Isokinetic Strength Assessment Research Articles

Strength characteristics in faster change of direction basketball players: A comparison across cutting angles.

Change of directions (COD) involves multidirectional and complex actions, with performance influenced by multiple factors. As lower limb strength is one of the most determinant of COD performance, the present study aimed to (a) explore the differences in strength outcomes across different lower limb muscle actions between faster and slower basketball players in COD actions at different angles and (b) analyse the relationship between isometric, concentric and eccentric strength outcomes and COD performance at different cutting angles. Twenty-five basketball players (44% female) completed a battery of tests, encompassing isokinetic and isometric squat strength assessments, along with COD tests at 45°, 90° and 180°. Players were categorised as 'low-performance' and 'high-performance' groups based on execution time in COD, facilitating a comparison between performance groups. Results indicated that concentric strength showed the greatest differences between performance groups at 45° COD (effect size≥0.813; p≤0.034). Isometric and eccentric strength demonstrated a moderate-to-large relationship with 90° COD performance (Rho≥0.394; p≤0.045), and all muscle actions exhibited a large relationship with 180° COD (Rho≥0.445; p≤0.030). Moreover, the fastest players showed higher levels of concentric strength relative to eccentric strength, regardless of the cutting angle. These findings hold practical applications, suggesting that basketball coaches should train a specific kind of muscle action depending on the individual players' COD demands, focusing on improving the rapid eccentric force application while striving to reduce the eccentric/concentric ratio.

Does It Matter? Isometric or Isokinetic Assessment of Quadriceps Strength Symmetry 9 Months After ACLR in Collegiate Athletes.

Greater quadriceps strength symmetry is associated with better outcomes after anterior cruciate ligament reconstruction (ACLR). Isometric and isokinetic assessments of quadriceps strength inform therapeutic exercise prescription and return-to-sport decisions. It is unclear whether isometric and isokinetic measures provide similar information post-ACLR. Quadriceps strength symmetry is similar between isometric and isokinetic assessments. Isokinetic and isometric strength symmetries have similar associations to functional knee kinetics and self-reported knee function. Cross-sectional study. Level 3. NCAA Division I athletes (N = 35), 8.9 ± 2.5 months post-ACLR completed isometric and isokinetic quadriceps strength assessments, countermovement jumps (CMJs), and treadmill running. Self-reported knee function was assessed using the International Knee Documentation Committee Subjective Knee Form (IKDC). Agreement between isometric and isokinetic strength symmetry was assessed using Bland-Altman analysis, with associations to functional knee kinetics and IKDC assessed using Pearson correlations and linear regressions. Mean difference in quadriceps strength symmetry between isokinetic and isometric assessments was 1.0% (95% limits of agreement of -25.1% to 23.0%). Functional knee kinetics during running and CMJ were moderately to strongly associated with isometric strength symmetry (r = 0.64-0.80, P < 0.01) and moderately associated with isokinetic strength symmetry (r = 0.41-0.58, P < 0.01). IKDC scores were weakly to moderately associated with isometric (r = 0.39, P = 0.02) and isokinetic (r = 0.49, P < 0.01) strength symmetry. Isokinetic and isometric assessments of quadriceps strength symmetry in collegiate athletes 9 months post-ACLR demonstrated strong agreement. Quadriceps strength symmetry is associated with functional knee kinetic symmetry post-ACLR. Considerable individual variation suggests mode of contraction should be consistent throughout postoperative assessment. Isometric strength symmetry may be a better indicator of functional knee kinetic symmetry, while isokinetic strength symmetry may be associated more closely with patient-reported outcomes.

Assessment of Isokinetic Strength of Knee Extension/Flexion of Individuals With Intellectual Developmental Disabilities—Systematic Review With Protocol Proposal

ABSTRACT Muscle performance is a crucial determinant of physical function in the daily lives of individuals with intellectual developmental disabilities (IDD), with lower strength levels often leading to loss of independence. The isokinetic dynamometer has been established as a reliable method for assessing muscle performance in this population. This article outlines the design of a protocol to be adopted to assess isokinetic knee strength in individuals with IDD. Using systematic review methodology, electronic searches were conducted in PubMed, Scopus, SPORTDiscus, and Web of Science databases, including articles published between January 1990 and September 2022. The key terms were combined with the Boolean operator “AND” or “OR”. After the methodological process, 23 studies were included for analysis. The protocol proposal consists of 8 phases, covering previous considerations: (a) warm-up, (b) familiarization; (c) equipment adjustment, choosing the limb to evaluate and in what type of action (concentric and/or eccentric); (d) number of repetitions and sets; (e) the rest duration; (f) angular velocity to be tested; and (g) parameters for analysis. It is intended that this article provide insights into the development of a useful tool for the various stakeholders interested in assessing the isokinetic knee strength of individuals with IDD.

No Association Between Injury-Related Fear and Isokinetic Quadriceps Strength in Individuals With a History of Anterior Cruciate Ligament Reconstruction.

Injury-related fear and quadriceps strength are independently associated with secondary anterior cruciate ligament (ACL) injury risk. It is not known whether injury-related fear and quadriceps strength are associated, despite their individual predictive capabilities of secondary ACL injury. The purpose of this study was to examine the association between injury-related fear and quadriceps strength in individuals at least 1year after ACL reconstruction (ACLR). Cross-sectional study. Forty participants between the ages of 18 and 35years at least 1year post unilateral primary ACLR. Participants completed the Tampa Scale of Kinesiophobia-11 (TSK-11) and a standard isokinetic quadriceps strength assessment using the Biodex Isokinetic Dynamometer. Pearson Product-Moment correlations were used to examine the linear association between the TSK-11 scores and peak torque (in nanometers per kilogram) for each limb and between the TSK-11 scores and limb symmetry indices for each limb. Pearson Product-Moment correlation coefficients (r) were interpreted as very high (.90-1.00), high (.70-.90), moderate (.50-.70), low (.30-.50), and no correlation (.00-.30). The average TSK-11 score was 18.2 (5.3), average ACLR peak quadriceps torque was 1.9 (0.50)N·m/kg, average contralateral peak quadriceps torque was 2.3 (0.48)N·m/kg, and average limb symmetry index was 85.3% (12.6%). There was no statistically significant correlation between the TSK-11 and peak quadriceps torque on the ACLR limb (r = .12, P = .46), the TSK-11 and contralateral limb (r = .29, P = .07), or the TSK-11 and limb symmetry index (r = -.18, P = .27). There was no association between kinesiophobia and peak isokinetic quadriceps strength in individuals at least 1year post-ACLR. Both factors, independently, have been shown to influence risk of secondary injury in patients after ACLR.

Assessment of Isokinetic Trunk Muscle Strength and Fatigue Rate in Individuals after Bariatric Surgery.

Background and Objectives: Lean body mass loss after bariatric surgery (BS) is remarkable, despite an effective long-term mass reduction and significant declines in comorbidities. A person's functional capacity is adversely affected when their skeletal muscle strength declines by up to 30%. This study aimed to assess the isokinetic trunk muscle strength and fatigue rate in individuals after BS. Materials and Methods: This study included fifty-eight patients, both male and female, ranging in age from 19 to 45. Twenty-seven individuals had BS and twenty-seven healthy people served as the control group. The primary outcomes were the measurement of the concentric and eccentric isokinetic muscle strength of the trunk flexor and extensor muscles. An isokinetic dynamometer (Biodex Rehabilitation and Testing System 3) was used for the assessment of the isokinetic muscle strength. Noraxon EMG was used to determine a secondary outcome, which was the median frequency slop (MF/time) and root mean square slop (RMS/time) of the lumbar erector spinea muscle at 50% of the Maximum Voluntary Isometric Contraction (MVIC). Outcome measures were assessed for both groups. Results: Compared to the control group, the bariatric group showed a lower mean value of both concentric and eccentric isokinetic muscle strength for the flexor and extensor trunk muscles (p < 0.05). In terms of the EMG fatigue rate, the RMS slope increased significantly more than that of the control group, while the MF slope decreased (p > 0.05). Conclusions: The current study found that, in comparison to the healthy subjects, the BS group showed reduced levels of fatigue and isokinetic strength in the trunk muscles. Based on these results, it is recommended that individuals who underwent BS take part in tailored rehabilitation programs to avoid potential musculoskeletal issues in the future.

Resistance Exercise Program Is Feasible and Effective in Improving Functional Strength in Post-COVID Survivors.

Background: Evidence suggests that COVID-19 infection can cause lasting health consequences. Multidisciplinary rehabilitation services have been recommended to reduce the sequalae. However, the effectiveness of physical exercise interventions remains insufficiently documented. The aim of this study was to develop and implement a specific and well-tolerated protocol-based intervention to reduce muscle weakness in older adults impacted by COVID-19. Methods: Forty-six older adults were randomized into intervention and control groups. Isometric and isokinetic strength assessments were conducted for selected muscle groups using a JBA Staniak® torquemeter and Biodex System 3 dynamometer. Functional abilities were evaluated with the Time Up and Go test and Chair Stand Tests. Results: Men in the intervention group demonstrated a significant improvement in static conditions for knee flexors (KFs), trunk extensors (TEs) and trunk flexors (TFs) and in dynamic conditions for knee extensors (KEs). Women in the intervention group showed a significant improvement in static conditions for EFs, KFs, TEs and TFs and in dynamic conditions for a KE and a KF. The interaction GROUP × TESTING SESSION was significant for the Chair Test (s) and Chair Test (n). Conclusions: Our results demonstrate the effectiveness of a well-tolerated, protocol-based approach that can be used to diminish long-lasting functional deficits in post-COVID survivors.

Lower limbs strength variations between injured and non-injured professional soccer players.

Due to its physical demands, professional soccer is becoming a real challenge regarding players' exposure to high injury risk. Given its tight correlation with high-intensity actions, muscular strength is a crucial physical characteristic for soccer players. Therefore, the aims of this study are (a) to compare the vertical jumping performance during the season according to the injury profile, and (b) to investigate differences in isokinetic strength performance at the beginning and the end of the season. Twenty-one male professional soccer players (age: 26.0 ± 4.1 years, height: 181.0 ± 6.9 cm, body mass: 73.7 ± 6.9 kg) were assessed in isokinetic strength (Biodex System 4 Pro Dynamometer), and Optojump Next (Microgate, Bolzano, Italy). Isokinetic strength analyses considered the peak torque scores of knee flexors and knee extensors, according to the player's preferred and non-preferred limb. The countermovement and squat jump maximum height were assessed as lower body explosive strength indicators. No significant differences were found when comparing injured and non-injured players in vertical jump and isokinetic strength assessments. However, significant results were found when comparing both groups' initial and final evaluation in isokinetic strength assessment, with both groups significantly improving their performance. Our findings indicate that the overall lower body strength performance was not a discriminant factor between injured and non-injury players. Thus, muscular strength assessment performance increased throughout the season independently of the injury profile. Future research needs to integrate other variables related to sports injuries since they seem to result from multifactorial causes.

Reliability and validity of new isokinetic strength assessment for rotator cuff muscles in a muscle architecture-based position.

Isokinetic strength assessment of the rotator cuff muscle is frequently applied in a variety of shoulder postures, but none of these consider muscular architecture, which is one of the most important aspects of improving strength development. This study aimed to examine the test and retest reliability and validity of the muscle architecture-based position (MABP), which is 25° abduction and 20° external rotation, in healthy subjects to be able to select a better isokinetic assessment position for shoulder rotator cuff muscles. A total of 54 healthy males with a mean age of 21.0 ± 1.2 years and mean body mass index of 22.8 ± 1.7 kg/m2 completed an isokinetic measurement session. All of the tests were performed on an IsoMed 2000 isokinetic dynamometer concentrically and eccentrically for both upper limbs at 60°/s angular velocity. All of the participants completed 3 measurement sessions: the first represented the isokinetic testing and was performed in the scapular neutral position (SNP) (45° shoulder flexion and abduction), the second represented the MABP (25° abduction and 20° ER) for shoulder rotator cuff muscles, and the third represented the test and retest of the MABP. The correlations between the 2 techniques for assessing concurrent validity ranged from 0.908 to 0.994. The values obtained from the MABP were higher than those obtained in the SNP. There was no systematic bias for any measurements between the MABP and the retest of the MABP (p > 0.05). The intraclass correlation coefficients representing the test and retest reliability results for each variable measured with the MABP was higher than 0.98 and this value was considered as excellent reliability. In conclusion, the MABP can be used to assess the isokinetic strength of the rotator cuff muscles safely and confidently, with increased quantities of force being released and measurement at optimal muscle tension.

Which Tests Predict 6-Month Isokinetic Quadriceps Strength After ACL Reconstruction? An Examination of Isometric Quadriceps Strength and Functional Tests at 3 Months.

Restoration of quadriceps strength after anterior ligament reconstruction (ACLR) is a persistent challenge for patients and clinicians. Inadequate recovery of quadriceps strength has been linked to increase risk of re-injury. Developing methods of early identification of strength deficits is essential to allow clinicians to provide more individualized interventions early in the rehabilitation process. To determine whether 3-month isometric quadriceps strength, the Y-Balance Test (YBT), and the anterior step-down test are predictive of isokinetic quadriceps strength at six months in adolescents after ACLR. Retrospective cohort. Thirty-six adolescent patients with primary ACLR (58% female, 36% with concomitant meniscal repair, age: 15.7 ± 1.6 years). At three months post-operative, isometric quadriceps strength via isokinetic dynamometer, YBT-Lower Quarter, and anterior step-down tests were completed. At six months post-operative, an isokinetic knee strength assessment was completed. Regression analysis was used to evaluate the predictive relationship between 3-month isometric tests and 6-month isokinetic knee extension tests. Three-month post operative isometric quadriceps peak torque predicted isokinetic quadriceps peak torque at 6 months, F(1,34) = 19.61, p <0.001. Three-month isometric quadriceps peak torque accounted for 36.6% of the variance in normalized isokinetic quadriceps peak torque at 6 months with adjusted R2 = 34.7%. Including YBT anterior reach (β = 0.157, p = 0.318) in regression added 1.9% of variance when predicting 6-month isokinetic quadriceps peak torque, F (2,33) = 10.32, p <0.001, R2 = 0.385, ΔR2 = 0.019. At three months post-ACLR, isometric strength testing appears more optimal than other functional tests in predicting isokinetic quadriceps peak torque in later stages of rehabilitation for adolescents. Clinicians should use tests at three months that measure quadriceps strength if aiming to predict isokinetic quadriceps peak torque at six months post-ACLR, rather than using functional tests such as the YBT-LQ or anterior step-down. Level 3.

Assessment of isokinetic hip muscle strength and predictors in patients with lower limb amputation: A cross-sectional study.

The purpose of the study was to determine isokinetic features and analyze significant predictors related to activity level of patients with lower limb amputation. Forty-three male patients (mean age: 32.9±8.8 years; range, 21 to 50 years) with lower limb amputation were recruited consecutively for this cross-sectional study between March 1, 2022, and June 30, 2022. The hip flexor and extensor peak torques and total work were evaluated by an isokinetic dynamometer. The secondary outcome measure was the Amputee Mobility Predictor. A linear regression analysis was used to determine factors independently affecting Amputee Mobility Predictor scores. All data of patients with unilateral amputation, except for flexor (p=0.285) and extensor (p=0.247) peak torques on the dominant side, were higher than those of patients with amputation. Dominant side extensor peak torque was statistically higher than nondominant side extensor peak torque (59.4±30.7 vs. 43.4±32.0) in patients with bilateral amputation. No difference was detected between amputated and intact sides of patients with unilateral amputation. Both flexor and extensor total work on the amputated side of the patients with below-knee amputation were higher than the patients with above-knee amputations (63.5±21.1 vs. 94.1±34.3 and 67.1±34.0 vs. 113.0±51.5, respectively). Unilateral amputation (odds ratio: 7.442) and nondominant side extensor total work (odds ratio: 0.615) were found to be significant predictors related with amputee mobility predictor scale. It is possible to have an idea about the possible activity level of the patients with lower limb amputation with the help of the predictors obtained in the current study.

Bilateral Asymmetry and the Relationship Between Unilateral Isokinetic Strength and Balance Performance in Male Adolescent Football Players

Muscle strength and balance ability have been related to injury prevention and game actions performance in football. The aims of this study are twofold: (1) to examine bilateral asymmetries in isokinetic strength and balance assessments, and (2) to evaluate the relationship between muscle strength and balance measures. Eighty-eight male adolescent football players were assessed for body composition (InBody 770), isokinetic strength (Biodex System 4 Pro Dynamometer), and balance performance (Biodex Balance System). Paired samples t-tests were conducted to determine bilateral differences in strength and balance. Pearson correlations and multiple linear regression analyses evaluated the relationship between strength and balance. No significant bilateral strength differences were observed in knee flexors (KF) and knee extensors (KE) peak torque (PT) scores. No bilateral differences were found for balance measures, except in the lateromedial stability index, which was better while performing with the preferred leg (p ≤ 0.01; d = 0.29). Significant correlations were found between KE PT and balance tasks (p ≤ 0.01). KF and KE PT shared between 18 and 22% of the common variance in the overall stability index in the non-preferred and preferred leg, respectively. Monitoring strategies of bilateral asymmetries may be crucial to enhance performance in tasks underpinned by unilateral movements, such as changes of direction and sprints, and to identify players at risk of injury. Adopting these strategies during the early stages of football training might be crucial for players’ long-term development.

Post-Operative Modified All-Inside ACL Reconstruction Technique's Clinical Outcomes and Isokinetic Strength Assessments.

Anterior cruciate ligament (ACL) injuries are very common among the athletic population. ACL reconstruction (ACLR) performed because of these injuries is one of the procedures performed by orthopedic surgeons using different grafting methods. This study aims to compare the data related to post-operative 6-month isokinetic strength values, strength-related asymmetry rates, time parameters, and joint angle in athletes who underwent ACLR with the Modified All-inside (4ST) technique, on both the healthy knee (HK) and the ACLR-applied sides. A total of 20 athletes from various sports on whom the 4ST ACLR technique had been applied by the same surgeon were evaluated retrospectively. Lysholm, Tegner, and International Knee Documentation Committee (IKDC) scores of the patients were obtained pre-operative and at 6 months post-operative. Isokinetic knee extension (Ex) and flexion (Flx) strengths on the HK and ACLR sides of the patients were evaluated with a series of four different angular velocities (60, 180, 240, and 300°/s). In addition to peak torque (PT) and hamstring/quadriceps ratio (H/Q) parameters, the findings were also evaluated with additional parameters such as joint angle at peak torque (JAPT), time to peak torque (TPT), reciprocal delay (RD), and endurance ratio (ER). There was a significant improvement in the mean Lysholm, Tegner, and IKDC scores after surgery compared with pre-operative levels (p < 0.05). As for PT values, there were significant differences in favor of the HK in the 60, 180, and 300°/s Ex phases (p < 0.05). In terms of the H/Q and (hamstring/hamstring)/(quadriceps/quadriceps) (HH/QQ) ratios, there were significant differences at 300°/s (p < 0.05). In terms of JAPT, there were significant differences in the 300°/s Ex and 180°/s Flx phases (p < 0.05). In terms of TPT, there were significant differences in the 300°/s Ex phase (p < 0.05). In terms of RD and ER, no significant difference was observed between the HK and ACLR sides at any angular velocity. Although differences were observed in PT values, particularly in the Ex phase, this did not cause a significant change in H/Q ratios. Similar results were observed for additional parameters such as JAPT, TPT, RD, and ER. The results show that this ACLR technique can be used in athletes in view of strength gain and a return to sports.

The Influence of Isokinetic Trunk Flexor and Extensor Strength on Dynamic Balance in Children

This study assessed whether trunk flexor and extensor strength were predictors of time to stability (TTS) and center of pressure (CoP) during hop and hold tasks in children. Seventeen boys (age, 10.1 ± 1.6 years; height, 1.45 ± 0.11 m; mass, 26.7 ± 7.83 kg) undertook isokinetic strength assessments of concentric and eccentric trunk flexors/extensors at 60°/s, and anterior/medial hop tasks. Hierarchical multiple regressions determined whether concentric and eccentric trunk flexor/extensor peak torques predict TTS using a composite score (CompX CompY CompZ) and CoPX and CoPY. Concentric trunk flexors were the strongest predictor for TTS CompXY, with concentric flexion and eccentric extension predicting TTS CompY. All muscle actions were also strong predictors for CoPY during hop tasks. These findings have implications for the assessment of trunk musculature strength and measures of postural control within a young healthy population. The development of trunk musculature strength may aid improvements in dynamic balance tasks in children, with implications for fall and injury risk. To improve trunk musculature strength and the potential to maintain postural control, a combination of concentric and eccentric exercises with other training modalities appears relevant due to the increased relevance to the demands of balance maintenance.

Isokinetic strength assessment of trunk muscle and its relationship with spinal-pelvic parameters in patients with degenerative spinal deformity.

The incidence rate of degenerative spinal deformity (DSD) has gradually increased in the elderly. Currently, the relationship between the functional status of trunk muscle and the spinal-pelvic parameters of DSD patients remains unclear. This paper aims to explore the relationship between the two factors and provide new clues for exploring the mechanism of the occurrence and development of DSD. A total of 41 DSD patients treated in our hospital (DSD group) and 35 healthy volunteers (control group) were selected. Muscle strength was evaluated using an IsoMed-2000 isokinetic dynamometer, and the trunk flexor and extensor peak torque (PT) of subjects was measured at a low, medium, and high angular velocity of 30∘/s, 60∘/s, and 120∘/s, respectively. Hand grip strength (HGS) was assessed using an electronic grip dynamometer and Surgimap software was used to measure the spinal-pelvic parameters, including the sagittal vertical axis (SVA), thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence rate (PI), and PI-LL, and the relationship between trunk muscle function and various parameters was analyzed. Under the three angular velocities, the flexor and extensor PT values in the DSD group were lower than those in the control group, and only the extensor PT showed a statistically significant difference (P< 0.05). There was no significant difference in HGS between the two groups (P> 0.05). In the DSD group, the extensor PT at 30∘/s was significantly negatively correlated with SVA (P< 0.05). At 60∘/s and 120∘/s, the extensor PT was significantly negatively correlated with SVA and PT (P< 0.05). Trunk extensor strength is significantly lower in DSD patients than in normal controls. The decline in trunk extensor strength in DSD patients is a type of local muscle dysfunction more closely related to the deformity, which is likely involved in the compensatory mechanism of DSD and may reflect the overall imbalance of the trunk.

Age-, Sex-, and Graft-Specific Reference Values From 783 Adolescent Patients at 5 to 7 Months After ACL Reconstruction: IKDC, Pedi-IKDC, KOOS, ACL-RSI, Single-Leg Hop, and Thigh Strength.

OBJECTIVE: To describe age-, sex-, and graft source-specific reference values for patient-reported, physical function, and strength outcome measures in adolescents at 5 to 7 months after anterior cruciate ligament reconstruction. DESIGN: Cross-sectional study. METHODS: Data were collected at 3 universities and 2 children's hospitals. The participants completed at least one of the International Knee Documentation Committee (IKDC) Subjective Evaluation Form, Pediatric IKDC (Pedi-IKDC), Knee Injury and Osteoarthritis Outcomes Score (KOOS), and Anterior Cruciate Ligament Return to Sport After Injury (ACL-RSI) Scale. Participants also completed single-leg hop tests and/or isokinetic quadriceps and hamstrings strength assessments (at 60°/s). Reference values were summarized using descriptive statistics and stratified for age, sex, and graft source. RESULTS: Reference values were reported for common patient-reported outcomes and measures of physical function and strength from 783 participants (56% females, age = 16. 4 ± 2.0 years) who were in early adolescence (12-14 years, N = 183, 52% females), middle adolescence (15-17 years, N = 456, 58% females), or late adolescence (18-20 years, N = 144, 55% females). Three hundred seventy-nine participants (48.4%) received a bone-patellar tendon-bone autograft, 292 participants (37.3%) received hamstring tendon autograft, and 112 participants (14.3%) received autograft or allograft from an alternative source. CONCLUSION: Reference values for common patient-reported outcomes and measures of physical function and strength differed depending on a patient's age, sex, and graft source. Using patient-specific reference values, in addition to previously described age-appropriate cutoff values, may help clinicians monitor and progress patients through rehabilitation and return to physical activity after anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther 2023;53(4):1-8. Epub: 23 January 2023. doi:10.2519/jospt.2023.11389.

Effects of sprint versus strength training on risk factors for hamstring injury in football players.

This study aimed to compare the effects of in-season sprint training vs. Nordic hamstring exercise (NHE) training on risk factors for hamstring strain injuries (HSI). Eighteen male university football players (20.9±2.5 years; 181±7 cm; 75.8±9.1 kg; 15.2±3.5% of body fat) were randomly allocated to a sprint group or NHE group. They completed baseline isokinetic strength and sprint mechanics assessments prior to their assigned intervention performed twice weekly for 4-weeks, before post-testing. A mixed design ANOVA with repeated measures assessed time, group and interaction effects for all risk factors. There were significant increases in hamstring eccentric peak torque at 60°·s-1 (+8% - 9.9%), the torque produced at 20° (+15%) and 10° (+21% - 31%), as well as a rightward shift in angle of peak torque towards knee extension (-27% - -36%) in both groups (P<0.05). We also observed a significant increase (+24.5%) in hamstring eccentric peak torque at 180°·s-1 in the strength group only and significant improvements (+29.4%) in the rate of torque development of the dominant leg at 60°·s-1 in the sprint group only (P<0.05). No significant effect was noted on sprint performance or sprint mechanics (P>0.05). These findings suggest that both training programs can be effective to mitigate the risk of HSI, but through different mechanisms.

Predictors of linear sprint performance in professional football players.

The purpose of this study was to analyze the relationship between sprint performance (time), and strength and power capabilities in football players. A total of 33 professional Portuguese football players performed isokinetic strength assessments, countermovement jumps (CMJ), squat jumps (SJ), and 10, 20 and 30 m sprints. Pearson's correlation (r) was used to determine the relationships between variables. Concentric knee extensor torque at 180° · s-1 was largely-to-very largely correlated with 10 m (r = -0.726), 20 m (-0.657) and 30 m sprints (r = -0.823). Moderate inverse correlation were observed between CMJ (r = -0.425 and r = -0.405) and SJ height (r = -0.417 and r = -0.430), and 20 m and 30 m sprint performance, respectively. Multiple linear regression combining KEcon 180° · s-1 and KFcon 180° · s-1 demonstrated that the model was significant for predicting 10 m sprint time (F (2, 8) = 5.886; R 2 = 0.595). The model combining SJ, CMJ and KEcon 180° · s-1 was also significant for predicting 20 and 30 m sprint times (F (3, 7) = 2.475; R 2 = 0.515 and F (3, 7) = 5.282; R 2 = 0.562; respectively). In conclusion, peak torque at higher velocities and vertical jump performance correlates significantly with linear sprint performance (time). For practitioners seeking to improve linear sprint performance in football players, evaluation of high speed strength and vertical jump indices should be undertaken.

Pre- and Post-Operative Hamstring Autograft ACL Reconstruction Isokinetic Knee Strength Assessments of Recreational Athletes.

Background and Objectives: Anterior cruciate ligament (ACL) injuries are common injuries with a high incidence among people with high physical activity levels. Therefore, ACL reconstruction (ACLR) is one of the most common surgical procedures performed in sports medicine. This study aims to compare the pre- and 6-month post-operative isokinetic knee strengths in healthy (HK) and ACL knees of patients who underwent semitendinous/gracilis (ST/G) ACLR. Materials and Methods: A retrospective cohort of 21 recreational athletes who underwent ST/G ACLR by the same surgeon were evaluated. The pre- and 6-month post-operative isokinetic knee extension (Ex) and flexion (Flx) strengths of the HK and ACLR patients were evaluated in a series consisting of three different angular velocities (60, 180 and 240°/s). Of all the findings, peak torque (PT) and hamstring/quadriceps (H/Q) parameters were evaluated. Results: There was a significant improvement in post-operative Lysholm, Tegner and IKDC scores compared to pre-operative scores (p < 0.05). There were significant differences in pre-operative and post-operative knee Ex and Flx strengths at angular velocities of 60°, 180° and 240°/s in both the ACLR and HK groups (p < 0.001). There was no significance at 240°/s Flx for ACLR (p > 0.05). As for H/Q ratios, there was a significant difference between pre- and post-operative values only at 60°/s angular velocity in both ACLR and HC (p < 0.005). Conclusions: The pre-operative and 6-month post-operative results of the ST/G ACLR showed that there was a high level of recovery, particularly in quadriceps strength, while the increase in strength was less in the hamstring. The significance observed at 60°/s in H/Q ratios was within normal ranges. It can be argued that the ST/G ACLR method is feasible for people with high physical activity levels and for athletes.

Shoulder Internal Rotator Strength as Risk Factor for Shoulder Pain in Volleyball Players.

The aim of this study was to identify the intrinsic factors that could increase risk of shoulder pain in adolescent volleyball players. Twenty-eight young male volleyball players (between 14 and 18 years old) participated in this study. Athletes were submitted to: isokinetic muscle strength assessment of shoulder rotator muscles, ball service speed assessment, anterior and posterior drawer test, apprehension test, groove sign and scapular dyskinesia test. Athletes were followed for 16 weeks to monitor the presence of shoulder pain. All athletes were submitted to the same training protocol. During the 16 weeks, 28.5% of the athletes (n=8) experienced shoulder pain in the dominant limb higher than 3 according to Numerical Rating Scale criteria; 71.5% of the athletes (n=20) did not experience pain, or pain equal or lower than 3. The main result of our study was that the odds of feeling pain higher than 3 was significantly higher among players who presented higher values for internal rotation peak torque (OR=1.113, CI 95%=1.006 to 1.232 and p=0.038). The odds of feeling pain increased by 11% for every N·m of the internal rotator muscles. Pre-season isokinetic rotator strength assessments can help identify adolescent volleyball players at increased risk of a shoulder injury.

Sarcopenia in knee osteoarthritis: the association with clinical and sonographic findings, physical function, and nutrition.

The purposes of this study were to examine to (1) the relation between OA and sarcopenia and to identify the most practical, easily accessible, and inexpensive method for investigating sarcopenia; (2) evaluation of sarcopenia risk factors in patients with OA. One hundred two patients with clinical and radiological diagnosis of knee osteoarthritis and 33 healthy control subjects were included in the study and all subjects were evaluated for sarcopenia. Dual-X-ray absorptiometry (DEXA) is used to measure body composition parameters and muscle thickness measurements with ultrasonography for diagnosis of sarcopenia. The mean age of the group with sarcopenia was statistically higher than the other two groups (p < 0.001). The weight, body mass index (BMI), waist circumference, upper-mid-arm circumference, thigh, and leg circumference of osteoarthritis (OA) patients with sarcopenia were statistically lower than those of non-sarcopenic and control group (p < 0.01, p < 0.001). Body composition parameter results showed that sarcopenic patients had statistically lower values as fat mass, lean body mass, and skeletal muscle index (p < 0.001, p = 0.001, p < 0.001, respectively) than those of non-sarcopenic and control group and fat mass index values (p = 0.012) are lower than the non-sarcopenic group. With respect to sarcopenia, the effect of adiponectin and leptin levels were not detected. It was determined that body composition values measured with DEXA, ultrasonographic measures, isokinetic muscle strength assessment, handgrip strength, and gait speed had predictive values for sarcopenia. We found that patients with sarcopenic OA were older, weaker, undernourished, and restricted in their level of physical activity in the study. Among the methods of determining sarcopenia, ultrasound becomes prominent with its practical, cheap, and easily accessible features. We think that our results will increase the awareness of the presence of sarcopenia in OA patients.