Extension Peak Research Articles

Isokinetic strength testing with different biomechanical demands on core strength: a comparison of military competitive athletes and soldiers with high occupational physical strain

It is known that anthropometric data (weight, height, BMI, waist circumference and WHtR) and male gender are positively correlated with greater core strength, while age is negatively correlated. For competitive athletes with no significant differences in the anthropometric data stated above, there have hardly been any studies in which isometric core strength in a seated position is quantitatively compared among athletes in different sports. This study aimed to analyse different sports in well-trained athletes using military competitive sports as an example with regard to possible differences in core strength. For this purpose, Parachuting (n=28), Military Pentathlon (n=34) and Ski Platoon (n=38) groups were compared with regard to isokinetic core strength using dynamometry in seated position. In addition to the comparison of anthropometry and isokinetic results with descriptive statistics, ANOVA and Welch-ANOVA were used to compare the means of absolute and weight-adjusted core strength. It was shown that the Ski Platoon group had significantly higher flexion peak torque values than the Military Pentathlon and Parachuting groups. Even when adjusted for weight, the values were significantly higher than those measured in the Military Pentathlon group but not significantly higher than those in the Parachuting group. For extension peak torque, it was found that the Military Pentathlon group had significantly lower values than the Ski Platoon group and, in the weight-adjusted analysis, significantly lower values than the Parachuters. Using the example of competitive military sports, this study was able to show that there are significant differences in isokinetic core strength even among professional competitive athletes.This knowledge should be used to carry out detailed quantitative analyses of core strength, even in well-trained professional athletes, to find applications for prevention or to coordinate compensating exercises.

How Humans Run Faster: The Neuromechanical Contributions of Functional Muscle Groups to Running at Different Speeds.

How the neuromechanics of the lower limb functional muscle groups change with running speed remains to be fully elucidated, with implications for our understanding of human locomotion, conditioning, and injury prevention. This study compared the neuromechanics (ground reaction and joint kinetics, kinematics and muscle activity) of middle-distance athletes running on an instrumented treadmill at six wide-ranging speeds (2.78-8.33 m·s-1). Ground reaction forces and kinematics were analyzed using inverse dynamics to calculate flexor and extensor joint torques, and positive and negative work done by these torques. Contributions of each functional muscle group to the total positive and negative work done by the limb during stance, swing, and the whole stride were quantified. During stance, the ankle plantar flexors were the major energy generator and absorber (>60%) at all speeds, but their contribution to whole stride energy generation and absorption declined with speed. Positive work by the hip extensors rose superlinearly with speed during stance (3-fold) and especially during swing (12-fold), becoming the biggest energy generator across the whole stride at >5 m·s-1. Knee flexor and extensor negative work also rose superlinearly with speed during swing, with the knee flexors becoming the greatest energy absorber over the whole stride at >7.22 m·s-1. Across speeds, plantar flexor peak moment and positive work accounted for 97% and 96% of the variance in step length, and swing hip extension peak moment and positive work accounted for 98% and 99% of the variance in step frequency. There were pronounced speed, phase (stance/swing), and work (positive/negative) dependent contributions of the different functional muscle groups during running, with extensive implications for conditioning and injury prevention.

Females with hip pain walk with altered kinematics at peaks and throughout the gait cycle

BackgroundFemales with acetabular dysplasia and/or labral tears (hip pain) exhibit altered walking kinematics, with studies reporting mixed results in sagittal and frontal planes compared to pain-free controls, often conducting only discrete analyses and warranting further investigation. The objective of this study was to investigate discrete and continuous hip and pelvic kinematics between females with and without hip pain in two walking conditions. MethodsWe collected kinematic walking data from 69 females (35 with hip pain, 34 controls) using motion capture and an instrumented treadmill in two conditions: preferred and fast (125% preferred). We used a general linear model and one-dimensional statistical parametric mapping to conduct discrete and continuous analyses comparing kinematics between groups, with and without adjustment for gait speed. FindingsThe hip pain group walked with reduced peak hip extension (Preferred: P = .046, Cohen's d = 0.41; Fast: P = .028, d = 0.48) and greater peak anterior pelvic tilt (Preferred: P = .011, d = 0.57; Fast: P = .012, d = 0.58) compared to controls. From continuous analyses, the hip pain group walked with reduced hip extension during terminal stance (Fast: P = .040), greater anterior pelvic tilt throughout (Preferred: P = .007; Fast: P = .004), and greater contralateral pelvic drop (Preferred: P = .045) during midstance. Adjusting for speed slightly affected p-values, but significance was retained for all prior variables except pelvic drop. InterpretationKinematic differences between individuals with and without hip pain may provide insight into potential predisposing factors for hip pathology and/or compensations for pain or pathological processes. This work furthers understanding of altered movement patterns in individuals with hip pain and may inform physical therapy treatments.

The Influence of Medial and Lateral Forefoot Height Discrepancy on Lower Limb Biomechanical Characteristics during the Stance Phase of Running

Previous research has predominantly focused on the biomechanical effects of anterior–posterior foot motion during running, with comparatively less attention given to medial–lateral foot motion and its impact on lower limb biomechanical characteristics. We recruited 18 healthy runners who wore five different types of running shoes: regular shoes (NS), those with a 6 mm and 9 mm medial–lateral height difference in the forefoot (M6, M9), and those with a 6 mm and 9 mm lateral–medial height difference (L6, L9). Biomechanical parameters of lower limb joints during the stance phase of running, including range of motion, peak angular velocity, peak moment, power, and work, were analyzed. We used paired-sample t-tests and one-dimensional statistical parametric mapping (SPM1D) to compare joint biomechanics between shoes with varying height differences and NS. Under the L6 condition, notable differences occurred in the hip and knee flexion–extension moments during landing and push-off, accompanied by a significant increase in ankle dorsiflexion work and a significant decrease in inversion–eversion work. In contrast, the M9 condition resulted in decreased hip flexion–extension peak moment, power, and work in the sagittal plane. These findings indicate that varying forefoot medial–lateral height differences in running shoes significantly impact lower limb joint dynamics during the stance phase, particularly the L6 condition, potentially reducing knee injury risk and aiding gait improvement for overpronators. The findings offer valuable insights for sports injury prevention and athletic footwear design. However, further research is needed to understand the underlying mechanisms and practical implications for sports injury prevention and performance enhancement.

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.

Evaluation of 25(OH) vitamin D3 and quadriceps strength correlation in postmenopausal women: A cross-sectional study.

Vitamin D deficiency is common in postmenopausal women and is associated with low vitamin D intake, increased age, decreased absorption. Especially at advanced age, vitamin D deficiency may increase muscle weakness and disbalance resulting in increased risk of fracture. This study aims to explore the correlation between 25(OH) vitamin D3 levels and quadriceps muscle strength in postmenopausal women. We evaluated bilateral qadriceps muscle strength in postmenopausal women with isokinetic test. We evaluated the correlation of muscle power with measurements of parathormone, vitamin D, Calcium, creatinine, alanine transaminase, alkaline phosphatase, total creatine kinase. The mean vitamin D level of 95participants included in the study was 18.24 ± 8.94ng/ml. Vitamin D levels were found to be deficient (< 10ng/ml) in 23 (24.1%), insufficient in 62 (65.26%) and normal in 10 (10.53%) of the 95participants. A weak negative correlation was observed between participants' vitamin D levels and PT values (r=-0.271, p= 0.012). A moderate negative correlation was found between ALP and vitamin D levels (r=-0.317, p= 0.002). However, there was no significant correlation between vitamin D levels and the 60∘ and 90∘ flexion and extension peak torque values (All p values > 0.05). Vitamin D levels and muscle strength weren't statistically significant. Few studies are available in the related literature, highlighting the need for further research to achieve a clearer consensus.

Biomechanical analysis of different back-supporting exoskeletons regarding musculoskeletal loading during lifting and holding

Industrial back support exoskeletons (BSEs) are a promising approach to addressing low back pain (LBP) which still affect a significant proportion of the workforce. They aim to reduce lumbar loading, the main biomechanical risk factor for LBP, by providing external support to the lumbar spine. The aim of this study was to determine the supporting effect of one active (A1) and two passive (P1 and P2) BSEs during different manual material handling tasks. Kinematic data and back muscle activity were collected from 12 subjects during dynamic lifting and static holding of 10 kg. Mean and peak L5/S1 extension moments, L5/S1 compression forces and muscle activation were included in the analysis. During dynamic lifting all BSEs reduced peak (12–26 %) and mean (4–17 %) extension moments and peak (10–22 %) and mean (4–15 %) compression forces in the lumbar spine. The peak (13–28 %) and mean (4–32 %) activity of the back extensor muscles was reduced accordingly. In the static holding task, analogous mean reductions for P1 and P2 of L5/S1 extension moments (12–20 %), compression forces (13–23 %) and muscular activity (16–23 %) were found. A1 showed a greater reduction during static holding for extension moments (46 %), compression forces (41 %) and muscular activity (54 %). This pronounced difference in the performance of the BSEs between tasks was attributed to the actuators used by the different BSEs.

Successful Powerlifting in a Unilateral, Transtibial Amputee: A Descriptive Case Series.

Beausejour, JP, Guinto, G, Artrip, C, Corvalan, A, Mesa, MF, Lebron, MA, and Stock, MS. Successful powerlifting in a unilateral, transtibial amputee: A descriptive case series. J Strength Cond Res 38(5): e243-e252, 2024-There are no reports in the literature of powerlifting success after amputation. We had the unique opportunity to characterize functional outcomes, strength, muscle contractility and size, and corticospinal excitability in an accomplished, competitive powerlifter (best competition squat = 205.0 kg, deadlift = 262.7 kg) with a unilateral, transtibial amputation relative to amputee controls. Four men (age range = 23-49 years) with unilateral, lower-limb amputation (3 transtibial, 1 transfemoral) participated in 1 laboratory visit. We assessed 10-m gait speed, the timed up and go (TUG) test, 5-time sit-to-stand performance (5TSTS), contractile properties of the vastus lateralis (VL) and medial gastrocnemius by tensiomyography, and VL cross-sectional area (CSA) by ultrasonography. Unilateral assessments for the intact limb included isokinetic knee extension and flexion torque and power and transcranial magnetic stimulation derived corticospinal excitability. An interview with the powerlifter provided contextual perspective. Compared with the control subjects, the powerlifter performed the 5TSTS faster (6.8%), exhibited faster VL contraction times (intact limb = 12.2%; residual limb = 23.9%), and showed larger VL CSA for the intact limb (46.7%). The powerlifter exhibited greater knee extension and flexion peak torque and mean power, particularly at 180°·s -1 , as well as greater corticospinal excitability for the intact VL (65.6%) and tibialis anterior (79.6%). By contrast, the control subjects were faster in the TUG (18.3%) and comfortable (13.0%) and fast (21.4%) in the 10-m walk test. The major themes of our interview included needing to modify lifting mechanics, persistence, and remarkable pain tolerance. Our findings highlight the impressive neuromuscular adaptations that are attainable after lower-limb amputation.

A hop testing alternative for functional performance following anterior cruciate ligament reconstruction.

The purpose of this work was to provide a simple method to determine reactive strength during the 6-meter timed hop test (6mTH) and evaluate its association with isokinetic peak torque in patients following anterior cruciate ligament reconstruction (ACLR). Twenty-nine ACLR patients who were at least four months from surgery were included in this analysis. Participants were brought into the laboratory on one occasion to complete functional testing. Quadriceps and hamstring isokinetic testing was completed bilaterally at 60, 180, and 300 deg∙s-1, using extension peak torque from each speed as the outcome measure. The 6mTH was completed bilaterally using a marker-based motion capture system, and reactive strength ratio (RSR) was calculated from the vertical velocity of the pelvis during the test. An adjustment in RSR was made using the velocity of the 6mTH test to account for different strategies employed across participants. Repeated measures correlations were used to determine associations among isokinetic and hop testing variables. A two-way mixed analysis of variance was used to determine differences in isokinetic and hop testing variables between operated and non-operated legs and across male and female participants. Moderate positive associations were found between RSR (and adjusted RSR) and isokinetic peak torque at all speeds (r = .527 to .577). Mean comparisons showed significant main effects for leg and sex. Patients showed significant deficits in their operated versus non-operated legs in all isokinetic and hop testing variables, yet only isokinetic peak torque and timed hop time showed significant differences across male and female groups. Preliminary results are promising but further development is needed to validate other accessible technologies available to calculate reactive strength during functional testing after ACLR. Pending these developments, the effects of movement strategies, demographics, and levels of participation on RSR can then be explored to translate this simple method to clinical environments.

New prediction equations for knee isokinetic strength in young and middle-aged non-athletes

BackgroundThis study aimed to develop alternative prediction equations to predict isokinetic muscle strength at 60°/s based on anthropometric characteristics, including body mass, height, age, and sex for young and middle-aged non-athlete populations.MethodsThree hundred and thirty-two healthy non-athletic participants (174 females, 158 males) between 20 and 59 years underwent a 60°/s isokinetic knee joint concentric contraction test. Forty people were randomly selected for retesting to assess the reliability of the isokinetic instrument. Multivariate linear regression was used to establish extension peak torque (EPT) and flexion peak torque (FPT) prediction equations. Sixty extra participants were used individually to validate the prediction equations, and Bland Altman plots were constructed to assess the agreement of predicted values with actual measurements.ResultsThe result demonstrated that the instrument we used has excellent reliability. The multivariable linear regression model showed that body mass, age, and sex were significant predictors of PT (EPT: Adjusted R2 = 0.804, p < 0.001; FPT: Adjusted R2 = 0.705, p < 0.001). Furthermore, the equations we established had higher prediction accuracy than those of Gross et al. and Harbo et al.ConclusionThe equations developed in this study provided relatively low bias, thus providing a more suitable reference value for the knee isokinetic strength of young and middle-aged non-athletes.

The Influence of Strength Level on Handball-Specific Fitness Elements Between Stronger and Weaker Professional Players.

Kyriacou-Rossi, A, Hadjicharalambous, M, and Zaras, N. The influence of strength level on handball-specific fitness elements between stronger and weaker professional players. J Strength Cond Res 38(5): 966-975, 2024-The aim of the study was to investigate the influence of strength level between stronger and weaker handball players on handball specific fitness elements and to explore the correlations between strength and sport-specific fitness elements. Twenty-one professional male handball-players (age: 25.9 ± 6.9 years; mass: 87.9 ± 13.9 kg; height: 1.81 ± 0.08 m), participated in the study. Players were divided into the stronger (SG) and weaker group (WG) according to their relative to body mass 1 repetition maximum strength (1RM). Measurements included body composition, countermovement jump (CMJ), isometric leg extension peak torque (IPT) and rate of torque development (RTD), 5-step long-jump, 0-20 m linear sprint, T-half test, throwing velocity, and 1RM in bench press and squat. No significant difference was found for body composition between SG and WG ( p > 0.05). However, SG had significantly higher CMJ height (21.5%, p = 0.002), IPT (22.4%, p = 0.008), RTD relative to body mass ( p < 0.05), 5-step long jump (10.9%, p = 0.005), lower 0-20 linear sprint (-6.3%, p = 0.012), lower T-half test time trial (-7.3%, p = 0.001), and higher throwing velocity compared with WG ( p < 0.05). When all players included in one group, large to very large correlations were found between 1RM strength and IPT with fat-free mass ( r = 0.518-0.774) and throwing velocity ( r = 0.472-0.819). Very large correlations were found between RTD with fat-free mass ( r = 0.760) and throwing velocity ( r = 0.780-0.835). Stronger players have greater performance in all handball-fitness attributes compared with their weaker counterparts. The significant correlations between handball-specific fitness elements with strength and RTD suggest that strength training is essential for handball players as it may link to higher on court performance.

The relationship between visual function and physical performance in the Study of Muscle, Mobility and Aging (SOMMA).

The relationship of types of visual function to different aspects of physical function, especially strength and coordination, has been understudied, but delineation of these relationships could suggest potentially modifiable targets prior to the onset of disability. Cross-sectional analysis of visual function (self-reported eyesight and eye disease, visual acuity, contrast sensitivity) and physical function tests in 877 older adults (mean age 76.36±5.01 years, 59.2% women, and 13.3% Black race). Separate linear regression models were constructed for short physical performance battery (SPPB), expanded SPPB (eSPPB), their components (gait speed, chair stand, balance, narrow walk), stair climb, four-square step, leg extension peak power and strength, and grip strength. In adjusted models, worse acuity, worse contrast sensitivity, and self-reported poor vision were significantly associated with worse performance on the eSPPB and four-square step test. Worse contrast sensitivity, but not acuity, was significantly associated with shorter balance times, slower chair stand pace, longer stair climb time, and worse SPPB score. Associations of worse acuity and contrast sensitivity with weaker leg extension power, leg strength, and grip strength were attenuated by covariate adjustment. Self-reported macular degeneration, but not cataract or glaucoma, was associated with worse performance on SPPB, eSPPB, balance, stair climb, and four-square step tests in adjusted models. Worse contrast sensitivity and macular degeneration remained associated with worse SPPB and balance after controlling for visual acuity and self-reported eyesight. Poor contrast sensitivity was more strongly associated with worse physical performance than acuity, especially for complex tasks that dynamically challenge coordination and balance. Future studies should examine if older adults with contrast sensitivity impairment would benefit from targeted intervention to decrease their risk of disability.

Effect of Spinal Correction Surgery on Lower Limb Strength in Idiopathic Adolescent Scoliosis.

Objectives To analyze the lower limb strength in both untreated and surgically treated adolescent idiopathic scoliosis (AIS) patients and examine its correlation with the distance covered in a six-minute walking test (6MWT). Methods A total of 88 participants (n = 30 pre-surgery AIS patients, n = 30 post-surgical AIS patients, and n = 28 control) underwent a 6MWT and a muscle strength assessment. The lower limb strength was measured at the knee joint using the knee extension (KE) and knee flexion (KF) peak torque (PT) measurements. Results The control group covered a greater distance in the TC6 compared to both the pre-surgical (534 ± 67 m) and post-surgical (541 ± 69 m) groups, with a distance of 612 ± 70 m (p < 0.001). No differences were observed in KE PT (pre: 2.1 ± 0.63, post: 2.1 ± 0.7, control: 2.2 ± 0.7 Nm.kg -1 , p = 0.67) or KF PT (pre: 1.0 ± 0.3, post: 1.1 ± 0.3, control: 1.1 ± 0.5 Nm.kg -1 , p = 0.46). A moderate positive correlation was observed between KE PT and 6MWT distance (r = 0.53, p < 0.001), as well as a low positive correlation for KF PT (r = 0.37, p = 0.003) with 6MWT distance. Conclusion This study highlights the importance of lower limb maximal strength in the functionality of AIS patients. Our findings suggest that exercise programs aimed at enhancing lower limb strength, especially the KE, could improve the walking capacity of AIS patients. These results provide useful information for designing purposeful exercise programs for AIS patients with walking deficits.

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.

Effect of isokinetic muscle strength training on knee muscle strength, proprioception, and balance ability in athletes with anterior cruciate ligament reconstruction: a randomised control trial.

Objective: This study aimed to investigate the effects of regular isokinetic muscle strength training on knee muscle strength, proprioception, and balance ability in athletes after anterior cruciate ligament (ACL) reconstruction. Methods: Forty-one athletes who underwent ACL reconstruction were randomly divided into the experimental (n = 21) and control (n = 20) groups. The experimental group used an isokinetic muscle strength tester for 4weeks (five times/ week) of knee flexion and extension isokinetic muscle strength training. The control group used the knee joint trainer (pneumatic resistance) for the same exercise regimen as the experimental group. Results: 1) Four weeks when compared with the baseline. Experimental group: the knee flexion and extension PT (60°/s and 240°/s) increased by 31.7%, 40.3%, 23.4%, and 42.9% (p < 0.01), and the flexion muscular endurance increased by 21.4% and 19.7% (p < 0.01). The flexion and extension kinaesthesia and the 30° and 60° position sense decreased by 36.2%, 32.3%, 40.0%, and 18.9% (p < 0.05). The anterior-posterior and medial-lateral displacement and speed decreased by 30.2%, 44.2%, 38.4%, and 24.0% (p < 0.05). Control group: the knee peak torque (60°/s) increased by 18.8% (p < 0.01). The anterior-posterior and medial-lateral displacement and speed decreased by 14.9%, 40.0%, 26.8%, and 19.5% (p < 0.01). 2) After 4weeks, compared with the control group, the knee flexion and extension peak torque (60°/s), extension, peak torque (240°/s), and extension muscular endurance of the treatment group increased to varying degrees (p < 0.05). However, the kinaesthesia, 30° position sense, and anterior-posterior displacement decreased to varying degrees (p < 0.05). Conclusion: Adding regular isokinetic muscle strength training to rehabilitation training further improved the knee flexion and extensor strength and extensor endurance of athletes with ACL reconstruction, as well as enhanced the kinaesthesia and 30° position sense and the balance between the anterior and posterior directions. However, the treatment had limited effects on knee flexion kinaesthesia and muscle endurance.

Factors Associated With Sports Function and Psychological Readiness to Return to Sports at 12 Months After Anterior Cruciate Ligament Reconstruction: A Cross-sectional Study

Background: Sports function and psychological readiness to return to sports (RTS) are important outcomes when evaluating rehabilitation after anterior cruciate ligament reconstruction (ACLR). It is, however, unclear which specific factors contribute most to these outcomes. Purpose: To determine associations between demographic characteristics, objective measurements of physical function, patient-reported outcome measure scores, sports-related function assessed with the Knee injury and Osteoarthritis Outcome Score (KOOS) Sport and Recreation subscale, and psychological readiness to RTS assessed with the Anterior Cruciate Ligament–Return to Sport after Injury (ACL-RSI) scale at 1 year after ACLR. Study Design: Cross-sectional study; Level of evidence, 3. Methods: At a mean of 12.5 ± 2.0 months after ACLR, 143 participants (50.3% female), with a mean age of 25.0 ± 5.7 years, were assessed for demographic characteristics, physical factors (hop performance, muscle strength, ankle and hip range of motion), and psychological factors (KOOS Pain and Symptoms subscales, Perceived Stress Scale, fear of reinjury) as well as the KOOS Sport and Recreation subscale and ACL-RSI scale. Backward linear regression models were used to evaluate factors associated with sports function and psychological readiness to RTS. Results: Lower isokinetic knee extension peak torque (limb symmetry index) (B = 18.38 [95% CI, 3.01-33.75]), lower preinjury activity level (B = 2.00 [95% CI, 0.87-3.14]), greater knee pain (B = 0.90 [95% CI, 0.70-1.10]), shorter time between injury and reconstruction (B = 0.16 [95% CI, 0.05-0.26]), and greater fear of reinjury (B = 0.11 [95% CI, 0.01-0.20]) were associated with a worse KOOS Sport and Recreation subscore (R2 = 0.683). A shorter hop distance (B = 0.15 [95% CI, 0.00-0.29]) was associated with a lower ACL-RSI score (R2 = 0.245). Conclusion: A combination of knee muscle strength, activity level, knee pain, timing of surgery, and fear of reinjury accounted for approximately 70% of the variation in sports function at 1 year after ACLR. In contrast, there was only 1 weak association between physical function and psychological readiness to RTS at this time point. Thus, factors associated with current sports function are much better known than features related to psychological readiness to RTS.

Applicability of the seated step test for assessing thigh muscle sarcopenia in older individuals

Assessment of lower limb muscle mass and related functions in older individuals is important because of their essential role in maintaining locomotion and activities of daily living. Therefore, a simple and reliable method for assessing these parameters should be established. The seated step test is easy and safe and can be used to assess lower limb agility; however, its relationship to skeletal muscle mass and function remains unknown. The present study aimed to investigate the relationships between the seated step test and lower limb muscle mass and function. For the analysis, we included 85 participants aged 73.1 ± 6.0 years. The participants performed an alternate up-down leg step test for 10 s while seated in a chair. Lower limb muscle mass was measured using bioimpedance analysis. Skeletal muscle mass index (SMI) was calculated using the following equation: lower limb muscle mass (kg) / height2 (m2). As the muscle functional parameters, we measured the isometric knee extension peak torque (KEPT), knee flexion peak torque (KFPT), and rate of torque development (RTD) for isometric knee extension in all participants. The seated step test score had a significant relationship with KEPT, KFPT, and SMI, but not with RTD. In the single regression analysis, the seated step test significantly predicted KEPT, KFPT, and SMI. These results suggest that up-down seated step test can be a reliable method to estimate lower limb muscle size and function in older individuals.

Exploring the Preliminary Effects of Resistance Training on Total Brain-Derived Neurotrophic Factor (BDNF) Levels in Elderly Individuals: A Pilot Study

Background: Studies have shown that exercise modulates brain-derived neurotrophic factor (BDNF) levels, and resistance training, in particular, has received increasing attention for its potential to enhance BDNF production. Most studies investigating exercise-induced BDNF changes have focused on free or mature BDNF, while the measurement of total BDNF, encompassing both proBDNF and mature BDNF, may provide a more comprehensive understanding of BDNF regulation. This pilot study aimed to explore the preliminary effects of resistance training on total BDNF levels in elderly individuals participating in a resistance training program.&#x0D; Methods: A small sample of participants (n=6) was recruited and engaged in a structured resistance training program for 12 weeks, with 6 participants in a control group. Total BDNF levels were measured at baseline and post-intervention using reliable laboratory assessments. Additionally, an isokinetic dynamometer was used to determine muscle strength to explore the effect of the resistance training program on muscle performance.&#x0D; Results: The findings revealed a significant increase in total BDNF levels following the 12 week resistance training intervention (p&lt;0.05). However, improvements in physical performance measures, knee extension peak torque and isometric maximal voluntary contraction, were not observed.&#x0D; Conclusion: In conclusion, this pilot study provides preliminary evidence of the positive effects of a 12 week resistance training intervention on total BDNF levels. The measurement of total BDNF levels serves as an important marker in assessing the response to resistance training. Further research with larger sample sizes and longer intervention periods is warranted to further explore the relationship between resistance training and total BDNF levels and to confirm these preliminary findings. Understanding the impact of resistance training on total BDNF levels can have implications for optimizing training programs and potentially improving exercise-related outcomes.&#x0D; Keywords: muscle strength, exercise, brain-derived neurotrophic factor, neuroplasticity, healthy ageing.

Quantifying demands on the hamstrings during high-speed running: A systematic review and meta-analysis.

Hamstring strain injury (HSI) remains a performance, economic, and player availability burden in sport. High-speed running (HSR) is cited as a common mechanism for HSI. While evidence exists regarding the high physical demands on the hamstring muscles in HSR, meta-analytical synthesis of related activation and kinetic variables is lacking. A systematic search of Medline, Embase, Scopus, CINAHL, SportDiscus, and Cochrane library databases was conducted in accordance with the PRISMA 2020 guidelines. Studies reporting hamstring activation (electromyographic [EMG]) or hamstring muscle/related joint kinetics were included where healthy adult participants ran at or beyond 60% of maximum speed (activation studies) or 4 m per second (m/s) (kinetic studies). A total of 96 studies met the inclusion criteria. Run intensities were categorized as "slow," "moderate," or "fast" in both activation and kinetic based studies with appropriate relative, and raw measures, respectively. Meta-analysis revealed pooled mean lateral hamstring muscle activation levels of 108.1% (95% CI: 84.4%-131.7%) of maximal voluntary isometric contraction (MVIC) during "fast" running. Meta-analysis found swing phase peak knee flexion internal moment and power at 2.2 Newton meters/kilogram (Nm/kg) (95% CI: 1.9-2.5) and 40.3 Watts/kilogram (W/kg) (95% CI: 31.4-49.2), respectively. Hip extension peak moment and power was estimated as 4.8 Nm/kg (95% CI: 3.9-5.7) and 33.1 W/kg (95% CI: 17.4-48.9), respectively. As run intensity/speed increases, so do the activation and kinetic demands on the hamstrings. The presented data will enable clinicians to incorporate more objective measures into the design of injury prevention and return-to-play decision-making strategies.

Relationships between isokinetic knee and shoulder peak strength with maximal punch force in boxing athletes

BACKGROUND: Muscle strength in the upper and lower limbs is a major contributing factor to punch force and is one of the keys to success in boxing. OBJECTIVE: This study aimed to investigate the relationship between knee and shoulder strength and punching force in boxers. METHODS: Twenty-one boxers completed knee flexion, knee extension, shoulder external rotation and internal rotation isokinetic concentric contractions at slow (60∘/s) and fast (180∘/s) angular velocities. Maximal punch force tests included lead and rear straight arm punching were assessed using a force platform. RESULTS: Pearson’s correlation coefficients revealed that knee extension (r= 0.646–0.848) and knee flexion (r= 0.470–0.646) peak torques were moderately to very strongly correlated with maximal punching force in lead and rear arms. The shoulder internal rotation (r= 0.492–0.634) and shoulder external rotation (r= 0.441–0.588) peak torques were moderate to strongly correlated with maximal punching force. Moreover, knee extension peak torques at 60∘/s had higher correlation with maximal punching force. In contrast, shoulder internal rotation peak torques at 180∘/s had a larger correlation with maximal punching force. CONCLUSIONS: The main findings indicated the importance of the capacity to generate maximum knee extension and rapid shoulder internal rotation strength, contributing to punch force production.