefore, this study evaluated the diagnostic accuracy of the BT and the IM. (2) Methods: 21 participants (9 female, 12 male; age, 26.2 ± 5.26 years; weight 73.8 ± 14.6 kg; height 176.0 ± 9.91 cm) and 21 patients (9 female, 12 male; age, 26.5 ± 5.56 years; weight, 72.6 ± 16.9 kg; height 177.0 ± 10.1 cm) with self-reported pain in the knee performed the IM and the BT. For IM, we calculated the ratio of the knee mean flexor/extensor peak torque (H/Q ratio) for 60°/s and 120°/s, and BT performance was measured in seconds. We classified the IM (<0.6 H/Q ratio) and the BT (leg difference ≥4 s) as binary results according to the literature. We calculated the sensitivity and specificity, which we compared with the Chi-Square test, and the 95% confidence intervals (CI). A p-value of ≤0.05 is considered significant. (3) Results: The sensitivity for the BT was 0.89, 95% CI [0.67, 0.99], and the specificity was 0.52 [0.30, 0.74]. For the IM, the sensitivity was 0.14 [0.03, 0.36] for 60°/s and 0.05 [0.00, 0.24] for 120°/s, and the specificity was 0.70 [0.46, 0.88] for 60°/s and 0.90 [0.68, 0.99] for 120°/s. The results of the Chi-Square tests were significant for the BT (χ2 (1) = 6.17, p = 0.01) but not for the IM (60°/s: χ2 (1) = 0.70, p = 0.40; 120°/s: χ2 (1) = 0.00, p = 0.97). (4) Conclusions: Patients were more likely to obtain a positive test result for the BT but not for the IM.

Muscle Strength and Hamstrings to Quadriceps Ratio in Young Soccer Players: A Cross-Sectional Study.

The aim of the present study was to examine and compare the concentric isokinetic peak torque of the knee flexors and extensors muscles, as well as their ratio, in young soccer players. Two hundred and sixty-five (n = 265) young soccer players were divided into five groups: U-12 (n = 43, mean age 11.5 ± 0.4 yrs), U-14 (n = 63, mean age 13.6 ± 0.3 yrs), U-16 (n = 64, mean age 15.4 ± 0.5 yrs), U-18 (n = 53, mean age 17.5 ± 0.4 yrs) and U-20 (n = 42, mean age 19.3 ± 0.6 yrs). Three maximal voluntary isokinetic leg extensions and flexions at angular velocities of 60, 180, and 300°·s-1, and H:Q strength ratio was determined. The largest H:Q strength ratio for all ages, with the exception of age group U-12, appears at a slow angular velocity of 60°·s-1, and the smallest H:Q ratio at a fast angular velocity of 300°·s-1. In age group U-12, at an angular velocity of 60°·s-1, the strength of the quadriceps muscle was almost twice the strength of the hamstrings. The H:Q strength ratio was smaller in age group U-12 and greater in group U-20. In age group U-12, the greatest H:Q strength ratio appeared at an angular velocity of 180°·s-1, while in the other age groups, it appeared at 60°·s-1. Strength training of hamstring muscles remains inadequate across ages. The small H:Q strength ratio in younger ages and the large H:Q ratio in older ages suggest that high-intensity training may increase the H:Q strength ratio, which, in turn, may protect the knee joint from excessive and burdensome loads.

Inter-limb asymmetries and kicking limb preference in English premier league soccer players.

The aims of this study were: (1) to quantify interlimb asymmetries in EPL soccer players in the context of kicking limb preference and (2) to establish the relationship between interlimb asymmetries and measures of physical performance. Twenty-two players (age: 21.8 ± 4.4 years) from an EPL club performed a running gait assessment (20 km/h) and unilateral countermovement jumps, a CoD assessment (modified 505 test), and an isokinetic knee extension/flexion protocol using each leg. Asymmetries were quantified using the percentage difference method and Pearson's correlations were used to quantify the association between variables. Players displayed the greatest level of asymmetry in isokinetic strength measures (5.9-12.7%) and lower levels of asymmetry in gait (1.6-7.7%), jump (0.9-7.0%) and CoD (1.9-3.5%) assessments. The influence of the preferred kicking limb was most evident in the isokinetic assessment with the players showing dominance in the preferred limb for knee flexor strength and in the non-preferred limb for knee extensor strength. These manifested in the asymmetry values calculated for the hamstring:quadricep (H:Q) ratios at 60°/s (8.80 ± 7.82%) and 240°/s (11.22 ± 7.04%) and in the functional H:Q ratio (12.67 ± 8.25%). The asymmetry values for peak extensor moment at 240°/s showed a significant correlation (ρ = -0.55, p = 0.034) with 10 m time in the CoD assessment. These findings provide benchmark asymmetry data for soccer practitioners and reveal that kicking limb preferences may bring about interlimb differences in the H:Q ratio which raises important considerations in the design of testing batteries and injury reduction interventions.

The Relationship between the Hamstring-to-Quadriceps Ratio and Jumping and Sprinting Abilities of Young Male Soccer Players.

The correct torque ratio between the knee joint extensor and flexor muscle groups can effectively prevent injuries to the anterior cruciate ligament and hamstring strain. However, it is unclear whether a high torque ratio of the knee joint flexor muscles to the extensor muscles is beneficial for sport performance. Therefore, the aim of the study was to investigate the relationship between the hamstring-to-quadriceps (H/Q) ratio and sprint times (10- and 30-m) and jump heights (CMJ-countermovement jump and SJ-squat jump) in soccer players. The study examined 26 young elite soccer players (age: 18.1 ± 0.7 years; body height: 1.77 ± 0.05 m; body mass: 72.7 ± 5.7 kg). Knee joint flexor and extensor peak torques were assessed using the Cybex dynamometer (at 60°/s, 120°/s and 180°/s). Additionally, each participant performed the CMJ, SJ, and 30 m sprint. A significant relationship was obtained between the H/Q ratio (60°/s) and 30 m sprint time (r = 0.47). The positive direction of this relationship may indicate an important role of knee joint extensors in sprinting performance. Moreover, the H/Q ratio was not significantly associated with the CMJ, SJ or 10 m sprint performance. The H/Q ratio should be considered together with the peak torque values in terms of the assessment of sprinting and jumping performance.

The relationships between knee extensors/ flexors strength and balance control in elite male soccer players.

BACKGROUND: Strength and balance are important factors for soccer players to be successful. This study's aim was to determine the relationship between lower-limb muscle strength and balance control in elite male soccer players (n = 77). METHODS: Concentric isokinetic strength (peak torque of quadriceps (PT-Q) and hamstrings (PT-H), hamstrings/quadriceps (H/Q) ratio) was measured for the dominant and non-dominant leg at angular velocities of 60°s-1and 240°s-1, as well as the total work for extensors (TW-Q) and flexors (TW-H) for both legs (at an angular velocity of 240°s-1only). Balance score (BAL score) was used for unilateral assessment of balance control using a Delos Postural System Test measurement tool. Hierarchical multiple regression analyses were performed to predict balance control using isokinetic knee strength performance for dominant and non-dominant legs. RESULTS: Final modelling included peak torque of hamstrings at 240°s-1 and peak torque of the quadriceps at 240°s-1 for the non-dominant leg (R 2 = 19.6%; p ≤ 0.001) and only peak hamstring torque at 240°s-1 for the dominant leg (R 2 = 11.3%; p = 0.003) as significant predictors of balance score. CONCLUSION: Findings indicate that balance control is widely influenced by peak hamstring torque and peak quadriceps torque at high angular velocity particularly in the non-dominant leg i.e., the supporting leg in soccer players.

Relationship Between Explosive Strength Capacity of the Knee Muscles and Deceleration Performance in Female Professional Soccer Players.

The present study aimed to investigate the relationship between linear deceleration performance and explosive strength capacity of the knee muscles. Fourteen female professional soccer players completed the maximal sprint deceleration tests and knee flexor (KF) and knee extensor (KE) isokinetic concentric (240° and 60°.s-1) and eccentric contractions (30°.s-1). Linear deceleration performance was evaluated from horizontal breaking force (F H), power (P H), and impulse (I H) during a maximal linear deceleration. The peak torque (PT) of KF and KE, PT ratio between KF and KE (conventional and functional H/Q ratio), rate of torque development (RTD) for each muscle group, and RTD between KF and KE (RTD H/Q) were extracted from the isokinetic contractions. Pearson's correlation coefficients revealed that the eccentric (30°.s-1) and concentric (60°.s-1, 240°.s-1) KE peak torque, and the concentric KF peak torque (240°.s-1) were significantly correlated with FH, PH , and IH (-0.75

Influence of Fatigue on the Rapid Hamstring/Quadriceps Force Capacity in Soccer Players.

The objective of this study was to examine the effect of fatigue on maximal and rapid force capacities and muscular activation of the knee extensors and flexors. Seventeen professional soccer players volunteered to participate in this study. Peak torque (Tpeak) and rate of torque development (RTD) of knee flexor (90°. s-1, -30°. s-1) and extensor (90°. s-1) muscles were measured before and after fatigue (i.e., 30 maximal knee extension and flexion repetitions at 180°s-1) performed on an isokinetic dynamometer. Hamstring to quadriceps peak strength and RTD ratios were calculated. Besides, using surface EMG, the mean level of activation (RMSmean), Rate of EMG Rise (RER), and EMG Frequency-Time maps were measured on quadriceps and hamstring muscles. Following fatigue, Tpeak, RTD, RER declined significantly in the two muscle groups (all p < 0.05) without modification of RMSmean. No decrease in conventional and functional H/Q ratios was observed after fatigue except for a significant increase in the H ecc30/Q con180 ratios (1.03 ± 0.19 vs. 1.36 ± 0.33, p < 0.001). Besides, the RTD H/Q ratios decreased significantly after fatigue, and the statistical parametric mapping analysis (SPM) performed on the EMG/angle curves, and EMG Frequency-Time maps showed that fatigue strongly influenced the muscle activation during the first 100 ms of the movement, following the higher EMG frequency component shift toward the lower frequency component. Our results show that the reduction of RTD and RER during the first 100 ms of the contraction after fatigue exercise makes more sense than any H/Q ratio modification in understanding injury risk in soccer players.

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.

Rapid hamstrings to quadriceps ratio at long muscle lengths in professional football players with previous hamstring strain injury.

Hamstring strain injuries (HSI) are the most common injury in male professional football and are potentially a primary risk factor to re-injury. Although the isokinetic strength ratios have often been used to identify strength imbalances that can augment the risk of injury in football players, the rate of torque development hamstring to quadriceps ratio (RTD H/Q) has rarely been considered in previous reports. Furthermore, little consideration has been given to selective hamstring lengths (30° of knee flexion) and its influence on torque production. The aim of this study was to investigate the RTD H/Q at long hamstring lengths, conventional (concentric/concentric) and functional (eccentric/concentric) H/Q ratios in football players with and without previous HSI. Twenty-four professional male football players (12 and 12 without previous HSI) performed maximal voluntary isometric contractions at long hamstring lengths (knee and hip flexed at 30° and 85°, respectively) and isokinetic concentric and eccentric contractions at 180°.s-1 and 60°.s-1. Conventional and functional H/Q ratios based on peak torque throughout the entire isokinetic range of motion and at long hamstring lengths were calculated. The RTD H/Q was extracted at long hamstring lengths in incrementing time periods of 50 milliseconds (ms) from the onset of contraction (50-250 ms). No significant differences were found between groups in any H/Q ratios studied. However, small effects (d = 0.4) were found in previously injured hamstrings to lower RTD H/Q at 50 ms and flexor eccentric torque. Previous HSI group showed small to moderate (0.4 > d < 0.6) higher RTD H/Q in late time intervals (>100 ms).

Do the exercises performed with a theraband have an effect on knee muscle strength balances?

BACKGROUND: In the current literature, exercises performed using fitness equipment and body weight have been used in order to decrease the bilateral deficit (BLD) and increase the hamstring-quadriceps (H/Q) ratio. No studies have previously investigated the effect of therabands, which are both portable and practical to be used anywhere, in regard to the BLD and H/Q ratio. OBJECTIVES: The purpose of this study was to investigate the effect of several 10-week lower extremity exercises performed through therabands on the BLD and H/Q ratio. METHODS: Twenty-seven voluntary male soccer players participated in the study. The players were categorized into the control group (CG) (n= 14) and the theraband exercise group (TBG) (n= 13). Theraband exercises for the lower extremity were performed by the soccer players in the TBG for four days every week over a 10-week period. The dominant (D) and non-dominant (ND) leg concentric extension and flexion of the soccer players were determined through an isokinetic dynamometer at 30∘s-1 and 240∘s-1 angular velocities. The data were analyzed through SPSS 24. To determine the difference between the BLD, H/Q ratios, and pre- and post-test of peak torque (PT), the Wilcoxon test was employed. RESULTS: As a result of the analysis, it was found that the BLD for the TBG decreased, which was statistically significant (p< 0.05), whereas there were no statistically significant differences for the H/Q ratio for both the CG and TBG; the D and ND leg H/Q rate of the TBG at 240∘s-1 angular velocity increased in the post-test. CONCLUSIONS: It was found that the exercises performed with the theraband were extremely efficient at increasing the PT and decreasing the BLD.

Effects of Different Combinations of Concentric and Eccentric Resistance Training Programs on Traditional and Alternative Hamstrings-to-Quadriceps Ratios.

Resistance training is often recommended for combined increases in traditional and alternative hamstrings-to-quadriceps (H:Q) ratios in order to reduce knee strength imbalance and associated hamstrings and knee ligament injury risk. The aim of this study was to investigate the effect of different concentric and eccentric resistance training programs on traditional and alternative H:Q ratios. Forty male volunteers were assigned to one of 4 groups: concentric quadriceps and concentric hamstrings (CON/CON, n = 10), eccentric quadriceps and eccentric hamstrings (ECC/ECC, n = 10), concentric quadriceps and eccentric hamstrings (CON/ECC, n = 10), or no training (control (CNTRL), n = 10). Traditional conventional (CR) and functional (FR), alternative rate of torque development (RTD), muscle size (MS), and muscle activation (MA) H:Q ratios were measured before and after six weeks of unilateral nondominant knee extension-flexion resistance training performed on an isokinetic dynamometer. The ECC/ECC training significantly increased FR (pre = 0.75 ± 0.11; post = 0.85 ± 0.15), whereas the lack of training (CNTRL) decreased the RTD H:Q ratio (pre = 1.10 ± 0.67; post = 0.73 ± 0.33). There were no differences between groups for the other traditional and alternative ratios following resistance training protocols. These findings suggest eccentric exercise for quadriceps and hamstrings as the most beneficial training program for inducing increases in the traditional FR. However, different resistance training strategies may be needed to also elicit increases in the alternative RTD, MS, and MA H:Q ratios for fully restoring muscle balance and reducing potential hamstrings and knee ligament injury risk.

Bilateral and ipsilateral peak torque of quadriceps and hamstring muscles in elite judokas.

OBJECTIVE: To examine bilateral and ipsilateral peak torque values of quadriceps (Q) and hamstring (H) muscles in elite judokas. METHODS: 16 elite male judokas were tested in concentric isokinetic strength of the quadriceps (Q) and hamstrings (H) muscles at 60° and 180° sec-1. Variables comprised average peak torque and the traditional H/Q, Q/Q, H/H ratios. Asymmetries between legs and differences between isokinetic muscle strength ratios were examined using paired t-tests and Cohen's d. RESULTS: In right (Rs) and left (Ls) extremity peak torque values, no significant difference was found between 60° and 180° sec-1 angular velocities (p>0.05). In peak torque values between PLs and NPLs, significant difference was found only in extension (Ex) phase at 60° sec-1 angular velocity p=0.001). (Significance was identified between (Q/Q) and (H/H) muscle ratios at 60° sec-1 (p=0.029). No significant difference was found in ipsilateral strength ratios at 60° and 180° sec-1 angular velocity (p>0.05). CONCLUSIONS: The Ex knee strength of PLs was high, particularly at low angular velocities, leading to differences of bilateral asymmetry in the Q muscle group. Regarding ipsilateral strength ratios, there were no differences in the H and Q muscle groups at both angular velocities, indicating that both legs were similar in terms of ipsilateral asymmetry.

The impact of joint angle and movement velocity on sex differences in the functional hamstring/quadriceps ratio.

BACKGROUND: Females are two to eight times more likely to suffer a non-contact injury compared with males thus the purpose of this study was to explore the influence of joint angle and movement velocity on sex differences in the functional hamstring to quadriceps ratio (H/QFUNC). METHODS: Isokinetic concentric and eccentric torque were determined in 110 participants (55 males and 55 females) through a 90° range of movement at 60, 120, and 240°/s. Testing was performed with the hip flexed at 10°. The H/QFUNC was determined at three specific joint angles (15, 30 and 45° flexion) and where peak torque occurred for concentric knee extension. RESULTS: A significant interaction effect (P<0.01) for sex and joint angle was observed with women demonstrating a lower H/QFUNC than males, especially at more extended knee positions. A significant sex by velocity interaction (P<0.01) indicated a lower H/QFUNC in women as velocity increased. Significant main effects (P<0.01) indicated that irrespective of sex the H/QFUNC increased as the knee extends and velocity increases. CONCLUSION: Given the reduced H/QFUNC in females compared to males at more extended knee positions and faster velocities, this may contribute to the observed sex bias in reported injury rates.

Age-related effects on maximal and rapid hamstrings/quadriceps strength capacities and vertical jump power in young and older females.

BACKGROUND AND AIMS: Declines in hamstrings and quadriceps maximal and rapid strength are commonly reported as a consequence of aging; however, few studies have investigated the influence of age on maximal and rapid hamstrings to quadriceps (H/Q) strength ratios. This study aimed to examine the effects of age on leg extension and flexion maximal and rapid torque production, H/Q strength ratios, and muscle power in healthy, young and old females. METHODS: Fifteen young (21 ± 2 years) and 15 old (69 ± 7 years) females performed 3 isometric leg extension and flexion maximal voluntary contractions (MVCs), from which peak torque (PT), early (0-30 ms) and late (0-200 ms) phase rate of torque development (RTD), and PT and RTD H/Q strength ratios were extracted. Lower-body peak power output (P max) was assessed through a vertical jump test. RESULTS: P max, PT, and early (RTD30) and late (RTD200) RTD variables of the leg extensors and flexors were lower (P ≤ 0.048) and PT and RTD200 H/Q strength ratios were higher (P ≤ 0.030) in the old compared to the younger females; however, no difference was observed for RTD30 H/Q (P = 0.300). There were also significant negative relationships in the older (r = -0.616 and -0.522; P = 0.014 and 0.046) but not the younger (r = 0.295 and -0.109; P = 0.286 and 0.698) females between P max and RTD30 and RTD200 H/Q strength ratios. CONCLUSION: The higher RTD200 H/Q ratio for the older females may contribute to the muscle power deficits often observed in elderly populations. Practitioners may use these findings to help identify older adults with low muscle power capacities and possibly overall functional decline.

Lower-extremity isokinetic strength ratios of elite springboard and platform diving athletes.

OBJECTIVES: The purpose of the present study was to examine knee extensor and flexor muscle strength ratios of an elite group of diving athletes. METHODS: Sixteen divers (10 females and 6 males) from the Brazil national team were assessed for lower-body strength. They had participated in international competitions such as the 2016 Olympic Games and 2015 Pan American Games. The dynamic concentric torque of their knee flexor and extensor muscles were evaluated using a Biodex isokinetic dynamometer. Bilateral tests were performed at 60º s-1. Flexor to extensor (F/E) peak torque ratio and percentage bilateral difference (BD%) was also measured. RESULTS: The results revealed that elite diving athletes produced higher than usual reported in previous studies for relative knee extension torque (3.2 for females and 3.6 for males N∙m∙kg-1). However, they presented low levels of knee flexor torque (1.5 for females and 1.8 for males N∙m∙kg-1). These results are reflected in a low F/E ratio (0.39 to 0.49). Males presented a greater BD% in knee flexors when compared to females (12.4% vs 6.6%). CONCLUSION: Elite diving athletes demonstrated high knee extensor and low knee flexor strength. This partially explains their low F/E ratio, which might increase risk of knee injuries. Strength and conditioning programs should strive to correct knee strength imbalances in diving athletes where necessary.

Comparison of hamstring-to-quadriceps ratio between accelerating and decelerating sections during squat exercise.

[Purpose] The aim of this study was to compare hamstring-to-quadriceps ratio between the accelerating and decelerating sections for anterior cruciate ligament protection during squat exercise. [Subjects and Methods] Nine asymptomatic males were enrolled in this study. The hamstring (medial part) and quadriceps (rectus femoris) muscle activities during squat exercise were measured, and the squat exercises were classified into two sections (accelerating and decelerating) by using an accelerometer. [Results] The hamstring-to-quadriceps ratio was significantly higher in the decelerating section than in the accelerating section during the squat exercise. [Conclusion] Application of an increasing decelerating section strategy during the squat exercise can prevent damage in patients with a weakened anterior cruciate ligament due to sports activities.

Comparison of the hamstring/quadriceps ratio in females during squat exercise using various foot wedges.

[Purpose] This study compared the hamstring/quadriceps ratio in females during squat exercise using various foot wedges. [Subjects and Methods] Nine females participated in this study. Surface electrodes measurements were taken over the hamstring and quadriceps under 3 squat exercise conditions, and the hamstring/quadriceps ratio was calculated. [Results] The hamstring/quadriceps ratio was significantly increased during squat exercise in inclined wedge condition (7.4 ± 1.8), compared to the declined wedge condition (5.3 ± 2.2) and no wedge condition (6.4 ± 3.2). [Conclusion] This study suggests that squat exercise in the inclined wedge condition may be effective for increasing the hamstring/quadriceps ratio in females.

Changes in muscle strength in u19 soccer players during an annual training cycle.

The aim of the study was to investigate the seasonal variation in isokinetic strength of the knee flexors and extensors, and conventional (H/QCONV) and functional (H/QFUNC) hamstring to quadriceps strength ratios in highly trained adolescent soccer players. The players (n=11; age 17.8±0.3) were measured at the end of the competitive season (autumn), at the beginning and the end of pre-season (winter) and during the sixth week of a new competitive season. Isokinetic peak torque (concentric and eccentric) was measured at 60°·s-1 in a sitting position with the hip flexed at 100°. The testing range of motion was set from 10 - 90° of knee flexion. The players performed a set of five maximum repetitions for both the dominant and non-dominant leg. Statistically significant differences (p<0.001) between the four seasonal measurements were noted for peak torque of the dominant leg knee flexors in concentric muscle action only. A post hoc analysis revealed a statistically significant increase in peak torque from the 1st to the 4th measurement (p<0.001; d=0.692) and from the 2nd to the 4th (p<0.01; d=0.564). The differences in the changes of peak torque of the knee flexors and extensors depending on type of muscle action and tendencies found in the H/Q ratios throughout the annual training cycle indicate that strength assessment of the knee flexors and extensors and their balance throughout the annual training cycle could be beneficial for elite male adolescent soccer players both in terms of performance and risk of injury.

Isokinetic concentric quadriceps and hamstring strength variables from the NFL Scouting Combine are not predictive of hamstring injury in first-year professional football players.

BACKGROUND: There are conflicting reports regarding the association between isokinetic concentric quadriceps and hamstring strength deficits and ratios and risk for hamstring injuries in athletes. PURPOSE: To determine if isokinetic concentric Cybex data collected during the annual National Football League (NFL) Scouting Combine are predictive of hamstring injury in professional American football players during their first season. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: All 32 NFL teams identified players selected during the first 5 rounds of the NFL annual draft who had hamstring injuries during their first professional season. Of these, 164 players with 172 injuries also had Cybex data from the previous year's Combine. Analyses compared injured legs with contralateral uninjured legs and also injured players with uninjured controls using a database of Cybex data from all players who participated in the NFL Scouting Combine from 2006 to 2011. RESULTS: No Cybex strength variable differentiated the injured legs from the contralateral uninjured legs or injured players from uninjured controls, even after taking into account days lost from activity. Mean ± SD peak torque for the injured and contralateral uninjured sides was as follows: 315.7 ± 70.0 and 313.5 ± 68.3 N · m, respectively (P = .773, paired t test), for quadriceps and 203.0 ± 42.4 and 205.3 ± 42.5 N · m, respectively (P = .608, paired t test), for hamstrings. The sensitivity and specificity for the hamstrings-to-quadriceps ratio predicting hamstring injury were 0.513 (95% confidence interval, 0.419-0.607) and 0.524 (0.495-0.554), indicating that the hamstrings-to-quadriceps ratio was not a useful predictor of injury (calculation used the mean ± SD ratio for injured legs, 0.656 ± 0.133). Side-to-side peak torque differences were also not predictive of injury, with more than a 10% difference (plus or minus) occurring commonly in both injured and uninjured players for quadriceps (53% prevalence for both injured and uninjured) and hamstrings (injured, 41% prevalence; uninjured, 43% prevalence). CONCLUSION: Isokinetic strength data collected from collegiate players at the NFL Scouting Combine were not useful for predicting risk of hamstring injury in subsequent professional NFL competition. These data call into question commonly accepted assumptions about risk factors for hamstring injury, at least for elite collegiate American football players, when the temporal relationship between Cybex testing and actual injury is several months.

Comparison of different hamstrings training effect on hamstrings:quadriceps strength ratios / 体力科学

Hamstring muscles form a multi-articular muscle group that crosses the hip and knee joints. It has been said that the imbalance in the hamstrings:quadriceps strength ratio (H:Q ratio) due to weaker hamstring muscles results in an increased susceptibility to hamstring strains and anterior cruciate ligament injuries. Four different hamstrings trainings, Hip Lift (HL), Single-leg Deadlift (DL), Leg Curl (LC), and Nordic Hamstrings (NH), were conducted and compared in the effect on conventional H:Q ratio. After the training of two months, significant increase of hip extension torque and H:Q ratios in the hip joint were found in the DL group, and significant increase of knee flexion torque and H:Q ratios in the knee joint were found in the LC group (<i>P</i> < 0.05). As a conclusion, DL and LC training could be practical for hamstrings injury prevention.