Concentric Muscle Strength Research Articles

Effects of different vibration frequencies on muscle strength, bone turnover and walking endurance in chronic stroke

This randomized controlled trial aimed to evaluate the effects of different whole body vibration (WBV) frequencies on concentric and eccentric leg muscle strength, bone turnover and walking endurance after stroke. The study involved eighty-four individuals with chronic stroke (mean age = 59.7 years, SD = 6.5) with mild to moderate motor impairment (Fugl-Meyer Assessment lower limb motor score: mean = 24.0, SD = 3.5) randomly assigned to either a 20 Hz or 30 Hz WBV intervention program. Both programs involved 3 training sessions per week for 8 weeks. Isokinetic knee concentric and eccentric extension strength, serum level of cross-linked N-telopeptides of type I collagen (NTx), and walking endurance (6-min walk test; 6MWT) were assessed at baseline and post-intervention. An intention-to-treat analysis revealed a significant time effect for all muscle strength outcomes and NTx, but not for 6MWT. The time-by-group interaction was only significant for the paretic eccentric knee extensor work, with a medium effect size (0.44; 95% CI: 0.01, 0.87). Both WBV protocols were effective in improving leg muscle strength and reducing bone resorption. Comparatively greater improvement in paretic eccentric leg strength was observed for the 30 Hz protocol.

Acute Hamstring Muscle Tears in Climbers—Current Rehabilitation Concepts

Acute hamstring injuries are often caused by the heel hook technique. This technique is unique to climbing and causes injury to muscular and inert tissues of the posterior thigh. The heel hook is used by climbers during strenuous ascent on overhanging walls and when crossing difficult terrain. The technique reduces the amount of upper body strength required during strenuous climbing because the climber's center of mass is retained within the base of support. The heel hook is stressful collectively for the hamstring muscle group and musculotendinous junction. Depending on injury severity, both conservative and surgical methods exist for the management of hamstring injuries. Contemporary approaches to rehabilitation primarily advocate the use of eccentric muscle strengthening strategies because of high rates of elongation stress associated with sprinting and team sports. However, there is reason to doubt whether this alone is sufficient to rehabilitate the climbing athlete in light of the high degree of concentric muscle strength required in the heel hook maneuver. This review examines the contemporary rehabilitation and strength and conditioning literature in relation to the management of acute hamstring musculotendinous injuries for the climbing athlete. The review provides a comprehensive approach for the rehabilitation and athletic preparation of the climbing athlete from the initial injury to full return to sports participation.

Muscle strength, not age, explains unique variance in echo intensity.

We sought to determine whether EI is more strongly associated with age or strength. Twenty-eight younger adults (13 men, 15 women; mean age=22years) and 25 older adults (10 men, 15 women; age=71years) participated. B-mode ultrasonography was utilized to acquire images of the vastus lateralis and rectus femoris. ImageJ software was used to quantify corrected EI and muscle cross-sectional area (CSA). Each participant performed 40 maximal concentric isokinetic muscle actions of the knee extensors (velocity=180°·s-1). The mean peak torque of the best three attempts was used to quantify muscle strength. Specific torque was calculated as strength relative to CSA. Fatigability was also quantified. Statistical analyses included independent samples t-tests and stepwise regression. There were large differences between age groups for strength (p<.001, d=1.831) and CSA (p=.003, d=0.872). When corrected for subcutaneous tissue thickness, the difference in EI between age groups was small (p=.184, d=0.371). Stepwise regression revealed that muscle strength was the single best predictor of EI (R2=0.206), with age, CSA, specific torque, and fatigability explaining no unique variance. Concentric isokinetic muscle strength is a better predictor of EI than age.

JOINT-, CONTRACTION-TYPE, AND CONTRACTION-VELOCITY SPECIFIC DIFFERENCES IN MUSCLE STRENGTH OF LOWER EXTREMITY IN CHILDREN

PURPOSE: Concentric and eccentric muscle contractions produce dynamic movements requisite for activities of daily living (e.g. walking, running, and jumping). The purpose of this study is to examine joint-, contraction-type, and contraction-velocity specific differences as a function of lower extremity muscle strength in children. METHODS: Thirteen children (male = 5, female = 8; age = 11.2 ± 1.1 years) participated in our cross-sectional study. After a familiarization session, participants performed randomized unilateral isometric (ISO), concentric (CON) and eccentric (ECC) muscle strength testing of the non-dominant knee extensors and ankle plantarflexors in a seated position at 120°/s and 180°/s on Biodex. Obtained peak torques were normalized to body mass. Differential muscle strengths were also calculated [D1 = (ECC120-CON120)knee; D2 = (ECC120-CON120)ankle; D3 = (ECC180-CON180)knee; D4 = (ECC180-CON180)ankle]. We used separate within repeated measures ANOVA to calculate muscle strength differences. Paired t-tests were used to compare the differential muscle strength (D1vs D2; D3 vs D4). RESULTS: No difference was noted between ISO and CON. However, ISO and CON were lower than ECC muscle strength at 120°/s and 180°/s ( P < 0.01) at the knee and ankle. No difference was noted between D1 and D2 but D4 was significantly lower than D3 (P = 0.009). CONCLUSION: Irrespective of contraction velocity and the body sites, children display greatest muscle strength for ECC relative to CON or ISO which is site-dependent. Whether this is dictated by maturation associated site-specific neuromuscular inhibition remains to be investigated.

Effects of Kinesio tape application to trunk isokinetic strength in female participants

ABSTRACT The purpose of this study is to analyse the effects of KT on trunk strength with respect to different angular speeds when applied to the trunks of healthy women. Forty healthy female participants were randomly distributed into two groups: the placebo group (PG) in which placebo KT was applied and the experimental group (EG). Participants’ trunk concentric flexion and extension muscle strength were measured using an isokinetic dynamometer in two different angular speeds (60°/s − 180°/s). In both PG and EG groups, there was no significant difference measured immediately after taping at the two angular speed values. In the measurements taken 48 h later, as regards PG trunk flexion, extension muscle strength increased significantly (p = 0.0001) at 60°/sc. angular speed while, for the EG only, the strength of trunk extension muscle increased significantly (p = 0.002). It was observed, that to ensure an increase in strength, waiting for a certain length of time was required. Lower angular speeds and short-term applied KT improved the strength of the trunk extension muscle.

Maximal oxygen uptake and concentric isokinetic muscle strength in pubertal football trained and untrained boys of the same biological age

The purpose of the present study was to examine the effects of long term (prolonged) football training on maximal oxygen uptake (VO2) and isokinetic muscle strength in young football players and untrained boys of the same biological age. Twenty football competitive boys (mean age 14 ± 0 yrs; height 165.5 ± 8.5 cm; weight 59.9 ± 9.5 kg; years of training 7 ± 3) and eighteen untrained school boys (mean age 14 ± 0; height 168.22 ± 10.46 cm; weight 59.3 ± 9.9 kg) of the same biological age volunteered to participate in the study. Sexual maturation classified according to Tanner’s stage 3. The football players participated both in their school’s physical education program and in their football team training program while the untrained group participated only in their school’s physical education program (2–3 times per week for 40 min). All subjects were tested for maximal oxygen uptake (VO2) and respiratory exchange ratio (RER) on the treadmill using an open circuit spirometry. The isokinetic peak torque values of quadriceps (Q) and hamstrings (H) as well as the H : Q strength ratios were recorded. Hcon : Qcon was calculated as the ratio of the peak concentric torque of H to the peak concentric torque of the Q. Results showed that the trained group had significantly lower heart rate in rest (p < 0.001), higher RER (p < 0.001), maximal blood lactate (BLmax) (p < 0.001) and higher VO2 max in both relative and absolute values (p < 0.001) compared to the untrained group. At angular velocities of 60 ° s−1 and 180 ° s−1 the relative peak torque of Q and H were significantly higher (Q = p < 0.01; H = p < 0.01). However, the absolute values of Q and H as well as the H : Q ratios at all angular velocities did not differ significantly between the two groups. The results suggest that systematic football training (intensity and duration) has a positive effect in metabolic capacity, cardiorespiratory system and neuromuscular function.

Velocity-specific knee strength between professional and under-17 female volleyball players.

BackgroundMany studies have investigated isokinetic performance in volleyball players but not through surface maps.ObjectivesThe goals of this study were to assess velocity-specific isokinetic knee extensor–flexor muscle strength and to compare the isokinetic knee extensor–flexor muscles between professional (PRO) and under-17 (U17) female volleyball players.MethodThis cross-sectional laboratory study was developed with two groups: PRO (n = 12), medianage = 21.3 years, and U17 (n = 9), medianage = 15 years. Peak torque, total work, mean power, angle of peak torque, hamstring–quadriceps torque ratio (H–Q ratio) and torque–angle–velocity surface maps were analysed from knee extension–flexion at 60, 120 and 300 degrees per second (°/s).ResultsSignificant differences were identified for extensor peak torque between PRO x = 202.3 Newton metre (N·m) (standard deviation [SD] = 24.4) and U17 x = 141.6 N·m (30.1) at 60 °/s (p < 0.001; d = 2.21) as well as flexor peak torque (PRO x = 75.7 N·m [10.3] and U17 x = 57.7 N·m [11.4]) at 120 °/s (p < 0.001; d = 1.65) for the dominant limb. There were also significant group differences for total work and mean power at all velocities for extension and flexion. Surface maps demonstrated higher torque at lower speeds for both groups with smaller torque changes across velocities for flexion.ConclusionDifferent groups of female volleyball players showed contrasting concentric knee muscle strength across isokinetic velocities.Clinical implicationsThese results demonstrate the importance of specific strength training for different age groups, even within the same sport, and provide insight into muscle strength.

Effects of the FIFA 11+ on ankle evertors latency time and knee muscle strength in amateur futsal players

Background: The FIFA 11+ has shown to increase muscle strength and reduce injury risk. The purpose of this study was to assess the short and long-term effects of the FIFA 11+ on knee strength, and muscle latency after sudden inversion of amateur futsal players. Methods: Seventy-one male futsal players were recruited and randomized to a FIFA 11+ (n = 37, age: 27.0 ± 5.1 years) and a control group (n = 34, age: 26.0 ± 5.1 years). The FIFA 11+ programme was executed twice a week, for 10 weeks, followed-up after 10 weeks where both groups executed regular warm-ups. Concentric and eccentric isokinetic knee muscle strength was tested and latency time of the evertor muscles after sudden inversion of the ankle was executed with a trapdoor mechanism following an EMG protocol of selected leg muscles (peroneus brevis and peroneus longus). Results: No significant difference were observed between groups for short-term changes in isokinetic strength after adjustment for baseline differences. At long-term, significant gains were obtained after adjustment for baseline differences in eccentric strength for both lower limbs as for the H/Q ratios for the dominant limb. No changes between groups were observed in the peroneus brevis and peroneus longus latency time. Conclusions: Performing FIFA 11+ did not have short-term effects on knee strength and muscle latency after sudden inversion in amateur futsal players. However, significant long-term benefits were observed for eccentric strength and H/Q ratios.

Are People With Joint Hypermobility Syndrome Slow to Strengthen?

ObjectivesTo investigate whether the rate of change of muscle strength in people with joint hypermobility syndrome (JHS) who have anterior knee pain (AKP) differs when compared to 2 control groups who have AKP and to evaluate the relationship between strength and pain as well as the effect of strength upon activity and knee function. DesignA cohort study, with 3 groups: JHS with AKP, generalized joint hypermobility with AKP (GJH), and normal flexibility with AKP (control group [CG]). Follow-up appointments were performed every 2 weeks for 16 weeks. SettingThe physiotherapy outpatient department within a London (United Kingdom) hospital. ParticipantsA total of 102 people, aged between 18 and 55 years, were recruited between July 2014 and March 2016; 47 JHS, 29 GJH, and 26 CG (N=102). After 16 weeks, 31, 20, and 21 participants completed the study, respectively. Participants were recruited from support groups, a London hospital group and university, local sports centers, and clubs. InterventionsIndividualized leg exercises for 16 weeks. Main Outcome MeasureMuscle torque generated from the lower limb, every 2 weeks for 16 weeks. ResultsThere was no difference in the rate of change of concentric muscle strength between the JHS group and the CG or GJH group (P>.88 and P>.97). There was no difference in the rate of change of eccentric muscle strength between the JHS group and the CG or GJH group (P>.60 and P>.94). However, people with JHS were significantly weaker than the other 2 groups, taking 3 to 4 months to reach the baseline strength of the GJH group. ConclusionPeople with JHS can strengthen at the same rate as other people in pain.

Effects of Recreational Ski Mountaineering on Cumulative Muscle Fatigue - A Longitudinal Trial.

Sport is known to have many positive effects on mental and physical health. High-intensity exercise is considered to decrease muscle strength and induce muscle fatigue, which is associated with a higher risk of injury. In recreational alpine skiers, a decrease of eccentric peak hamstring torque, as an indication of muscle fatigue, occurs even after 1 day of skiing. The popularity of ski mountaineering is increasing enormously, but no studies are available on its effects on muscle strength. Therefore, the present study examined the consequences of ski mountaineering on muscle fatigue of the concentric/eccentric quadriceps and/or hamstrings. In addition, a possible role of myofascial foam rolling in reducing muscle fatigue was evaluated. Fifty recreational ski mountaineers (27 males, 23 females) completed five consecutive tours of ski mountaineering within 1 week. After each day of skiing, participants underwent an isokinetic muscle test assessing the concentric and eccentric muscle strength of both thighs. One group completed an additional session of myofascial foam rolling. Right and left concentric quadriceps peak torque, left hamstrings peak torque, left eccentric quadriceps peak torque, as well as right and left hamstring peak torque, were reduced after a single day of ski mountaineering (p ≤ 0.016 for all). However, no cumulative muscle fatigue was detected and we could not demonstrate any effect of myofascial foam rolling. The results show conclusively that a single day of ski mountaineering leads to a significant decrease of concentric and eccentric quadriceps and hamstring strength. Therefore, in order to improve muscle strength for the ski mountaineering season, a physical training program including concentric and eccentric methods can be recommended.

The Cut-off Values for the Diagnosis of Hamstring Shortness and Related Factors

Background:Hamstrings are one of the most frequently evaluated muscle groups for flexibility in the lower extremity. Passive and active knee extension angle values are used as an indirect indicator of hamstring flexibility. However, the lack of consensus on the cut-off values leads to the use of inconsistent angle values in determining the hamstring tightness.Aims:To establish the normative and cut-off values of the passive and active knee extension angles for healthy young adults and to determine the associated factors including the quadriceps strength.Study Design:A cross-sectional study.Methods:A total of 123 volunteer university students, aged 18-24 years, who met the inclusion criteria were included in this study. Passive and active knee extension assessments of the subjects were performed. Subsequently, on the next day, both knee extensor concentric muscle strength of the participants was measured in the isokinetic system. The knee extension angles and the knee extensor strength were recorded as the mean values of the right and the left sides.Results:Passive knee extension angles of 17.1°±9.1° and 9.8°±5.7° and active knee extension angles of 17.8°±9.1° and 13.4°±6° were described as normative values in men and women, respectively. The cut-off values for the diagnosis of hamstring shortness were as follows: passive knee extension angle >32.2° for males and >19.2° for females and active knee extension angle >33.0° for males and >23.4° for females. A significant positive correlation was observed between knee extension angles and isokinetic knee extensor muscle strength in all participants. The knee extension angle and hamstring flexibility were not affected by dominance.Conclusion:The knee extension angles of healthy young people seem to be lower than the results currently reported in the literature. There s a positive correlation between knee extension angles and isokinetic knee extensor muscle strength.

Normative Quadriceps and Hamstring Muscle Strength Values for Female, Healthy, Elite Handball and Football Players.

Risberg, MA, Steffen, K, Nilstad, A, Myklebust, G, Kristianslund, E, Moltubakk, MM, and Krosshaug, T. Normative quadriceps and hamstring muscle strength values for female, healthy, elite handball and football players. J Strength Cond Res 32(8): 2314–2323, 2018—This study presents normative values for isokinetic knee extension and flexion muscle strength tests in 350 elite, female, handball (n = 150) and football (n = 200) players. Isokinetic concentric muscle strength tests at 60°·sec−1 were recorded bilaterally using a dynamometer. Peak torque (in Newton meter [N·m]), body mass normalized peak torque (N·m·kg−1), and hamstring to quadriceps ratio (H:Q ratio) for dominant and nondominant legs were recorded. The female elite players were 20.9 ± 4.0 years, started playing at the elite level at the age of 18.2 ± 2.7 years, with a mean of 9.7 ± 2.2 hours of weekly in-season training. Handball players demonstrated greater quadriceps muscle strength compared with football players (11.0%) (p < 0.001), also when normalized to body mass (4.1%) (p = 0.012), but not for weight-adjusted hamstring muscle strength. The H:Q ratio was higher on the dominant compared with the nondominant leg for handball players only (p = 0.012).The H:Q ratio was significantly lower for handball players (0.58) compared with football players (0.60) (p < 0.02). These normative values for isokinetic knee extension and flexion torques of healthy, elite, female handball and football players can be used to set rehabilitation goals for muscle strength after injury and enable comparison with uninjured legs. Significantly greater quadriceps muscle strength was found for handball players compared with football players, also when normalized to body mass.

Muscle Strength Is a Poor Screening Test for Predicting Lower Extremity Injuries in Professional Male Soccer Players: A 2-Year Prospective Cohort Study

Background: Lower extremity muscle strength tests are commonly used to screen for injury risk in professional soccer. However, there is limited evidence on the ability of such tests in predicting future injuries. Purpose: To examine the association between hip and thigh muscle strength and the risk of lower extremity injuries in professional male soccer players. Study Design: Case-control study; Level of evidence, 3. Methods: Professional male soccer players from 14 teams in Qatar underwent a comprehensive strength assessment at the beginning of the 2013/2014 and 2014/2015 seasons. Testing consisted of concentric and eccentric quadriceps and hamstring isokinetic peak torques, eccentric hip adduction and abduction forces, and bilateral isometric adductor force (squeeze test at 45°). Time-loss injuries and exposure in training and matches were registered prospectively by club medical staff throughout each season. Univariate and multivariate Cox regression analyses were used to calculate hazard ratios (HRs) with 95% CIs. Results: In total, 369 players completed all strength tests and had registered injury and exposure data. Of these, 206 players (55.8%) suffered 538 lower extremity injuries during the 2 seasons; acute muscle injuries were the most frequent. Of the 20 strength measures examined, greater quadriceps concentric peak torque at 300 deg/s (HR, 1.005 [95% CI, 1.00-1.01]; P = .037) was the only strength measure identified as significantly associated with a risk of lower extremity injuries in multivariate analysis. Greater quadriceps concentric peak torque at 60 deg/s (HR, 1.004 [95% CI, 1.00-1.01]; P = .026) was associated with the risk of overuse injuries, and greater bilateral adductor strength adjusted for body weight (HR, 0.75 [95% CI, 0.57-0.97; P = .032) was associated with a lower risk for any knee injury. Receiver operating characteristic curve analyses indicated poor predictive ability of the significant strength variables (area under the curve, 0.45-0.56). Conclusion: There was a weak association with the risk of lower extremity injuries for 2 strength variables: greater quadriceps concentric muscle strength at (1) high and (2) low speeds. These associations were too small to identify an “at-risk” player. Therefore, strength testing, as performed in the present study, cannot be recommended as a screening test to predict injuries in professional male soccer.

Shoulder Dynamic Control Ratio and Rotation Range of Motion in Female Junior Elite Handball Players and Controls.

To compare glenohumeral range of motion and shoulder rotator muscle strength in healthy female junior elite handball players and controls. Cross-sectional case-control study. Sports medical center. Forty elite female handball players and 30 controls active in nonoverhead sports participated in this study. Passive external rotator (ER), internal rotator (IR), and total range of motion (TROM) of the dominant and nondominant arm were examined with a goniometer. An isokinetic dynamometer was used to evaluate concentric and eccentric rotator muscle strength at 60 and 120 degrees/s with dynamic control ratio (DCR = ERecc:IRcon) as the main outcome parameter. Except for the ER range of motion in the nondominant arm, no significant differences were found between groups for IR, ER of the dominant arm, and the TROM. Within the handball group, the side-to-side difference for IR of the dominant arm was -1.4 degrees. The ER and the TROM of the dominant arm were significantly larger, 6.3 and 4.9 degrees, respectively. For both groups, the DCR values were above 1 and no significant differences were found between the dominant and nondominant arm. The DCR values in the handball group were significantly lower than in the control group. Based on the adopted definitions for muscle imbalance, glenohumeral internal range of motion deficit and TROM deficit our elite female handball players seem not at risk for shoulder injuries. Prospective studies are needed to support the belief that a DCR below 1 places the shoulder at risk for injury.

INVESTIGATION OF THE RELATIONSHIP BETWEEN ISOKINETIC STRENGTH OF KNEE FLEXOR AND EXTENSOR MUSCLES AND VERTICAL JUMP PERFORMANCE IN ELITE MALE VOLLEYBALL PLAYERS

Aim: The purpose of the study is to determine the relationship between the isokinetic strength of the knee flexor and extensor muscles and vertical jump performance. Method: 28 elite male volleyball players (Xage = 17,56 ± 1,94 years) were included in the study. Squat and countermovement jump heights of the athletes were obtained using the OptoJump® device. At the same time, the isokinetic muscle strength of flexor and extensor muscles of knee joints of volleyball players was measured concentrically and eccentrically with an Isomed 2000® device. In order to examine the relation between variables; Pearson correlation analysis was used. Regression analysis was used in order to determine the levels of predicting dependent variables of the independent variables which were determined to be correlated with each other. Results: According to the regression analysis result, quadriceps muscle strength affects 61% of change in squat splash height and 60% of change in countermovement jump height. Hamstring muscle affects 56% of the change in squat jump height and 59% of the change in active jump height. However, when using segmental analysis, it was determined that concentric strength of the left-sided quadriceps muscle at 60º/sec affected squat jump and countermovement jump performance positively on the weak level. The concentric and eccentric muscle strength of quadriceps muscle at 180º/sec angular velocity affected moderately positively the squat jump and countermovement jump performance. At the same time, the right side eccentric contraction of the hamstring muscle at 60 º /sec velocity was found to be an important predictor of squat jump and countermovement jump. Conclusion: According to the results of the study, it was determined that the concentric and eccentric muscle strength of the quadriceps and hamstring muscles affected both the squat and countermovement performance. We think that to increase the vertical jump performance, the eccentric muscle strength of the right hamstring muscle's and the concentric muscle strength of the left quadriceps muscle at the 60º/sec velocity and the concentric and eccentric muscle strength of the quadriceps muscle of both sides at the 180º / sn angular velocity should be increased.

Knee flexion and extension strength in young Brazilian soccer players: the effect of age and position

PurposeTo compare isokinetic knee flexors and extensors concentric muscle strength in young soccer players of different ages and playing positions.MethodsSeventy-seven young male soccer players were divided into 3 age categories: U-15, U-17, and U-20, with the consideration of 4 game positions: goalkeepers, defenders, midfielders, and forwards. The concentric tests of the hamstrings (Hcon) and quadriceps (Qcon) were performed at 30°/s, 60°/s, and 180°/s, and the ratio of 180°/30° was calculated.ResultsThe values of Qcon for the U-15 turned out significantly lower in comparison with the U-20 in 30°/s and 180°/s and in the 180°/30° ratio. The Hcon values for the U-15 were significantly lower than for the U-20 at 30°/s, 60°/s, 180°/s, as well as in the 180°/30° ratio. Strength levels were shown to be significantly different between the 3 analysed categories. The goalkeepers presented with Qcon and Hcon values significantly higher than the other playing positions, regardless of the angular velocity used.ConclusionsU-15, U-17, and U-20 athletes do not have the same level of strength. The goalkeepers demonstrated high strength values, suggesting the importance of specific training for each game position.

Trunk flexor and extensor muscle performance in chronic stroke patients: a case–control study

BackgroundAlthough chronic stroke patients commonly show impairment of trunk muscle performance, this disability has only been analyzed in terms of peak torque. Therefore, other measures are needed for a more adequate description. ObjectiveThis study aimed to compare concentric muscle performance of trunk flexor/extensor muscles between chronic stroke patients and matched-healthy subjects. Methods18 chronic stroke patients and 18 healthy subjects were matched according to their age, sex, body mass index and level of physical activity. After familiarization, trunk flexor/extensor concentric muscle strength was measured using an isokinetic dynamometer (Biodex Medical Systems Inc, Shirley, NY, USA) with 3 repetitions at a velocity of 60°/s and 5 repetitions at a velocity of 120°/s. Trunk muscular performance was characterized by peak torque, torque at 90°, total work, and total work normalized by trunk mass. Student's t-test was used for independent samples (α=0.05) for group comparisons. ResultsAll trunk muscle performance variables values investigated were significantly lower in chronic stroke patients when compared to matched-healthy subjects (p≤0.001). The obtained ratios of chronic stroke patients scores to that of the matched-healthy subjects at velocities of 60°/s and 120°/s were, respectively: flexor peak torque (60% & 53%)/extensor (54% & 53%); flexor torque at 90° (56.20% & 36.58%)/extensor (57.92% & 30.65%); flexor total muscular work (51.27% & 38.03%)/extensor (47.97% & 39.52%); and flexor total muscular work normalized by trunk mass (55.57% & 40%)/extensor (51.40% & 42%). ConclusionsChronic stroke patients showed decreased trunk muscle performance when compared to matched-healthy subjects in all variables investigated.

EVALUATION OF THE RELATIONSHIP BETWEEN ISOKINETIC STRENGTH AND FIELD PERFORMANCE IN PROFESSIONAL MALE VOLLEYBALL PLAYERS

The purpose of this study was to investigate the relationship between the isokinetic quadriceps and hamstring strength and, sprinting ability, agility and vertical jump performance in male volleyball players. Twenty professional male volleyball players (average age 24.5±1.1 years; mean body height 186.5±5.02 cm; mean body mass 75.34±8.39 kg) participated in this study voluntarily. For each player, isokinetic concentric muscle strength tests were performed at 60°/s and 300°/s, jump performance was evaluated by countermovement jump (CMJ) and squat jump (SJ) tests, sprint ability was determined by single sprint performance (10-30 m), and agility performance was measured using the T drill agility test. There were statistically significant correlation between peak torque of extensor and flexor muscles strength at 60°/s, 300°/s contraction velocities and squat jump, countermovement jump (p 0.05). Moreover, statistically significant relations were found between the performances of athletes in different field tests (p<0.05). This study has shown that isokinetic peak torque of quadriceps and hamstring are significant predictor for field based anaerobic tests, SJ and CMJ, that are similar to the actions made in the game for volleyball players. Article visualizations:

Patellar tendon mechanical properties change with gender, body mass index and quadriceps femoris muscle strength

ObjectiveThe purpose of this study is to assess the effect and correlation of gender, body mass index (BMI) and quadriceps femoris (QF) muscle strength on patellar tendon (PT) thickness and stiffness in healthy sedentary individuals. MethodsThis study was carried out with 67 (36 female, 31 male) healthy sedentary individuals between the ages of 18–44 (28.0 ± 7.5 years). The individuals included in the study were divided into two groups according to their gender and BMI (18.5<BMI<25 and 25<BMI). The body composition was determined with Tanita Body Composition Analyser. PT thickness and stiffness was measured with ACUSON S3000 Ultrasonography Device using 9L4 ultrasonography probe. QF concentric muscle strength of the individuals was measured with Biodex® System 4 Dynamometer at 60°/sec angular speed. ResultsIt was found that PT stiffness was higher in males compared to females (p<0.001). It was found that PT stiffness was lower in obese individuals compared to individuals with normal weight (p = 0.017). A negative and weak correlation was found between BMI and PT stiffness (r = −0.26, p = 0.032), whereas a negative and moderate correlation was found between fat percentage and PT stiffness (r = −0.50, p<0.001). A moderate correlation was found between BMI and PT thickness (r = 0.54, p<0.001). It was found that peak torque at 60°/sec angular speed had a moderate correlation with PT stiffness (r = 0.44, p<0.001) and PT thickness (r = 0.45, p<0.001). ConclusionsPT stiffness is correlated and affected by gender, BMI and QF muscle strength whereas PT thickness is correlated and affected only to BMI and QF muscle strength.

Quantifying Quadriceps Muscle Strength in Patients With ACL Injury, Focal Cartilage Lesions, and Degenerative Meniscus Tears: Differences and Clinical Implications.

Background:Reduced quadriceps strength influences knee function and increases the risk of knee osteoarthritis. Thus, it is of significant clinical relevance to precisely quantify strength deficits in patients with knee injuries.Purpose:To evaluate isokinetic concentric quadriceps muscle strength torque values, assessed both from peak torque and at specific knee flexion joint angles, in patients with anterior cruciate ligament (ACL) injury, focal cartilage lesions, and degenerative meniscus tears.Study Design:Cohort study; Level of evidence, 3.Methods:Data were synthesized from patients included in 3 previously conducted research projects: 2 prospective cohort studies and 1 randomized controlled trial. At the time of inclusion, all patients were candidates for surgery. Isokinetic concentric quadriceps muscle strength measurements (60 deg/s) were performed at baseline (preoperative status) and after a period of progressive supervised exercise therapy (length of rehabilitation period: 5 weeks for ACL injury, 12 weeks for cartilage lesions and degenerative meniscus). Outcome measures were peak torque and torque at specific knee flexion joint angles from 20° to 70°. All patients had unilateral injuries, and side-to-side deficits were calculated. For comparisons between and within groups, we utilized 1-way analysis of variance and paired t tests, respectively.Results:In total, 250 patients were included. At baseline, cartilage patients had the most severe deficit (39.7% ± 24.3%; P < .001). Corresponding numbers for ACL and degenerative meniscus subjects were 21.7% (±13.2%) and 20.7% (±16.3%), respectively. At retest, there was significant improvement in all groups (P < .001), with remaining deficits of 24.7% (±18.5%) for cartilage, 16.8% (±13.9%) for ACL, and 3.3% (±17.8%) for degenerative meniscus. Peak torque was consistently measured at 60° of knee flexion, whereas the largest mean deficits were measured at 30° at baseline and 70° at retest for the ACL group, at 70° at baseline and retest for the degenerative meniscus group, and at 60° at baseline and at 50° at retest for the cartilage group.Conclusion:This study underlines the importance of including torque at specific knee flexion joint angles from isokinetic assessments to identify the most severe quadriceps muscle strength deficits. Furthermore, it confirms the importance of progressive exercise therapy interventions before potential surgery in patients with knee injuries.