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Objective:To investigate the lower limb muscle strength characteristics in amateur runners with patellofemoral pain(PFP). Method:Thirty PFP amateur runners(20 males and 10 females)were recruited as the knee pain group,and 30 matched non-injured amateur runners were recruited as the non-knee pain group.The hip abductor strength,quadriceps strength,hamstring strength,hamstring/quadriceps ratio,and bilateral limb symmetry index were col-lected for all participants.Independent sample t-tests were used to compare the differences between the groups. Result:The hip abductor strength and bilateral limb symmetry index,quadriceps strength and bilateral limb symmetry index of male PFP amateur runners were significantly lower than those of the non-knee pain group,while the hamstring/quadriceps ratio was significantly higher than that of the non-knee pain group.The hip ab-ductor strength and bilateral limb symmetry index of female PFP amateur runners were significantly lower than those of the non-knee pain group. Conclusion:PFP amateur runners exhibit different lower limb muscle strength characteristics compared to non-knee pain runners,and the lower limb strength characteristics of male and female PFP amateur runners are not consistent.Therefore,functional and gender differences should be considered in the clinical treatment and rehabilitation training of PFP.

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Background: Previous literature has postulated a relationship between greater hamstring stiffness and a higher risk of sustaining injury. Shear wave elastography (SWE) presents a relatively new means for non-invasive evaluation of soft tissue elasticity pre- and post- injury or intervention. Purpose: 1. To establish baseline hamstring stiffness measures for young competitive athletes and (2) determine effect of targeted neuromuscular training (TNMT) on shear wave stiffness of the hamstring. Study Design: Un-blinded, prospective, non-randomized, cohort study. Methods: Six-hundred forty-two lower extremities from 321 high school and collegiate basketball athletes (177 F: 139 M) were examined for hamstring stiffness prior to the start of their competitive basketball season. Teams were cluster assigned to either the control or intervention (TNMT) group. Subjects in the control group underwent regular season activities as directed, with no influence from the research team. For the TNMT group, the research team introduced a hamstring targeted dynamic warm-up program as an intervention focused on activating the hamstring musculature. Results: Collegiate status was significant to hamstring stiffness for both sexes (p ≤ 0.02), but hamstring stiffness did not correlate to age or sex (r2 ≤ 0.08). Intervention was a significant factor to hamstring stiffness when the hip was positioned in extension (p ≤ 0.01), but not in deeper flexion (p = 0.12). This effect was sex-specific as TNMT influenced hamstring stiffness in females (p = 0.03), but not in males (p ≥ 0.13). Control athletes suffered three HAM injuries; TNMT athletes suffered 0 hamstring injuries. Conclusion: Higher SWE measurements correlated with increased risk of injury, male sex, and collegiate athletics. TNMT intervention can lessen muscle stiffness which may reduce relate to injury incidence. Intervention effectiveness may be sex specific. Level of Evidence: II.

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BACKGROUND: Maximal isokinetic strength ratios of joint flexors and extensors are important parameters to indicate the level of muscular balance at the joint. Further, in combat sports athletes, upper and lower limb muscle strength is affected by the type of sport. Thus, this study aimed to examine the differences in maximal isokinetic strength of the flexors and extensors and the corresponding flexor-extensor strength ratios of the elbows and knees in combat sports athletes. METHOD: Forty male participants (age = 22.3 ± 2.5 years) from four different combat sports (amateur boxing, taekwondo, karate, and judo; n = 10 per sport) were tested for eccentric peak torque of the elbow/knee flexors (EF/KF) and concentric peak torque of the elbow/knee extensors (EE/KE) at three different angular velocities (60, 120, and 180°/s) on the dominant and non-dominant side using an isokinetic device. RESULTS: Analyses revealed significant, large-sized group × velocity × limb interactions for EF, EE, and EF-EE ratio, KF, KE, and KF-KE ratio (p ≤ 0.03; 0.91 ≤ d ≤ 1.75). Post-hoc analyses indicated that amateur boxers displayed the largest EE strength values on the non-dominant side at ≤ 120°/s and the dominant side at ≥ 120°/s (p < 0.03; 1.21 ≤ d ≤ 1.59). The largest EF-EE strength ratios were observed on amateur boxers' and judokas' non-dominant side at ≥ 120°/s (p < 0.04; 1.36 ≤ d ≤ 2.44). Further, we found lower KF-KE strength measures in karate (p < 0.04; 1.12 ≤ d ≤ 6.22) and judo athletes (p ≤ 0.03; 1.60 ≤ d ≤ 5.31) particularly on the non-dominant side. CONCLUSIONS: The present findings indicated combat sport-specific differences in maximal isokinetic strength measures of EF, EE, KF, and KE particularly in favor of amateur boxers on the non-dominant side. TRIAL REGISTRATION: This study does not report results related to health care interventions using human participants and therefore it was not prospectively registered.

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Little attention has been paid to knee muscle strength after ACL rupture and its effect on prognostic outcomes and treatment decisions. We studied hamstrings (H) and quadriceps (Q) strength correlation with a patient-reported outcome measures score (International Knee Documentation Committee, IKDC), anterior tibial translation (ATT), and time post-injury in 194 anterior cruciate ligament deficient patients (ACLD) who required surgery after a failed rehabilitation program (non-copers). The correlation between knee muscle strength and ATT was also studied in 53 non-injured controls. ACLD patients showed decreased knee muscle strength of both the injured and non-injured limbs. The median (interquartile range) values of the H/Q ratio were 0.61 (0.52-0.81) for patients' injured side and 0.65 (0.57-0.8) for the non-injured side (p = 0.010). The median H/Q ratio for the controls was 0.52 (0.45-0.66) on both knees (p < 0.001, compared with the non-injured side of patients). The H/Q, ATT, and time post-injury were not significantly correlated with the IKDC score. ATT was significantly correlated with the H/Q of the injured and non-injured knees of patients, but not in the knees of the controls. Quadriceps strength and H/Q ratio were significantly correlated with ATT for both limbs of the patients. IKDC score correlated significantly with the quadriceps and hamstrings strengths of the injured limb but not with the H/Q ratio, ATT or time passed after injury.

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Cite this article: Bone Joint Open 2020;1-11:706-708.

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The purpose of this pilot case study is to investigate the effects of Pilates training on hamstring/quadriceps ratio, trunk strength, shoulder strength, and body composition in adolescent baseball players. Eight adolescent baseball players, 15 years of age, participated in Pilates program (supervised training, 50 min per session for three times a week for 8 weeks) using reformer and Cadillac. The intensity of the program was progressively increased by applying beginner level for 1-2 weeks, intermediate level for 3-6 weeks, and advance level for 7-8 weeks. To verify the effect of the Pilates program on hamstring/quadriceps ratio, trunk strength, shoulder strength and body composition, participants performed bioelectrical impedance analysis and isokinetic testing at pre- and posttraining. After the Pilates training, there were significant increases in body weight (P<0.01), left arm muscle mass (P<0.01), and trunk muscle mass (P<0.01). In addition, there were significant increases in left and right knee flexion peak torque (P<0.01 and P<0.05, respectively), right knee extension peak torque (P<0.05), left and right hamstring/quadriceps ratio (both P<0.01), trunk flexion peak torque (P<0.05) and shoulder flexion peak torque (P<0.05) after 8 weeks of training. Therefore, Pilates training increased muscle mass, hamstring/quadriceps ratio, trunk and shoulder strength, suggesting that it may help baseball players do better performance and prevent future injuries in adolescent players.

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The aim of this study was to examine the effects of 8 weeks of plyometric training on the ability to change direction and postural control in female basketball players. 25 national level female basketball players aged 18-27 years participated in the study. Volunteers were randomly assigned to an experimental group (n = 13) who replaced a part of their standard regimen by plyometric training twice weekly for 8 weeks, and a control group (n = 12) who continued their usual in-season training program. Before and after the intervention, the ability to change direction and postural control were assessed by force platform under both static and dynamic conditions (with the eyes open and then closed). Isokinetic testing was also performed to calculate the Hamstring/Quadriceps (H/Q) strength ratio. The intervention improved ability to change direction (p ≤ 0.001, d = 1.51) and shortened path length (p = 0.038, d = 0.937) during static balance testing. However, it did not yield significant inter-group differences in postural control in the antero-posterior plane. The stance in the medio-lateral plane seemed the most responsive to the intervention, with reductions in surface area (p = 0.012, d = 0.285), velocity with the eyes closed (p = 0.031, d = 0.968), and path length with the eyes open (p = 0.029, d = 0.968). The intervention did not change the H/Q ratio at the two speeds tested (60° and 120°.s-1). In summary, the addition of 8 weeks plyometric training to the usual in-season basketball regimen of top-level female basketball players enhanced their ability to change direction and reduced the risk of falls and injuries by improving postural control, but did not increase the H/Q measure of knee stability.

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PURPOSE: The purpose of this study was to investigate the isokinetic, eccentric and isometric hamstring/quadriceps (HQ) ratios in patients before and after ACL reconstruction (ACLR) using bone-patellar tendon grafts and to establish the relationships between HQ ratio and knee function. METHODS: Forty-four patients (mean age of 26.6 years) underwent isokinetic testing of quadriceps and hamstring muscles before and after ACLR and HQ ratios were calculated. Lysholm, IKDC and Cincinnati Scores were used to assess function. Isokinetic concentric and eccentric peak torque (Nm/kg) was measured at three different speeds: 60, 120, and 180°/s. Isometric strength was tested at 30° and 60° of knee flexion. RESULTS: For the isometric tests, the HQ ratio between the involved and non-involved limb was not different for the ACLD knee (p = 0.28) at 30° knee flexion, but significant at the 60° flexion angle (p = 0.02) and for the ACLR knees at 30° and 60° (p = 0.02). For the isokinetic tests, the ratio between involved and non-involved limb was significant for ACL-deficient knees at both 60 (p = 0.039) and 120°/s (p = 0.05). There were significant differences between limbs for all speeds in ACLR knees (p = 0.0003-0.01). For the eccentric tests, the HQ ratio between the involved and non-involved limbs was not significant for both the ACLD (p = 0.19) and ACLR knees (p = 0.29) at the speed of 60°/s. At 120 and 180°/s, there were significant differences between limbs for both the ACLD (p = 0.02) and ACLR knees (p = 0.003). Linear regression did not reveal significant relationships between Cincinnati, Lysholm, and IKDC scores and HQ ratios in the ACLD (R2 = 0.35, p = 0.58; R2 = 0.34, p = 0.63; R2 = 0.38, p = 0.49). In contrast, there were significant correlations between the Lysholm and IKDC scores and HQ ratios in the ACLR knees (R2 = 0.84, p = 0.002; R2 = 0.86, p = 0.001). CONCLUSIONS: The findings of this study suggest that the HQ ratio in ACLD patients was not a predictor, but an indicator of patient-perceived knee function following ACLR. LEVEL OF EVIDENCE: Level IV, case series.

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[Purpose] To assess the effect of hamstring and quadriceps strengthening exercises on pain intensity, gait velocity, maximum isometric strength, and activities of daily living of patients with knee osteoarthritis (OA). [Subjects and Methods] A total of 20 patients with knee OA, 50 to 65 years of age (57.65 ± 4.78 years), received hot packs, strengthening exercises for the quadriceps and the hamstring muscles and stretching exercises for hamstring muscles. Outcome measures included: the Western Ontario and McMaster Universities OA index questionnaire (WOMAC) scores for assessing health status and health outcomes of knee OA; self-reported pain intensity scores, measured using a visual analogue scale; the 50 ft walk test (a measure of gait velocity and function); and handheld dynamometry (a tool used to measure maximum isometric strength of knee extension and flexion). [Results] There was a significant difference between pre- and post-intervention measures of pain intensity, 50 ft walk times, hamstring strength, and quadriceps strength. Significant differences in WOMAC measures were also observed in the subscales of pain, stiffness and physical function, as well as WOMAC total scores. [Conclusion] Strengthening the hamstring muscles in addition to strengthening the quadriceps muscles proved to be beneficial for perceived knee pain, range of motion, and decreasing the limitation of functional performance of patients with knee OA.

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The purpose of this study was to investigate of isokinetic strength of quadriceps and hamstring, hamstrings/quadriceps ration in elite sports athletes to provide the data for injury prevention, fitness level evaluation and training methodology. The subjects selected for this study were 104 elite sports athletes. They didn't have any medical problem. Isokinetic peak torque, flexor/extensor ratio at 60 deg/sec of the knee extension and flexion were measured using an cybex 770. The data were analyzed utilizing One way ANOVA. The level of statistical significance was set at p<.05. On the basis of the results analyzed in this study, conclusion were drawn as follow: 1. Dominant knee extension peak torque (Nm) were no significant differences in man but man elite athletes were higher than woman elite players in 60 deg/sec (p<.05). 2. Dominant knee extension peak torque (% body weight) of man elite athletes were higher than woman elite players in 60 deg/sec except only man volleyball athletes (p<.05). 3. Dominant knee flexion peak torque (Nm) were no significant differences in man but man elite athletes were higher than woman elite players in 60 deg/sec (p<.05). 4. Dominant knee flexion peak torque (% body weight) of man elite athletes were higher than woman elite players in 60 deg/sec (p<.05). 5. Knee flexion/extension peak torque ratio (H : Q) were no significant differences according to sex and proper H : Q ratio was 54~64%.

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OBJECTIVE: We tested peak torques of knee extensors and knee flexors using an isokinetic dynamometer (Cybex model 770) in middle-aged and aged populations, and calculated functional hamstring: quadriceps ratios (H/Q ratios) and conventional hamstring: quadriceps ratios. We present the normative data of these parameters in decade age groups for both sexes. METHOD: Using an isokinetic dynamometer we determined the peak torques of knee extensors and knee flexors at angular velocities of 30, 60 and 180 degrees/sec in normal people (120 males, 154 females in the age range 31 to 70 years) and using these peak torque values to calculate functional H/Q ratios and conventional H/Q ratios. RESULTS: Normative data were presented. As age increased, the magnitudes of the peak torques of most knee flexors and knee extensors decreased, but conventional and functional H/Q ratios were not found to be significantly correlated with age in either sex. CONCLUSION: Normative data by decade age in both sexes were obtained. It is hoped that this data will be beneficial for the testing of knee joint function.

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