Isokinetic Dynamometry Research Articles

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.

Morbidity of long head of the triceps motor branch neurotization to the axillary nerve: Retrospective subjective and objective assessment of triceps brachii strength after transfer

IntroductionMorbidity is considered to be negligible in Leechavengvongs transfer (LT) of the long head of the triceps onto the axillary nerve, but the assessment methods used may lack reproducibility. We assessed triceps strength after LT objectively by the isokinetic technique, addressing the following questions: Is strength lowered after LT compared to the healthy limb? And 2) is there a good correlation between isokinetic dynamometry and subjective assessment? HypothesisIsokinetic measurement shows a decrease in triceps strength at peak torque after LT compared to the healthy limb, and this morbidity is underestimated on subjective assessment. Material and methodsThis single-center retrospective study included patients undergoing LT for axillary nerve trunk palsy between 2008 and 2020, with M5 triceps preoperatively on the British Medical Research Council (BMRC) scale. Twenty patients, with a mean age of 25±9years (range, 15–48years) were assessed at a mean 58±47months (range, 6–174months). Elbow extension strength was assessed on a standardized questionnaire, BMRC isometric test and isokinetic test on an angular course of 90° at 60°/sec and 180°/sec concentrically and 30°/sec excentrically. ResultsStrength at 60°/sec and 180°/sec concentrically and 30°/sec excentrically was significantly lower than in the healthy limb: respectively, −17Nm, −15Nm, and −16Nm, (p<0.001) for a mean −23%. Loss of strength was mainly severe on isokinetic testing and mild on isometric testing. Seven patients reported contracture (35%), 12 fatigue (60%), and 3 weakness (15%). Satisfaction with extension strength was excellent or good for respectively 12 (60%) and 8 patients (40%). Triceps strength was graded BMRC M4 in 9 triceps (11%) and M5 in 11 (55%). DiscussionAfter LT, isokinetic measurement found generally severe loss of triceps strength, but without subjective impact on everyday life. Level of evidenceIV; retrospective study.

Association between Hip Center Position and Isokinetic Hip Muscle Performance after Anterolateral Muscle-Sparing Total Hip Arthroplasty

Background and objectives: The superior placement of the acetabular cup induced the delayed recovery of abductor muscle moment after total hip arthroplasty (THA) with a conventional posterior approach. The anterior-based muscle-sparing (ABMS) THA effectively reduces soft tissue damage, including muscles. The influence of hip center position on anterior-based muscle-sparing (ABMS) total hip arthroplasty (THA) for post-operative hip muscle strength was unclear. We evaluate whether the hip center position affects the recovery of hip muscle strength after ABMS THA. Materials and Methods: The study was performed as a retrospective cohort study, and included 38 hips in 38 patients that underwent primary ABMS THA. Muscle strength was measured using isokinetic dynamometry before the operation, and at 6 and 12 months after surgery. The horizontal and vertical centers of rotation (H-COR and V-COR), vertical shift (V-shift), leg length, and global femoral offset were determined radiographically in reference to a previous report. Results: A weak negative correlation was observed between abduction muscle strength at 6 months and V-shift; a V-shift more than 15 mm demonstrated significantly decreased abductor muscle strength at 6 months. Conclusions: The superior placement of the hip center caused delayed recovery of abductor muscle strength in hips with anterolateral minimally invasive THA. There seems to exist no biomechanical reason why the same should not also be the case for the muscle-sparing approach.

The hamstrings to quadriceps functional ratio expressed over the full angle-angular velocity range using a limited number of data points.

The hamstring to quadriceps (H : Q) strength ratio is widely used to identify individuals at risk of sustaining hamstring strain injuries. However, its efficacy is not supported by the current evidence. Current methods for the calculation of the H : Q ratio provide only a one- or two-dimensional ratio, often ignoring fundamental muscle mechanical properties. Based on isokinetic torque measurements of the knee flexors and extensors (0–400° s−1) in 25 young, physically active males, we derived a model equation that creates a three-dimensional H : Q functional ratio profile. The model robustness was tested against a different number of input torque data (8, 11, 14 and 17 pairs of points) and small perturbation of the knee joint angle data (5°). The model was consistent and behaved well under all conditions apart from the eight pairs of points (R2 = 0.84−0.96; RMSE = 0.14−0.25; NRMSE = 0.12−0.27), and the H : Q functional ratio was successfully described even at angles and velocities that cannot be normally assessed with isokinetic dynamometry. Overall, our results suggest that the model can provide a fast and accurate three-dimensional description of the knee joint muscle strength balance using as few as 11 experimental data points and this could be an easy-to-employ screening tool.

Methodological considerations for assessing whole-body strength capacity through isometric dynamometry

ABSTRACT The present study aimed to explore the possibility of comprehensively assessing whole-body muscle strength by testing as few muscle groups as possible, using a single testing method (isometric or isokinetic dynamometry) and a single variable (maximal force or rate of force development). Knee, hip, shoulder and elbow extensors and flexors were evaluated in males with high (n = 26) and low strength levels (n = 32). The principal component analysis revealed three factors that explained 62.5% of the total variance, while the main factors were loaded by the different testing methods and strength variables for the muscles acting on the knee (first component), hip (second component) and arm joints (third component). These results were confirmed by a three-way ANOVA which revealed a significant factor of group (P < 0.001) and the interaction test type × group (P = 0.002), but not of test type (P = 0.644), muscle group (P = 0.999), or their interactions (P > 0.205). The correlations of strength outcomes across the muscles ranged from trivial to very large (r range = −0.17, 0.84), being generally higher for the antagonistic muscles. Overall, a comprehensive assessment of whole-body muscle strength can be obtained using isometric dynamometry and maximal force, but it should consider at least one muscle group from the antagonistic pair.

A low postabsorptive whole body protein balance is associated with markers of poor daily physical functioning in Chronic Obstructive Pulmonary Disease

Postabsorptive whole body protein kinetics are related to age, gender, body mass index (BMI), and habitual protein intake level. It is unclear how protein synthesis, breakdown, and postabsorptive protein balance rates are affected in Chronic Obstructive Pulmonary Disease (COPD)) and whether these relate to disease severity, lifestyle characteristics and poor daily functioning. We studied 91 COPD (GOLD 1-4) and 56 age matched control subjects without COPD or other chronic or acute health disease/condition in the postabsorptive state and measured body composition by Dual-energy X-ray Absorptiometry, and disease severity and comorbidities by medical screening, blood analysis and questionnaires. We assessed whole body production rates of phenylalanine and tyrosine by pulse stable isotope tracer infusion to calculate whole body protein breakdown (PB) and hydroxylation of phenylalanine to tyrosine, representative of postabsorptive protein balance. We measured muscle and cognitive function, and physical performance by isokinetic dynamometry, cognitive assessments, and 6-min walk test. We assessed physical activity level, mood and dietary protein intake by questionnaires. We measured plasma enrichments by LC-MS/MS and statistics by Fisher's exact test or analysis of covariance. Data are mean [95% CI]. The COPD patients had moderate to severe airflow obstruction, multiple comorbidities, and elevated values for plasma high sensitivity c-reactive protein (hs-CRP) and glucose. Although PB (3630 [3361, 3900] vs 3504 [3297, 3711] umol/h, p=0.1649) was not different, postabsorptive protein balance was lower in COPD patients (274.2 [242.4, 306.1] vs 212.9 [194.7, 231.0] umol/h, p<0.0001), both compared to control subjects. A lower postabsorptive protein balance was associated with age (p<0.0001) and higher levels for systolic blood pressure (p=0.0051) and hs-CRP (p=0.0046) but not with lung function. Furthermore, a lower postabsorptive protein balance level was associated with a lower intake of total calories and protein (p<0.0001) and lower muscle strength (p=0.0248), while only in COPD with a lower physical performance (p=0.0343). We found no association with cognitive function or mood. For all subjects, a cumulative model that included group, gender, age, BMI, systolic blood pressure, hs-CRP, caloric intake, protein intake, and leg strength was able to explain 55% of the variation in postabsorptive protein balance. These data suggest that systemic inflammation, high blood pressure and low protein intake are risk factors of a lower postabsorptive protein balance in COPD patients. A lower postabsorptive protein balance is associated with markers of poor daily physical functioning.

A Longitudinal Study of Quantitative Muscle Strength and Functional Motor Ability in Ambulatory Boys with Duchenne Muscular Dystrophy.

Duchenne muscular dystrophy (DMD) is an X-linked recessive genetic disorder, that is characterized by progressive muscle degeneration and loss of ambulation between 7-13 years of age. Novel pharmacological agents targeting the genetic defects and disease mechanisms are becoming available; however, corticosteroid (CS) therapy remains the standard of care. The purpose of this longitudinal study was to elucidate the effect of CS therapy on the rate of muscle strength and gross motor skill decline in boys with DMD and assess the sensitivity of selected outcome measures. Eighty-four ambulatory boys with DMD (49-180 months), 70 on CS, 14 corticosteroid naïve (NCS), participated in this 8-year multi-site study. Outcomes included; isokinetic dynamometry, the Standing (STD) and Walking/Running/jumping (WRJ) dimensions of the Gross Motor Function Measure (GMFM), and Timed Function Tests (TFTs). Nonlinear mixed modeling procedures determined the rate of change with age and the influence of steroids. Despite CS therapy the rate of decline in strength with age was significant in all muscle groups assessed. CS therapy significantly slowed decline in knee extensor strength, as the NCS group declined at 3x the rate of the CS group. Concurrently, WRJ skills declined in the NCS group at twice the rate of the CS group. 4-stair climb and 10 meter walk/run performance was superior in the boys on CS therapy. CS therapy slowed the rate of muscle strength decline and afforded longer retention of select gross motor skills in boys on CS compared to boys who were NCS. Isokinetic dynamometry, Walk/Run/Jump skills, and select TFTs may prove informative in assessing the efficacy of new therapeutics in ambulatory boys with DMD.

Abstract P196: Hand Grip Strength, Gait Speed And Incident Heart Failure In Older Adults

Title: Hand Grip Strength, Gait Speed and Incident Heart Failure in Older Adults Introduction: Heart failure (HF) is predominantly a disorder of older adults. Its cardinal feature, decreased exercise tolerance, results from both central (cardiac) and peripheral (skeletal muscle) dysfunction. Skeletal muscle weakness and frailty are common aspects of aging that are associated with vascular disease and may predispose to HF onset. Although simple measures of physical function like hand grip strength and gait speed have been linked to disability and mortality, their individual associations with incident HF in elders remain unclear. The relationship of these measures with onset of HF subtypes has not been previously studied. Hypothesis: We tested the hypothesis that lower grip strength and gait speed are independently associated with higher risk of HF and its subtypes (preserved [HFpEF] and reduced [HFrEF]). Methods: A total of 7,144 participants free of prevalent HF with available muscle measures were pooled from two prospective older cohorts, the Cardiovascular Health Study (n=4584) and the Health, Aging, and Body Composition Study (Health ABC) (n=2560). Grip strength was assessed by dynamometry, and gait speed based on a short-distance walk (calibrated to ~4 m in both studies). In a secondary analysis, we evaluated thigh muscle strength, assessed by isokinetic dynamometry in Health ABC only. Incident HF and its subtypes were adjudicated with similar methods in both studies. Cox models were fitted to estimate risks of incident HF after adjustment for potential confounders (age, sex, race/ethnicity, body mass index, smoking, alcohol, systolic blood pressure, antihypertensive medication, diabetes, coronary heart disease, cerebrovascular disease, peripheral artery disease, atrial fibrillation, forced expiratory volume in 1 second, albumin, estimated glomerular filtration rate). Results: Median age was 72, 42.2% were male, and 22.9% Black. Lower gait speed was significantly associated with higher incident HF (HR per SD = 1.16 [95% CI = 1.10-1.23]) after full adjustment, but this was not observed for lower grip strength (HR per SD = 1.02 [0.95-1.10]). Gait speed showed consistent inverse associations with both HF subtypes: HFpEF: HR per SD = 1.23 [1.10-1.36]); HFrEF (HR per SD = 1.15 [1.03-1.27]). Thigh muscle strength was not significantly associated with incident HF in Health ABC (HR per SD = 1.11 [0.95-1.30]). There was no evidence of effect modification by race or by cohort. Conclusion: In two prospective cohorts of older adults of mixed race, lower gait speed, but not strength, was associated with higher risk of HF and its subtypes. Whether this readily obtainable measure of functional capacity could be used for HF risk stratification and targeting of preventive interventions will require further study.

Influence of lower-limb muscular and tendon mechanical properties and strength on countermovement jump performance.

The aim of the study is to examine the relationship between measures of muscle and tendon mechanical properties and strength on countermovement jump (CMJ) performance. Twenty-six physically active participants (males; N.=16: females; N.=10) were tested. Testing comprised of measuring the mechanical properties of lower limb muscles and tendons using myotonometry, isometric and isokinetic knee extensor strength through dynamometry, and CMJ's with a force platform. Large positive correlations were observed between CMJ jump height and Achilles tendon stiffness (N/m) (r=0.56) and Achilles tendon tone (Hz) (r=0.553). Large negative correlations were found between CMJ height and Achilles tendon elasticity (r=-0.658), and Achilles tendon relaxation (r=-0.572), and Achilles tendon creep (r=-0.589). Large correlations (r=0.592 to 0.659) were observed between CMJ height and all measures of isometric and isokinetic dynamometry measures. Achilles tendon stiffness, elasticity level and relaxation, and isokinetic peak concentric torque (N.m) explained 63% of this variance. Greater stiffness of the Achilles tendon may improve CMJ performance due to the improved transfer of concentric and eccentric force of the knee extensor muscles. Practitioners need to implement specific interventions to target increasing Achilles tendon stiffness to improve countermovement jump performance.

Mitochondria-targeted antioxidant supplementation does not affect muscle soreness or recovery of maximal voluntary isometric contraction force following muscle-damaging exercise in untrained men: a randomized clinical trial.

Unaccustomed exercise causes muscle damage resulting in loss of muscle function, which may be attributable to exercise-induced increases in skeletal muscle reactive oxygen species. This study examined the effect of mitochondria-targeted antioxidant supplementation on recovery of muscle function following exercise. Thirty-two untrained men received MitoQ (20mg/day) or a placebo for 14 days before performing 300 maximal eccentric contractions of the knee extensor muscles of 1 leg. Muscle function was assessed using isokinetic dynamometry before, immediately after, and 24, 48, 72, and 168 hours after exercise. Muscle soreness was assessed using a visual analogue scale 24, 48, 72, and 168 hours after exercise. Blood samples were collected before, immediately after, and 2, 24, 48, 72, and 168 hours after exercise and urine samples were collected before and during the 48 hours after exercise. The reduction in maximal voluntary isometric contraction force and peak concentric torque following exercise was unaffected by MitoQ while recovery of peak eccentric torque was delayed in the MitoQ group. Exercise-induced increases in urine F2-isoprostanes were unaffected by MitoQ. MitoQ augmented exercise-induced increases in plasma creatine kinase levels, while plasma IL-6 was similar between groups. Muscle soreness was not affected by MitoQ. These results indicate that MitoQ does not attenuate post-exercise muscle soreness and may delay recovery of muscle function following eccentric exercise. Trial registration number: ACTRN12620001089921. Novelty: Post-exercise recovery of maximal voluntary isometric contraction force and peak concentric torque were unaffected by MitoQ. MitoQ delayed post-exercise recovery of peak eccentric torque. Post-exercise muscle soreness was unaffected by MitoQ.

Effect of Application of Repeated Downhill Walking Bouts on Ankle Isokinetic Parameters in Children with Obesity.

Background Obesity among children became of high concern. Obesity can affect many health aspects including muscular strength. Downhill walking is a useful intervention to enhance muscular strength, especially in older adults. Objective The current study's purpose was to investigate the effect of repeated bouts of downhill walking on ankle isokinetic parameters in children with obesity. Methods 32 obese male children aged from 8 to 12 years engaged in the study. The children were divided into two groups: the level walking group (LWG) (n = 16) and the downhill walking group (DWG) (n = 16). Participants in both groups walked 20 minutes on the treadmill, two sessions per week for 6 weeks, with a speed of 5 km/h, and the treadmill slope used for the DWG was set at –20%. Isokinetic dynamometry (Cybex 6000) was used to analyze the normalized eccentric and concentric torque of both ankle dorsiflexors and plantar flexors of the dominant leg in all participants. Results The normalized peak torques for eccentric plantar flexion, concentric plantar flexion, eccentric dorsiflexion, and concentric dorsiflexion significantly increased by 38.66%, 23.87%, 38.58%, and 15.51%, respectively, after repeated bouts of downhill walking. Level walking resulted in nonsignificant improvement in the muscular torques. Conclusion Downhill walking is a beneficial intervention in improving ankle muscular torques of obese children.

Associations of serum IL-6 with muscle, bone, and adipose tissue in women

This cross-sectional study examined the associations between serum interleukin-6 (IL-6) and muscle, bone, and fat parameters in recreationally active women. One-hundred forty-five women (48.7 ± 17.8 years; 164.4 ± 7.1 cm; 66.8 ± 10.7 kg; and 24.7 ± 3.9 kg/m2) underwent dual energy x-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) assessments to determine total and regional muscle, bone, and fat parameters. Muscle performance of the knee extensors was examined via isometric, isotonic, and isokinetic dynamometry assessments, and serum IL-6 was measured via enzyme linked immunosorbent assay. Serum IL-6 was inversely associated with thigh muscle cross-sectional area (mCSA, r = -0.28, p < 0.01); isometric strength (r = -0.19, p < 0.05); hip areal bone mineral density [aBMD] (r = -0.18, p < 0.05); trochanter aBMD (r = -0.23, p < 0.01); total body aBMD (r = -0.20, p < 0.05); cortical volumetric bone density at 38 and 66% tibia (r = -0.18 and r = -0.19, respectively, both p < 0.05), and 66% cortical thickness (r = -0.17, p < 0.05). These associations were present after adjusting for age, BMI, and physical activity. Thigh mCSA was significantly lower in the tertile possessing the greatest IL-6 compared to the lowest tertile (p < 0.01); after adjusting for age, body mass index, and physical activity. Collectively, these observations indicate that IL-6 is inversely associated with skeletal muscle and bone parameters independent of relevant confounders. These observations bolster the prognostic value of serum IL-6.

Quantification of Eccentric Hamstrings Strength in Elite Academy Footballers: Considerations for Assessment

Quantification of eccentric hamstring strength within elite youth sporting populations is a contemporary issue within practice. The aim of the study was to identify the reliability of eccentric strength metrics obtained via isokinetic dynamometry (IKD) and the NordBord in an elite youth football population. Furthermore, relationships between the strength metrics exhibited by the two devices were observed, to ascertain whether level of performance on one device can indicate how athletes will perform on the other. Twenty-one elite academy footballers completed two measures of eccentric hamstring strength on each device (60°·s-1 and 180°·s-1). Test-retest reliability was determined through Pearson correlation analysis. Relationships between strength metrics (IKD: PT, AvT and oPT at 60°·s-1 and 180°·s-1; NordBord: PF, AvF, PT, AvT, Ɵ) obtained on both devices were identified for analysis. Test-retest of both devices identified significant correlations for all eccentric strength metrics (P=≤0.05). Significant unilateral (L) relationships between PT, AvT (IKD 60°·s-1; 180°·s-1), break angle (Ɵ) (NordBord) angle peak torque (oPT) at 60°·s-1 and Ɵ were identified (P=≤0.05). Eccentric hamstring strength analysis on both the IKD and NordBord provide reliable information for practitioners, justifying their inclusion as one factor that may inform readiness to train and injury risk, within elite youth footballers. Although, careful consideration in relation to individual metrics must be given when informing decision making processes. Practitioners require clarity on the objectives of the assessment, what the strength metrics represent and how they provide insight into performance and injury risk.

Evenness of Dietary Protein Intake Is Positively Associated with Lean Mass and Strength in Healthy Women.

Background:Evenness of protein intake is associated with increased lean mass, but its relationship with muscle strength and performance is uncertain.Objectives:We determined the association of evenness of protein intake with lean mass, muscle strength and endurance, and functional ability.Design:This was a cross-sectional study.Setting:Data were collected at a research university in the upper midwestern United States.Participants:One hundred ninety-two healthy women, aged 18 to 79 years, mean ± SEM 41.9 ± 1.3, completed the study.Measurements:Dietary intake was assessed using 3-day food diaries verified with food frequency questionnaires. To assess evenness of protein intake, the day was divided into 3 periods: waking to 11:30, 11:31 to 16:30, and after 16:30. Lean mass was measured with dual energy X-ray absorptiometry. Lower-body muscle strength and endurance were determined using isokinetic dynamometry. Upper-body muscle strength was maximal handgrip strength. Functional ability was assessed using 6-m gait speed and 30-second chair stand tests. Accelerometry measured physical activity.Results:Intakes of 25 g or more of protein at 1 or more of the 3 periods was positively associated with lean mass (β ± S.E.; 1.067 ± 0.273 kg, P < .001) and upper-body (3.274 ± 0.737 kg, P < .001) and lower-body strength (22.858 ± 7.918 Nm, P = .004) when controlling for age, body mass index, physical activity, and energy and protein intakes. Consuming at least 0.24 g/kg/period for those under 60 years and 0.4 g/kg/period for those 60 years and older was related to lean mass (0.754 ± 0.244 kg, P = .002), upper-body strength (2.451 ± 0.658 kg, P < .001), and lower-body endurance (184.852 ± 77.185 J, P = .018), controlling for the same variables.Conclusions:Evenness of protein intake is related to lean mass, muscle strength, and muscular endurance in women. Spreading protein intake throughout the day maximizes the anabolic response to dietary protein, benefiting muscle mass and performance.

Influence of invertor and evertor muscle fatigue on functional jump tests and postural control: A prospective cross-sectional study

ObjectiveFatigue of the ankle's stabilizing muscles may influence the performance of functional activities and postural control. The purpose of this study was to evaluate the performance of healthy young adults using functional jump tests and static posturography control under pre- and post-fatigue conditions of the ankle invertor and evertor muscles. MethodsThirty physically active healthy male and female (15 male and 15 female) volunteers (24.3 years) were enrolled in this prospective cross-sectional study. Participants performed tests on one day under a non-fatigued state of invertor and evertor muscles and on the second day in a fatigued state. Tests included static posturography on a force platform in a bipedal stance with eyes open and closed and in one-legged support with eyes open and functional jump tests (figure-of-8, side hop, 6-m crossover hop, and square hop). Fatigue of the ankle invertor and evertor muscles was induced using isokinetic dynamometry with 30 repetitions at 120°/s. ResultsParticipants had an average age of 24.3 years (SD ± 2.08), the height of 1.73 m (SD ± 0.08), and a weight of 68.63 kg (SD ± 10.29). The average Body Mass Index (BMI) was 22.88 (SD ± 2.46). A decrease in performance was observed in functional activities and postural control under all conditions after the induction of muscle fatigue, except for the speed at a bipedal stance with eyes open. ConclusionsFunctional jump tests are low cost and useful for clinical practice and evaluation of the effects of muscle fatigue and could be used in clinical practice.

Isokinetic ankle muscle strength is reduced in recreational runners with medial tibial stress syndrome and is not associated with pain

Aim: The purpose of this study was to investigate the strength and ratios of the plantar flexors and ankle dorsiflexors in recreational runners with medial tibial stress syndrome and to assess the association between muscle strength and the level of pain in this population. Methods: Two groups (control and medial tibial stress syndrome) of eighteen runners each participated in this cross-sectional study. Isokinetic dynamometry was used to evaluate muscle strength, and for the analysis, the normalized isokinetic peak torque controlled by gender was used. Results: The medial tibial stress syndrome group showed lower normalized isokinetic peak torque in the dorsiflexors in the concentric (p = 0.008) eccentric (p = 0.011) contraction, as well as a lower plantar flexor, normalized isokinetic peak torque in the concentric (p = 0.001) and eccentric (p = 0.02) when compared to the control group. However, there was no difference in the normalized isokinetic peak torque ratio representative of the stance (p = 0.62) and swing phase (p = 0.16), and the level of pain was not correlated with the strength concentric (p = 0.32) and eccentric (p = 0.621) of plantar flexors, nor to the concentric (p = 0.21) and eccentric of dorsiflexors (p = 0.54). Conclusion: Recreational runners with MTSS showed decreased muscle strength in the sagittal plane of the ankle, no correlation with the level of pain, and no changing the ratio between plantar flexors and dorsiflexors.

Is 12 months enough to reach function after athletes’ ACL reconstruction: a prospective longitudinal study

ContextAnterior Cruciate Ligament (ACL) injury is disabling in several sports because it causes knee instability and functional deficit. Usually, surgical treatments produce the best functional outcomes, however, sometimes they are not always able to fully restore stability and function. ObjectiveThe objective of this study was to evaluate postural balance, muscle strength, and functional performance of young athletes with an ACL injury before and after ACL reconstruction. DesignThis was a longitudinal observational prospective study. Method74 athletes, 60 men, and 14 women, aged between 16 and 45, divided into two groups: the Group-Lesion of ACL with 34 athletes (24.1 years) and the Group-Control with 40 athletes without ACL lesion (27.7 years old). All volunteers performed posturography, isokinetic dynamometry, and the Hop-Test. The ACL-Group was evaluated before and 12 months after the reconstruction and the control group was evaluated once. ResultsThe Postoperative ACL Group presented greater limb symmetry, 0.96 (± 0.12), than the preoperative ACL Group, 0.87 (± 0.17), p < 0.01 in the Hop-Test. In the posturography, the displacement area was smaller in the postoperative ACL Group, 19.85 (± 5.74), compared to the preoperative ACL Group, 24.20 (± 8.97), p < 0.01. In isokinetic dynamometry the torque peak was greater in the postoperative ACL Group, 0.91 (± 0.14), than in the preoperative ACL Group, 0.74 (± 0.15), p < 0.01. ConclusionThe functional outcomes increased in ACL reconstruction athletes after 12 months, but not at the same level as in the Control Group. The result indicates an incomplete functional recovery, adaptive changes in postural control after injury, reconstruction, and return to sport.

Agreement between isokinetic eccentric hamstring strength, Nordic hamstring strength and Nordic break-point angle in a sample of trained and healthy individuals

ABSTRACT Different eccentric strength assessments are used to identifying the risk of hamstring injury in athletes. However, there is scarce information to determine the association between Nordic-based measurements and the gold standard measurement of eccentric hamstring strength in an isokinetic dynamometer. To investigate the relationship of different measures of eccentric hamstring strength (break-point angle and eccentric strength during Nordic exercise) with eccentric hamstring peak torque measured with an isokinetic dynamometer. Forty-six participants volunteered to participate in this study. Eccentric peak force in the Smart-Nordic System and break-point angle measured as trunk lowering at >20°/s and >150°/s2 during the Nordic exercise via high-frequency video-analysis were compared to eccentric hamstring peak torque in an isokinetic dynamometer set to produce knee extension at 30°/s. There was a moderate association between peak eccentric strength with the Smart-Nordic and isokinetic eccentric hamstring peak torque (r = −0.65, p < 0.001, 95%CI = [−0.76-(−0.50)]). The association between Nordic break-point angle measured at 20°/s (r = 0.49, p < 0.001, 95%CI = [0.30–0.64]) and at 150°/s2 (r = 0.52, p < 0.001, 95%CI = [0.33–0.66]) presented statistically significant but lower associations with isokinetic eccentric hamstring peak torque. All Nordic-based measurements presented acceptable associations with the gold standard isokinetic eccentric hamstring peak torque. However, peak eccentric force measured on the Smart-Nordic device had a better agreement with eccentric peak torque measured with an isokinetic dynamometer than the video-based measurements. Highlights Peak eccentric force measured on the isometric strain-gauges device had a better agreement with eccentric hamstring peak torque measured with an isokinetic dynamometer than the break-point angle. The Nordic-based measurements are an alternative cost-effective method to assess eccentric muscle strength and weakness when the access to isokinetic dynamometry is not feasible. Caution should be taken with certain variables such as participants body mass, hip position and movement speed when interpreting the results of Nordic-based measurements.

Omega-3 supplementation during unilateral resistance exercise training in older women: A within subject and double-blind placebo-controlled trial.

SummaryBackground & aimsThe skeletal muscle anabolic effects of n-3 polyunsaturated fatty acids (n-3 PUFA) appear favoured towards women; a property that could be exploited in older women who typically exhibit poor muscle growth responses to resistance exercise training (RET). Here we sought to generate novel insights into the efficacy and mechanisms of n-3 PUFA alongside short-term RET in older women.MethodsWe recruited 16 healthy older women (Placebo n = 8 (PLA): 67±1y, n-3 PUFA n = 8: 64±1y) to a randomised double-blind placebo-controlled trial (n-3 PUFA; 3680 mg/day versus PLA) of 6 weeks fully-supervised progressive unilateral RET (i.e. 6 × 8 reps, 75% 1-RM, 3/wk−1). Strength was assessed by knee extensor 1-RM and isokinetic dynamometry ∼ every 10 d. Thigh fat free mass (TFFM) was measured by DXA at 0/3/6 weeks. Bilateral vastus lateralis (VL) biopsies at 0/2/4/6 weeks with deuterium oxide (D2O) dosing were used to determine MPS responses for 0–2 and 4–6 weeks. Further, fibre cross sectional area (CSA), myonuclei number and satellite cell (SC) number were assessed, alongside muscle anabolic/catabolic signalling via immunoblotting.ResultsRET increased 1-RM equally in the trained leg of both groups (+23 ± 5% n-3 PUFA vs. +25 ± 5% PLA (both P < 0.01)) with no significant increase in maximum voluntary contraction (MVC) (+10 ± 6% n-3 PUFA vs. +13 ± 5% PLA). Only the n-3 PUFA group increased TFFM (3774 ± 158 g to 3961 ± 151 g n-3 PUFA (P < 0.05) vs. 3406 ± 201 g to 3561 ± 170 PLA) and type II fibre CSA (3097 ± 339 μm2 to 4329 ± 264 μm2 n-3 PUFA (P < 0.05) vs. 2520 ± 316 μm2 to 3467 ± 303 μm2 in PL) with RET. Myonuclei number increased equally in n-3 PUFA and PLA in both type I and type II fibres, with no change in SC number. N-3 PUFA had no added benefit on muscle protein synthesis (MPS), however, during weeks 4–6 of RET, absolute synthesis rates (ASR) displayed a trend to increase with n-3 PUFA only (5.6 ± 0.3 g d−1 to 7.1 ± 0.5 g d−1 n-3 PUFA (P = 0.09) vs. 5.5 ± 0.5 g d−1 to 6.5 ± 0.5 g d−1 PLA). Further, the n-3 PUFA group displayed greater 4EBP1 activation after acute RE at 6 weeks.Conclusionn3-PUFA enhanced RET gains in muscle mass through type II fibre hypertrophy, with data suggesting a role for MPS rather than via SC recruitment. As such, the present study adds to a literature base illustrating the apparent enhancement of muscle hypertrophy with RET in older women fed adjuvant n3-PUFA.

Muscle mass, strength, bone mineral density and vascular function in middle-aged people living with HIV vs. age-matched and older controls

IntroductionCombination antiretroviral therapy (cART) substantially extended the life of people living with HIV (PLHIV). However, prolonged HIV infection and cART increase the risk of comorbidities accelerating age-related muscle, bone, and vascular disorders. This cross-sectional study compared muscle mass and strength, bone mineral density (BMD), and vascular function in middle-aged PLHIV treated with cART vs. non-infected age-matched and older controls. MethodsAfter careful screening for secondary diseases and medications, body composition, muscular and vascular function were assessed in 12 PLHIV (43.9±8.7 yrs old; HIV-infection for 16.2±8.6 yrs; on cART for 11.6±9.2 yrs), 12 age-matched (CONT, 43.2±8.5 yrs old), and 12 older (OLDER, 74.4±8.3 yrs old) controls through dual x-ray absorptiometry, isokinetic dynamometry, and venous occlusion plethysmography, respectively. ResultsPLHIV and CONT showed similar relative muscle mass (65.3±8.0 vs. 66.9±7.3%, respectively; P= 0.88) and strength (160.7±53.9 vs. 152.0±52.9 N.m−1, respectively; P= 0.90), which were greater than OLDER (80.6±18.8 N.m−1; P= 0.001). Total BMD was similar in PLHIV (1.04±0.13 g.cm−2) and OLDER (1.00±0.15 g.cm−2, P= 0.86), and both groups presented lower values than CONT (1.20±0.13 g.cm−2, P< 0.01). No significant difference across groups was detected for macrovascular reactivity (P= 0.32). ConclusionAge-related osteopenia might be accelerated in middle-aged PLHIV on prolonged cART, as their BMD approached values found in older adults. On the other hand, muscle mass, isokinetic strength, and vasodilation capacity were similar in PLHIV and age-matched uninfected controls.