Concentric Hamstring Research Articles

Kinematic, Neuromuscular and Bicep Femoris In Vivo Mechanics during the Nordic Hamstring Exercise and Variations of the Nordic Hamstring Exercise

The Nordic hamstring exercise (NHE) is effective at decreasing hamstring strain injury risk. Limited information is available on the in vivo mechanics of the bicep femoris long head (BFLH) during the NHE. Therefore, the purpose of this study was to observe kinematic, neuromuscular and in-vivo mechanics of the BFLH during the NHE. Thirteen participants (24.7 ± 3.7 years, 79.56 ± 7.89 kg, 177.40 ± 12.54 cm) performed three repetitions of the NHE at three horizontal planes (0°, 20° and −20°). Dynamic ultrasound of the dominant limb BFLH, surface electromyography (sEMG) of the contralateral hamstrings and sagittal plane motion data were simultaneously collected. Repeated measures analysis of variance with Bonferroni post hoc corrections were used on the in vivo mechanics and the kinematic and sEMG changes in performance of the NHE. Likely differences in ultrasound waveforms for the BFLH were determined. Significant and meaningful differences in kinematics and in vivo mechanics between NHE variations were observed. Non-significant differences were observed in sEMG measures between variations. Changes to the NHE performance angle manipulates the lever arm, increasing or decreasing the amount of force required by the hamstrings at any given muscle length, potentially changing the adaptive response when training at different planes and providing logical progressions ore regressions of the NHE. All NHE variations result in a similar magnitude of fascicle lengthening, which may indicate similar positive adaptations from the utilization of any variation.

Relationship between hamstring strength and hop performance at 8 and 12 months after ACL reconstruction with hamstring tendon autografts

BackgroundThe relationship between hamstring strength and hop performance after anterior cruciate ligament (ACL) reconstruction with hamstring tendon (HT) autografts has not been well elucidated. The aim was to investigate the relationship between eccentric hamstring strength, assessed with the NordBord, and concentric hamstring strength, assessed with the Biodex, with hop performance at 8 and 12 months after ACL reconstruction.MethodsRegistry study. Patients ≥ 16 years who had undergone primary ACL reconstruction with HT autograft, followed by muscle strength and hop tests at 8 and 12 months were included. Correlations of the relative hamstring strength (Nm/kg or N/kg) and limb symmetry index (LSI) with hop performance were analyzed. Pearson’s correlation coefficient, and coefficient of determination (r2) were used for statistical analysis.ResultsA total of 90 patients were included, of which 48 (53%) were women. The mean age at ACL reconstruction was 27.0 ± 8.0 years. Relative hamstring strength had significant positive correlations with hop performance, ranging from r = 0.25–0.66, whereas hamstring strength LSI had significant positive correlations which ranged from r = 0.22–0.37 at 8 and 12 months after ACL reconstruction. At 12 months, the relative hamstring strength in the Biodex explained 32.5–43.6% of the hop performance in vertical hop height, hop for distance relative to height, and the total number of side hops, whereas the relative hamstring strength in the NordBord explained 15.2–23.0% of the hop performance.ConclusionThe relative hamstring strength in the Biodex test explained 32.5–43.6% of the hop performance, whereas the relative hamstring strength in the NordBord explained 15.2–23.0%. Thus, our findings suggest that relative hamstring strength, especially in the hip-flexed position may be a better indicator of hop performance at 8 and 12 months after ACL reconstruction in patients treated with HT autograft.

Immediate but not prolonged effects of submaximal eccentric vs concentric fatiguing protocols on the etiology of hamstrings' motor performance fatigue.

Our study aimed to compare the immediate and prolonged effects of submaximal eccentric (ECC) and concentric (CON) fatiguing protocols on the etiology of hamstrings' motor performance fatigue. On separate days, 16 males performed sets of 5 unilateral ECC or CON hamstrings' contractions at 80% of their 1 Repetition Maximum (1RM) until a 20% decrement in maximal voluntary isometric contraction (MVC) torque was reached. Electrical stimulations were delivered during and after MVCs at several time points: before, throughout, immediately after (POST) and 24h (POST 24) after the exercise. Potentiated twitch torques (T100 and T10, respectively) were recorded in response to high and low frequency paired electrical stimulations, and hamstrings' voluntary activation (VA) level was determined using the interpolated twitch technique. For statistical analysis, all indices of hamstrings' motor performance fatigue were expressed as a percentage of their respective baseline value. At POST, T100 (ECC: -13.3%; CON: -9.7%; p < 0.001), T10 (ECC: -5.1%; CON: -11.8%; p < 0.05) and hamstrings' VAlevel (ECC: -3.0%; CON: -2.4%; p < 0.001) were significantly reduced from baseline, without statistical differences between fatigue conditions. At POST24, all indices of hamstrings' motor performance fatigue returned to their baseline values. These results suggest that the contribution of muscular and neural mechanisms in hamstrings' motor performance fatigue may not depend on contraction type. This may have implications for practitioners, as ECC and CON strengthening could be similarly effective to improve hamstrings' fatigue resistance.

Eccentric Muscle Strengthening Using Maximal Contractions Is Deleterious in Knee Osteoarthritis: A Randomized Clinical Trial.

Objectives: To show the superiority of eccentric versus concentric strengthening in terms of improving quadriceps strength in knee osteoarthritis (OA), a randomized controlled study was conducted to perform 12 sessions of either eccentric or concentric isokinetic muscle strengthening over 6 weeks. Methods: We recruited males and females, aged between 40 and 70 years, with predominantly unilateral femorotibial OA. Exclusion criteria were having a prosthesis, inflammatory arthritis or flare-up of OA, symptomatic patellofemoral OA, cardiovascular or pulmonary disease that could be a contraindication to the study treatment, and any pathology that could cause muscle weakness. The primary endpoint was the between-group difference in change in maximum concentric isokinetic knee extension peak torque (PT) at 60°/s on the OA side at 6 weeks. Secondary endpoints were between-group difference in change in concentric hamstring PT at 60°/s; eccentric quadriceps and hamstring PT at 30°/s; 10 m and 200 m walking speeds; pain and functional status (WOMAC score) at 6 weeks and 6 months. Results: The sample consisted of 11 females and 27 males, with a mean age of 57.7 ± 7.52 years and a body mass index (BMI) of 25.95 ± 3.93 kg/m2. Quadriceps strength increased more at 6 weeks in the concentric than the eccentric group with no statistical difference. There was a rate of 25% major adverse events in the eccentric group. Conclusions: Eccentric training resulted in a smaller improvement in quadriceps strength than concentric training and was associated with a high risk of muscle injury, particularly to the hamstring muscles.

Are accelerometer-measured sitting and physical activity times associated with muscle mass and strength in healthy young adults in the UAE?

BackgroundA high prevalence of obesity, sedentary behavior, and physical inactivity could affect muscle mass and strength in young adults in the United Arab Emirates (UAE). Therefore, we investigated the association of sex, body mass index (BMI), and accelerometer-measured sitting and physical activity (PA) times with skeletal muscle mass index (SMI), hand grip, and thigh muscle strength in healthy young adults in the UAE. MethodsIn this cross-sectional study, 156 healthy young adults (age 21.68 ± 3.01 years, BMI 25.40 ± 4.79 kg/m2, 52.6 % women) were included. BMI and muscle mass were recorded using a bioelectrical impedance analyzer. Maximum hand grip strength and thigh muscle torque were assessed using the Jamar-smart hand-dynamometer and Biodex System-4-Pro, respectively. Participants wore a triaxial Fibion accelerometer on their anterior thigh for >10 h per day for 4–7 days to measure their sitting and PA times. Multiple linear regression analyses were used. ResultsParticipants spent most of their time sitting (11.37 ± 1.10 h), followed by standing (2.92 ± 0.86 h), walking (1.58 ± 0.55 h), and vigorous intensity PA (4.79 ± 5.85 min) per 16-h day. Sex (p < 0.001) and BMI (p < 0.001) were negatively associated with all muscle mass and strength variables. Men had more muscle mass and strength than women. As BMI increased, muscle mass and muscle strength decreased. Accelerometer-measured sitting and walking times were negatively associated with concentric hamstrings (p = 0.044) and quadriceps torques (p = 0.031), respectively. ConclusionSex, BMI, and accelerometer-measured sitting and walking times were associated with muscle mass and/or muscle strength in healthy young adults. Women and those with a high BMI need interventions to improve their muscle mass and strength. The paradox regarding the association of PA with muscle mass and strength in younger adults may be due to possible influences from other factors (e.g., resistance training, dietary intakes, etc.) superseding that of accelerometer-measured PA.

A Novel Fixation Method of the Graft to the Fibular Head in Knee Lateral Collateral Ligament Reconstruction: Technical Note.

The lateral collateral ligament (LCL) is the strongest lateral stabilizer of the knee. It provides support against varus stress and posterolateral rotation of the knee. Lateral collateral ligament injuries mostly occur together with anterior and/or posterior cruciate ligament injuries. While grades 1 and 2 injuries are treated conservatively since they are partial injuries, total ruptures, as in grade 3, require surgical treatment. In conventional LCL reconstruction methods, hamstring grafts are used, and bioscrews are used in bone-tendon fixation. Lateral collateral ligament reconstruction is usually performed as a component of multiple ligament surgery. Therefore, there is a need for a contralateral hamstring tendon or allograft. The present article aims to define a technique that does not require tendon grafts and bioscrews in fibular fixation.

Contralateral hamstring autografts do not provide benefit compared to ipsilateral hamstring autografts in primary or revision anterior cruciate ligament reconstruction: a systematic review.

To evaluate the clinical outcomes of primary or revision ACL reconstruction (ACLR) after contralateral hamstring autografts versus ipsilateral hamstring autograft harvest. Three databases (MEDLINE, PubMed and EMBASE) were searched from inception to April 27th, 2023 for studies investigating contralateral hamstring autografts in primary or revision ACLR. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Data on demographics, strength measures, patient-reported outcome measures (PROMs), and rates of positive Lachman test, positive pivot-shift test and graft rupture were extracted. PROMs included Lysholm, International Knee Documentation Committee (IKDC) and Tegner scores. Nine studies comprising 371 patients were included in this review. In primary ACLR, there were no significant differences between contralateral and ipsilateral groups in isokinetic hamstring torque in the non-ACLR limb or isokinetic quadriceps torque in both limbs when tested at 60, 90, 120 or 180 degrees/second. Isokinetic hamstring torque in the non-ACLR limb was significantly weaker in the contralateral group at six months for primary ACLR; however, these deficits did not persist. There were no significant differences in postoperative median Tegner scores and Lysholm scores between contralateral and ipsilateral groups in primary ACLR. There were no significant differences in postoperative median Tegner, mean Lysholm and IKDC scores between groups in revision ACLR. There were no significant differences in positive Lachman, positive pivot-shift and rupture rates in primary ACLR between groups. Rates of positive Lachman and pivot-shift were slightly higher in the contralateral than ipsilateral group for revision ACLR. Contralateral hamstring autografts results in comparable muscle strength to ipsilateral hamstring autografts, with the exception of weaker hamstring strengths in the early postoperative period. Patient-reported outcome measures were similar between the two groups across both primary and revision ACLR, with rates of instability and failure being similar between groups for primary ACLR. Contralateral hamstring grafts do not provide additional benefit when compared to ipsilateral options for either primary or revision ACLR, and should be used only in select circumstances including insufficient ipsilateral hamstring grafts or situations where quadriceps or patella autografts are not optimal. Level IV.

Throwing Shoulder Range of Motion and Hamstring Flexibility in Adolescent Baseball Players: A Pilot Study.

Overhead throwing athletes with limited hamstring flexibility should be counseled appropriately regarding their risk for shoulder injury. Baseball players should stretch and prepare their bodies to throw to reduce the compensatory mechanisms that may occur from hamstring stiffness. We aim to identify the association between the contralateral hamstring-popliteal angle and throwing shoulder total range of motion (ROM) in high school baseball players. Fifteen high school varsity baseball players (ages 14-18 years old) volunteered for this observational study. All the athletes played five times a week and played different positions. Bilateral hamstring and throwing shoulder total ROMs were measured using a goniometer by the same examiner. Three examiners determined the maximum ROM by joint end feel for each measurement to ensure quality control. Contralateral hamstring flexibility was measured using the popliteal angle test. These measurements were compared to the throwing shoulder total ROM to determine the presence of an association. The relationship between the contralateral hamstring flexibility and throwing shoulder total ROM was determined using a linear regression analysis. The correlation coefficient (r) was +0.3928, indicating a positive linear relationship. We conclude that higher contralateral hamstring-popliteal angles may cause a compensatory increase in throwing shoulder total ROM. We highlight the role hamstring stiffness may play in shoulder injury development in adolescent baseball players.

Isokinetic thigh muscles strength in semi-professional athletics: A one season prospective cohort study

IntroductionContinuous evaluations of athletes, including strength testing, can help control performance improvement or facilitate the restoration of normality after an injury. The aim of the present study was to prospectively determine the peak torque (PT), angle at which PT is achieved, and functional ratios of flexors and extensors thigh muscles during one season. Material and methodsThirty semi-professional male athletes competing in long jumping (n = 10), javelin throwing (n = 10), and sprinting (n = 10) participated. PT was evaluated in relation to limb length; the angle at which PT was achieved was obtained from the force-curve displayed in the isokinetic dynamometer; functional ratios were calculated by dividing concentric hamstring strength by eccentric quadriceps strength (flexor ratio) or vice-versa for the extensor ratio. Assessment was performed at 60º/s and 300º/s. ResultsSignificant variations were seen for both extensor and flexor PTs at different stages of the season, with moderate to large effect sizes observed (effect size (d) = 0.49–0.93). Functional ratios and the angle at which peak torque was achieved remained stable throughout the season. ConclusionsThigh muscle strength is unstable throughout a track and field season, coaches or medical staff should consider these findings when programming training sessions or rehabilitating an athlete.

No Deficits in Functional Outcomes of the Contralateral Limb Are Seen When the Hamstring Is Harvested for Augmentation of Small Diameter Ipsilateral Hamstring Autograft

To evaluate clinical outcomes of the contralateral, nonoperative limb in patients undergoing contralateral hamstring (HS) autograft harvest compared with patients undergoing ipsilateral HS autograft harvest alone. This study included 96 patients who underwent isolated anterior cruciate ligament reconstruction (ACLR) using 4-stranded HS autograft (n= 85) or 4-stranded HS autograft augmented with contralateral HS (n= 13) due to inclusion of ipsilateral graft diameter <8 mm. Isokinetic flexion and extension strength and dynamic performance of the ipsilateral and contralateral limbs and limb symmetry index (LSI) were evaluated at 6 months' postoperatively. Rates of contralateral native ACL tear at minimum 2 years also were compared. For all comparisons, P < .05 was considered statistically significant. Normalized isokinetic knee flexion and extension strength of the contralateral limb did not differ between cohorts (P= .34; P= .21, respectively). LSI for knee extension peak torque and knee flexion peak torque did not differ between cohorts (P= .44; P= .67, respectively). No difference in LSI was seen for any dynamic performance testing (single leg hop, P= .97; triple leg hop, P= .14; 6-m timed hop, P= .99). No difference was observed in International Knee Documentation Committee (P= .99) or Knee Injury and Osteoarthritis Outcome Score subscale measures (P= .39-.86). No difference in rates of contralateral knee native ACL tears were seen between cohorts (HS autograft+ contralateral HS augmentation, n= 2, 15.4%; HS autograft, n= 7, 8.4%; P= .26). In this study, at the time of return to sport, we found no differences in contralateral limb functional performance or limb symmetry measurements between patients undergoing contralateral HS autograft harvest for augmentation of smaller (<8 mm) diameter HS autografts harvested from the injured extremity. Level III, retrospective cohort study.

At mid- to long-term follow-up after proximal hamstring tendon avulsion; there was greater fatty infiltration, muscle atrophy and strength deficit in the hamstring muscles of the injured leg than in the uninjured leg

BackgroundProximal hamstring tendon avulsions (PHAs) may be treated nonoperatively or operatively. Little is known about the result of the injury, and its treatment, on the quality and function of the hamstring muscle after healing and rehabilitation. We hypothesized that the injured leg would have greater fatty infiltration and atrophy than the uninjured leg at follow-up and that these findings would correlate to muscle weakness.MethodsIn a cross-sectional cohort study, 48 patients treated for PHA, either operatively or nonoperatively, were re-examined 2–11 years post-treatment. We measured muscle strength with isokinetic strength tests, and muscle volume and fatty infiltration with MRI.Primary outcomes were hamstring muscle quality, quantified by outlining the cross-sectional area slice-by-slice, and the degree of fatty infiltration estimated using the Goutallier grading method. Secondary outcome was concentric isokinetic hamstring muscle strength measured using BioDex at 60°/sec and tendon attachment assessed on MRI. Comparisons with the outcomes of the uninjured leg were made.ResultsThe total hamstring muscle volume was on average reduced by 9% (SD ± 11%, p < 0.001) compared to that of the uninjured leg. Fatty infiltration was significantly more severe in the injured hamstrings than in the uninjured hamstrings (p < 0.001). This was also true when only analyzing operatively treated patients. The reduction in muscle volume and increase in fatty infiltration correlated significantly (r = 0.357, p = 0.013), and there was also a statistically significant correlation with muscle atrophy and reduction in isokinetic strength (r = 494, p < 0.001).ConclusionPHA injuries result in fatty infiltration and muscle atrophy and the muscle quality impairment correlates with residual muscle weakness.

Diffusion tensor imaging and quantitative T2 mapping to monitor muscle recovery following hamstring injury.

MRI examinations are accurate for diagnosing sports-related acute hamstring injuries. However, sensitive imaging methods for assessing recovery of these injuries are lacking. Diffusion tensor imaging (DTI) and quantitative T2 (qT2) mapping have both shown promise for assessing recovery of muscle micro trauma and exercise effects. The purpose of this study was to explore the potential of DTI and qT2 mapping for monitoring the muscle recovery processes after acute hamstring injury. In this prospective study, athletes with an acute hamstring injury underwent a 3-T MRI examination of the injured and contralateral hamstrings including DTI and qT2 measurements at three time points: (1) within 1 week after sustaining the injury, (2) 2 weeks after time point 1, and (3) return to play (RTP). A linear mixed model was used for time-effect analysis and paired t-tests for the detection of differences between injured and uninjured muscles. Forty-one athletes (age 27.8 ± 7 years; two females and 39 males) were included. Mean RTP time was 50 (range 12-169) days. A significant time effect was found for mean diffusivity, radial diffusivity, and the second and third eigenvalues (p ≤ 0.001) in the injured muscles. Fractional anisotropy (p = 0.40), first eigenvalue (p = 0.02), and qT2 (p = 0.61) showed no significant time effect. All DTI indices, except for fractional anisotropy, were significantly elevated compared with control muscles right after the injury (p < 0.001). Values normalized during the recovery period, with no significant differences between control and injured muscles at RTP (p values ranged from 0.08 to 0.51). Mean qT2 relaxation times in injured muscles were not significantly elevated compared with control muscles at any time point (p > 0.04). In conclusion, DTI can be used to monitor recovery after an acute hamstring injury. Future work should explore the potential of DTI indices to predict RTP and recovery times in athletes after an acute strain injury.

Complication rate and isokinetic test performance of combined ACL repair and ALL reconstruction vs. ACL and ALL reconstruction: A matched-pair analysis at 6 months follow-up

There has been renewed interest in anterior cruciate ligament (ACL) repair procedures in the past decade. The aim of this study was to evaluate complication rate and isokinetic test performance in a matched pair analysis between patients who underwent ACL reconstruction and patients who underwent ACL repair + augmentation. A retrospective analysis of prospectively collected data was performed. Patients undergoing ACL repair + augmentation with anterolateral ligament reconstruction were propensity matched in a 1:1 ratio to patients who underwent ACL + ALL reconstruction. At 6 months follow-up, patients were clinically evaluated and underwent isokinetic test. The overall complication rate and the Limb Symmetry Index (LSI) were evaluated. The hamstring concentric and eccentric deficit was evaluated in relation to the non-operated limb. The study population comprised 98 patients (49 matched pairs). The repair group presented 8 (16%) patients with complications and the reconstruction group presented 4 (8%) patients with complications ( p = 0.22). Regarding the repair group, the complications were: 3 re-ruptures, 2 lateral meniscus lesions, 1 medial meniscus lesion and 2 cyclops syndromes. In the reconstruction group, the complications were: 2 cyclops syndromes, 1 lateral meniscus lesion and 1 medial meniscus lesion. Regarding the LSI, the repair group had 12 (24%) patients presenting a concentric hamstring test deficit, and 12 (24%) patients with eccentric hamstring test deficit. The reconstruction group had 18 (37%) patients with concentric hamstring test deficit and 16 patients (33%) with eccentric hamstring test deficit. The overall complication rate between patients who underwent ACL reconstruction and patients who underwent ACL repair + augmentation was not statistically different. Patients who underwent ACL repair + augmentation presented less hamstring deficit at the isokinetic test at 6 months follow-up.

Effects Of A Vibrating Foam Roller On The Work Of The Quadriceps And Hamstrings

PURPOSE: The purpose of this study was to compare the effects of a vibrating foam roller, a foam roller, and vibration-only on the dominant hamstrings, with a secondary aim of examining the effects on the quadriceps and non-dominant limb. METHODS: Fifteen resistance trained women (mean age ± SD = 22.9 ± 2.0 years, height = 162.7 ± 4.8 cm, body mass = 66.0 ± 9.7 kgs, BMI = 24.9 ± 3.3 kg·m2) completed 4 testing sessions consisting of a foam rolling, a vibrating foam rolling, a vibration-only, and a control condition, to compare their effects on the work of the quadriceps and hamstrings. Conditions were only implemented on the participant’s dominant hamstrings, while testing was performed on both of the participant’s limbs to investigate possible contralateral effects. Participants completed concentric dynamometer testing at 60°s·-1, 180°s·-1, and 300°s·-1 for hamstrings and quadriceps, and eccentric dynamometer testing at 60°s·-1 and 180°s·-1 on the hamstrings. RESULTS: For concentric hamstrings, the treated dominant limb decreased pre- to-post testing (p = 0.004), while the non-dominant untreated limb decreased only during the vibrating foam rolling condition at the 180°s·-1 velocity (p = 0.036). The work of the concentric hamstrings of both limbs also decreased as velocity increased (p < 0.001) and decreased pre- to-post testing (p = 0.004). For the eccentric hamstrings, the dominant treated limb decreased pre- to post-testing (p = 0.001). The work of the eccentric hamstrings of both limbs decreased as velocity increased (p = 0.005) and decreased pre- to-post testing (p = 0.009). For concentric quadriceps, the work of the treated dominant limb was greater than the non-dominant untreated limb (p = 0.011), and the treated dominant limb decreased pre- to-post testing, while the non-dominant untreated limb increased (p = 0.009). The work of the concentric quadriceps of both limbs also decreased as velocity increased (p < 0.001). CONCLUSIONS: Since it is possible vibrating foam rolling, foam rolling, and vibration-only could decrease the work of the limb, is recommended to avoid using these interventions prior to a training session.

Explosive hamstrings strength asymmetry persists despite maximal hamstring strength recovery following anterior cruciate ligament reconstruction using hamstring tendon autografts

PurposeTo investigate the differences in maximal (isometric and concentric peak torque) and explosive (rate of torque development (RTD)) hamstring and quadriceps strength symmetry between males and females during early- and late-phase rehabilitation after anterior cruciate ligament reconstruction (ACLR) using hamstring tendon (HT) autografts and to determine the interaction of time and sex on maximal and explosive strength symmetry.MethodsA total of 38 female and 51 male participants were assessed during early (3–6 months post-operative) and late (7–12 months post-operative) phases of rehabilitation following ACLR. Maximal (concentric and isometric peak torque) and explosive (isometric RTD) hamstring and quadriceps strength were assessed and presented as limb symmetry index (LSI).ResultsMaximal concentric hamstrings asymmetry (Early: 86 ± 14; Late 92 ± 13; p = 0.005) as well as maximal concentric (Early, 73 ± 15; Late 91 ± 12; p < 0.001) and explosive (Early: 82 ± 30; Late: 92 ± 25; p = 0.03) quadriceps asymmetry decreased from early to late rehabilitation. However, there were no significant changes in maximal isometric quadriceps strength and explosive isometric hamstring strength in the same time period. Females had a larger asymmetry in maximal concentric (Females: 75 ± 17; Males: 81 ± 15; p = 0.001) and explosive (Females: 81 ± 32; Males: 89 ± 25; p = 0.01) quadriceps strength than males throughout rehabilitation. There were no sex differences in maximal and explosive hamstring strength. There were no sex by time interactions for any variables.ConclusionExplosive hamstring strength asymmetry did not improve despite recovery of maximal hamstring strength during rehabilitation following ACLR with HT autografts. While sex did not influence strength recovery, females had larger maximal and explosive quadriceps strength asymmetry compared to males throughout rehabilitation following ACLR.Level of evidenceLevel III

Are 6-Month Functional and Isokinetic Testing Measures Risk Factors for Second Anterior Cruciate Ligament Injuries at Long-T Follow-Up?

Second anterior cruciate ligament (SACL) injuries are a devastating complication following return to sport (RTS). Appropriate and safe RTS criteria that reduce the risk of SACL injuries are needed. The goal of this study was to investigate the relationship between functional and isokinetic testing at 6 months following primary ACL reconstruction (ACLR) as risk factors for SACL injuries. Patients with primary ACLR from 1990 to 2010 were identified. Those with 6-month postoperative functional and isokinetic testing and a minimum of 2-year follow-up were included. Functional testing included vertical jump, single-leg hop, and single-leg triple hop. Isokinetic testing included concentric quadriceps and hamstrings (HSs) strength at 60 and 180 degree/s speeds. Statistical analysis evaluated the significance of the various tests between those with and without a secondary tear. In total, 344 patients with a mean age of 26.0 ± 9.8 years at an average time of 9.1 ± 3.5 years of follow-up were analyzed. Fifty-nine patients (17%) experienced SACL injuries at an average time of 4.8 years following ACLR with 34 (58%) ipsilateral graft ruptures and 25 (43%) contralateral tears. Several isokinetic measures were significantly different between the NO SACL and the SACL groups: quadriceps 60 degree/s limb symmetry index (LSI) (75 vs. 82% p = 0.01), HS 60 degree/s LSI (92 vs. 97%, p = 0.04), quadriceps 180 degree/s involved/body weight (BW) (41 vs. 47%, p = 0.04), and HS 180 degree/s involved/BW (30 vs. 34%, p = 0.04). Patients with involved limb peak quadriceps torque value greater than 65 or 50% of BW (60 and 180 degree/s) had a 2.2 and 3.1 times higher risk of an SACL injury. Patients with certain elevated isokinetic scores in the injured limb at 6 months after ACLR experienced a higher rate of subsequent ACL injuries than those who had lower peak torque. Although a quantitative only analysis may not be sufficient to determine RTS criteria, clinicians should caution high-performing patients about the risk of subsequent ACL injury. Cohort study; 3.

Bilateral asymmetry of hamstring to quadriceps isokinetic torque ratio in different angular velocities in professional basketball players

BackgroundBilateral symmetry evaluation in lower limb is used for injury prevention, and is an indicator of returning to post-injury activity. The aim of present study was to investigate the effect of different angular velocities on asymmetry of the hamstring-to-quadriceps strength ratio. MethodIsokinetic concentric hamstring to quadriceps (H:Q) peak torque ratio of the 27 male and female professional basketball players was measured at seven angular velocities (60, 90, 120, 150, 180, 180, 240, 300 deg s−1) on both dominant and non-dominant legs with Biodex Isokinetic Dynamometer. Repeated measure analysis of variance was used to assess the effects of angular velocity and limb side on our outcomes (p≤ 0.05). ResultsThe results showed that with increasing angular velocity, the ratio of hamstrings to quadriceps increases (p = 0.001). There was no difference between dominant and non-dominant limbs in the H:Q peak torque ratio (p = 0.254). In addition, velocity of measurement did not affect the bilateral asymmetry of peak torque ratio of the H:Q of both sides (p = 0.852). ConclusionsBased on the results of this study, it can be concluded that measurement velocity does not affect the bilateral asymmetry of the H:Q peak torque ratio of the dominant and non-dominant limbs. In clinical assessments of H:Q bilateral asymmetry, we suggest that physical trainer can assess bilateral asymmetry of H:Q with arbitrary angular velocities.

Comparison of the H:Q Ratio Between the Dominant and Nondominant Legs of Soccer Players: A Meta-analysis.

Soccer players often have a dominant (D) leg, which could influence the relative strength between the quadriceps and hamstrings. The hamstring-to-quadriceps (H:Q) ratio can be assessed on a dynamometer at various velocities to provide information on injury risk. To assess the concentric hamstrings and concentric quadriceps strength ratio (conventional H:Q ratio) assessed in D and nondominant (ND) legs at various speeds in male soccer players. A systematic literature search was completed from inception to 2020 in PubMed, Academic Search Ultimate, CINAHL, and SPORTDiscus. Keywords associated with the H:Q ratio were connected with terms for soccer players. Titles and abstracts were screened by 2 reviewers based on inclusion and exclusion criteria related to sex, playing level, language, and measurement. A total of 81 studies were reviewed and 17 studies (21%) were used. A meta-analysis with random effects modeling generated standardized mean differences with 95% CIs between legs and speeds. Level 3. A total of 38 cohorts were identified, with 14, 13, and 11 cohorts assessed at low, intermediate, and high velocities, respectively. The Quality Assessment Tool for Observational Cohort and Cross-sectional Studies from the National Institutes of Health was used. The mean H:Q ratio at low velocities was 59.8 ± 9.5% in D leg and 58.6 ± 9.9% in ND leg, 64.2 ± 10.7% (D) and 63.6 ± 11.3% (ND) at the intermediate velocity, and 71.9 ± 12.7% (D) and 72.8 ± 12.7% (ND) at the high velocity. Low, intermediate, and high velocities had small effects of 0.13, 0.10, and -0.06, respectively. Conventional H:Q ratios vary across velocities but did not differ between D and ND limbs in male soccer players. This study may provide the foundation to establish norms and clinically meaningful differences.

No differences found in long-term outcomes of a randomized controlled trial comparing ipsilateral versus contralateral hamstring graft in ACL reconstruction.

Contralateral graft harvest in primary ACL reconstruction is relatively uncommon and the long-term comparative of this approach relative to ipsilateral harvest has not been described. The purpose of this study was to evaluate ACL graft and contralateral rupture following ipsilateral or contralateral semitendinosus and gracilis (STG) graft harvest at follow-up of a minimum 10years post-reconstruction in the treatment of a complete ACL tear. Patients from a previous randomized trial were evaluated. The primary outcome measures were ipsilateral and contralateral reinjury as well as the International Knee Documentation Committee (IKDC) knee assessment form, the ACL Quality of Life questionnaire (ACL-QoL) and the Tegner activity scale. Participants completed four different single-leg hop tests and concentric knee flexion and extension strength were assessed on an isokinetic dynamometer. Of the original 100 patients, 50 patients (41.3 ± 9.5years of age, 31 males, 19 females) reported on re-injury at 12.6 ± 1.4years post-operative. Thirty-eight patients returned for full assessment and 12 responded by mail or phone survey. There were no differences between groups for graft rupture, contralateral injury, ACL-QoL score, IKDC categorization, or anterior tibial translation, though both groups experienced a reduction in the Tegner Activity Scale from their preinjury scores. There was no difference in knee flexor and extensor isokinetic concentric strength, or single leg hop test performance. Knee flexor strength limb symmetry index was reduced when measured in the supine relative to the seated position in both groups, indicating persistent deficits in knee flexor strength when measured in the supine position. Contralateral hamstring harvest does not put patients at an increased risk of a contralateral ACL tear and long-term outcomes of ACL reconstruction do not differ based on the side of graft harvest. Contralateral STG harvest may provide a safe alternative surgical option for select patients. Level II.

Comparison of the Agonist/Antagonist Tensional Balance of the Knee between Two Isokinetic Positions: A Pilot Study on a Sample of High-Level Competitive Soccer Players.

Isokinetic knee dynamometry evolves towards more precise techniques, such as the calculation of the functional ratio. This study evaluated the influence of an intermediate hip position called the unified reclined position (URP) compared to the classic sitting position, (CSP) on hamstring eccentric PT values (Hexc30) and conventional (Hcon60/Qcon60) and functional (Hexc30/Qcon60) ratios. Twenty Spanish high-level competitive soccer players (20.4 ± 4.44 years) were evaluated in CSP and in URP. The hip angle in URP (44°) was determined with a passive extensibility test (quadriceps and hamstrings), looking for an agonist/antagonist tension balance. The following were performed: three repetitions (60°/s) and five repetitions (240°/s) in concentric quadriceps and hamstrings mode; and three repetitions (30°/s) in concentric and eccentric for the hamstrings. At 30°/s, the CSP presents higher values of maximal eccentric hamstring strength than URP, (Dom + N-Dom leg (Nm): CSP = 148.3 ± 19.5 vs. URP 143.5 ± 23.2); p = 0.086 (n.s.). The conventional relationship did not show data justifying the preference for URP over CSP (p = 0.86 (n.s.)). However, although the functional index did not show significant values (p = 0.97 (n.s.), it did show a greater number of subjects with imbalances measured in URP (five in URP vs. two in CSP). An assessment angle of the hip closer to sports reality seems to favor the use of the URP as a complementary method to the CSP. These data stimulate new studies using URP together with the classic protocol.