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PubMed2003

Quantitative Assessment of Lumbar Paraspinal Muscle Endurance.

OBJECTIVE: To evaluate the reliability and variability of repeated measurements of dynamic and static lumbar muscle endurance. DESIGN AND SETTING: Participants performed an isometric lumbar-extension strength test followed by 2 trials of 4 separate lumbar muscular-endurance tests (with a 24-hour rest period between tests). Data were collected at a university musculoskeletal research laboratory. SUBJECTS: Eight healthy, physically active volunteers (5 men, 3 women; age = 25.9 +/- 4.3 years; height = 169.0 +/- 4.6 cm; mass = 73.9 +/- 33.1 kg) participated in this investigation. MEASUREMENTS: We initially tested each participant's isometric lumbar-extension peak torque on a lumbar-extension dynamometer. Static (holding time) and dynamic (repetitions) lumbar-endurance tests were subsequently performed on the lumbar-extension dynamometer and a horizontal roman chair. RESULTS: Interclass reliability was high for all endurance tests completed (r = 0.91 to 0.96, P </=.05). Variability (expressed as total error) for the static-dynamometer and roman-chair tests was 18.3 and 11.6 seconds, respectively, with 2.8 and 1.6 repetitions for the dynamic-dynamometer and roman-chair tests, respectively. CONCLUSIONS: Lumbar muscle endurance can be reliably assessed by both static and dynamic protocols on high- and low-technology devices.

Journal Article↗
PubMed2006

Submaximal aerobic exercise with mechanical vibrations improves the functional status of patients with chronic fatigue syndrome.

AIM: Chronic fatigue syndrome (CFS) is an illness characterised by disabling fatigue of uncertain aetiology and other nonspecific symptoms. Typically CFS patients complain of a severe fatigue made worse by exercise, with a consistent reduction of working activity. A physical deconditioning could explain CFS features as well as a neuromuscular dysfunction, of central or peripheric origin. METHODS: Ten CFS patients were enrolled in a protocol of a rehabilitative treatment over a six-month period: they underwent a submaximal and predominantly aerobic exercise with a reduced O2 consumption using a Galileo 2000 system that provides mechanical vibrations characterised by sinusoid vertical sollecitations. Before and after such treatment, all patients underwent a pressure pain thresholds profile, an evaluation of physical and psychosocial parameters using the visual analogue scale (VAS) of Scott-Huskisson, and a muscle performance analysis by the CIBEX 6000 dynamometer. RESULTS: After the six-month period of study there was an overall improvement of the above described parameters as compared to the basal determinations. CONCLUSION: We conclude that the rehabilitative exertion provides an useful treatment for CFS patients particularly to realize an effective training of the explosive strength.

Adult↗
PubMed1993

Grip strength and hand position of the dynamometer in 204 Finnish adults.

A primary purpose of this study was to establish data on hand strength by Jamar dynamometer for normal Finnish adults aged 30 to 50 years. A second aim was to find out how five various breadths of grip affect the strength value. A sample of 103 male and 101 female adults, aged 19 to 62, from the southern part of Finland were tested using standardized positioning and instructions. Male and female subjects reached the highest grip strength using the third handle breadth of dynamometer, except females over 50 years. Female grip strength was 60% to 70% less than male grip strength. There was no significant difference in strength between dominant and non-dominant hands.

Adult↗
PubMed2000

Caffeine potentiates low frequency skeletal muscle force in habitual and nonhabitual caffeine consumers.

The mechanism of action underlying the ergogenic effect of caffeine is still unclear. Caffeine increases the force of muscular contraction during low-frequency stimulation by potentiating calcium release from the sarcoplasmic reticulum. Studies have also suggested an enhancement of lipid oxidation and glycogen sparing as potential mechanisms. Given that several studies have found an ergogenic effect of caffeine with no apparent metabolic effects, it is likely that a direct effect upon muscle is important. Twelve healthy male subjects were classified as habitual (n = 6) or nonhabitual (n = 6) caffeine consumers based on a 4-day diet record analysis, with a mean caffeine consumption of 771 and 14 mg/day for each group, respectively. Subjects were randomly allocated to receive caffeine (6 mg/kg) and placebo (citrate) in a double-blind, cross-over fashion approximately 100 min before a 2-min tetanic stimulation of the common peroneal nerve in a custom-made dynamometer (2 trials each of 20 and 40 Hz). Tetanic torque was measured every 30 s during and at 1, 5, and 15 min after the stimulation protocol. Maximal voluntary contraction strength and peak twitch torque were measured before and after the stimulation protocol. Caffeine potentiated the force of contraction during the final minute of the 20-Hz stimulation (P<0.05) with no effect of habituation. There was no effect of caffeine on 40-Hz stimulation strength nor was there an effect on maximal voluntary contraction or peak twitch torque. These data support the hypothesis that some of the ergogenic effect of caffeine in endurance exercise performance occurs directly at the skeletal muscle level.

Adult↗
PubMed2005

Relationship between muscle strength in various isokinetic movements and kick performance among soccer players.

AIM: The present study was carried out to examine relationships between muscular strength and ball velocity with respect to 3 different approach angles and focussing on both the kicking leg and the supporting leg among soccer players of different skill levels. METHODS: Fourteen university soccer players were divided into 2 groups (superior group, average group), and kicked the ball with maximal effort towards a target 15 m away. The angles of approach to the stationary ball varied in 3 directions (free, 1.57, 2.36 rad to the kick direction). Mean ball velocity and the success rate of striking the target with the ball were measured. Maximal isokinetic and concentric muscular strength was measured in terms of motions of the knee Ext/Flex, hip Ext/Flex and hip Abd/Add using an isokinetic dynamometer. RESULTS: The mean ball velocity at free and 1.57 rad approach angles related significantly with hip Add but not with knee Ext strength for the kicking leg. In contrast, the ball velocity at an approach angle of 2.36 rad significantly correlated with knee Ext and hip Flex of the kicking leg. Although ball velocity at the free and the 1.57 rad approach angles showed no relation to strength of the supporting leg, the ball velocity at the 2.36 rad approach angle showed a significant relationship with knee Flex, hip Ext and hip Abd strength of the supporting leg. Furthermore, the superior group had more strength variables related to performance than the average group. CONCLUSIONS: Different approach angles would alter the requirement on muscle strength potential of both kicking and supporting leg during kicking. Especially an angled approach to the kick direction could require greater hip extension and abduction strength on the supporting leg for a higher capability for stabilizing body balance. Besides, skill level may alter the importance of muscle strength requirement to kick performance.

Adult↗
PubMed1986

A computer model of neck muscle endurance and fatigue as a function of helmet loading.

A series of experiments were conducted in which the neck muscles of volunteer subjects were dynamically and statistically loaded by systematic variations of twenty-four headgear configurations consisting of eight different centers-of-gravity (CGs) times three different weights. Six subjects would rotate their heads laterally (from side-to-side) for 30 min with each of the headgear loading combinations. Immediately thereafter, the subject would position his head in an isometric head dynamometer and exert a sustained right lateral neck contraction or forward neck contraction at 70% of his maximum strength, during which endurance time (to fatigue) was recorded. The results indicate that the computer model makes reasonable predictions within the boundary conditions. Input data outside the boundary conditions is rejected. The assumption of insensitivity to vertical loading is demonstrated. The assumption of bilateral symmetric response was confirmed for the 1.45 kg and 2.27 kg helmet loads. However, this assumption was not confirmed for the 4.09 kg helmet load. It is concluded from the computer model that aftward, midline loading is the optimal CG location (i.e. maximal endurance) for heavier helmets in the 3-4 km range.

Adult↗
PubMed2004

Reliability of isokinetic ankle inversion- and eversion-strength measurement in neutral foot position, using the Biodex dynamometer.

This study was designed to investigate the intratester and intertester reliability of isokinetic ankle inversion and eversion-strength measurement in neutral foot position in healthy adults using the Biodex dynamometer. Twenty-five men and women performed five maximal concentric contractions at 60 and 180 degrees/s angular velocities. Two physicians tested each subject. The first physician applied the test four times, and the second physician three times. Reliability of peak torque was assessed by calculating the intraclass correlation coefficient (ICC). At both angular velocities, inversion strength was greater than eversion, and when the angular velocity was increased, inversion and eversion strength were decreased, as tested by both physicians. The first measurements of inversion and eversion strength of the first physician were significantly lower than the other measurements (p<0.01). The intratester ICCs for ankle inversion in healthy young adults were highly reliable (ICC 0.92-0.96), and for the eversion values ranged from 0.87 to 0.94. Intertester ICCs for ankle inversion and eversion peak torque values demonstrated a value of 0.95. Isokinetic tests of ankle inversion and eversion strength at 60 and 180 degrees/s angular velocities in neutral foot position for healthy adults are highly reliable with the Biodex dynamometer.

Adult↗
PubMed2000

Hand-grip muscle strength, lean body mass, and plasma proteins as markers of nutritional status in patients with chronic renal failure close to start of dialysis therapy.

We studied 115 patients (69 men, 46 women) with chronic renal failure (CRF) aged younger than 70 years close to the start of dialysis therapy to assess the prevalence of malnutrition and study the relationship between various nutritional parameters in these patients. Nutritional status was classified by means of subjective global assessment. Anthropometric measurements (AMs) were performed, and hand-grip strength (HGS) was measured using the Harpenden dynamometer. Body composition, including lean body mass (LBM), was evaluated by dual-energy x-ray absorptiometry (DXA), and LBM was also estimated by means of AMs and creatinine kinetics (CK). The mean age of the patients was 52 +/- 12 years, and creatinine clearance was 9 +/- 3 mL/min. Malnutrition was seen in 53 patients (48%). As expected, malnourished patients differed in several aspects from well-nourished patients. LBM (estimated by all methods), fat mass (FM), HGS, creatinine clearance, and transthyretin and vitamin A levels were less in malnourished patients, whereas serum albumin levels did not differ. Estimates of LBM by means of DXA, AMs, and CK correlated well with each other. Although DXA and AMs gave similar mean values, LBM was an average of 8 kg less estimated by means of CK, and Bland-Altman plots showed the best agreement between AMs and DXA. HGS showed a strong correlation to LBM (regardless of method) in both men and women. Serum albumin level was not related to HGS or LBM, whereas significant correlations were found between serum albumin level and albumin losses in urine, C-reactive protein (CRP) level, and creatinine clearance. Multiple logistic regression showed that low HGS, low percentage of FM, female sex, and high serum CRP levels were independent factors associated with malnutrition, whereas serum albumin level and percentage of LBM did not reach statistical significance. In conclusion, the present study shows a high prevalence of malnutrition in predialysis patients with CRF and suggests that HGS is a reliable, inexpensive, and easy-to-perform nutritional parameter in patients with CRF. Conversely, serum albumin level seems to be a poor nutritional marker in patients with advanced CRF.

Blood Proteins↗
PubMed1993

The effects of unilateral velocity-specific concentric strength training.

There is conflicting evidence regarding the efficacy of various resistance training programs for increasing strength in trained and contralateral limbs. The purposes of this investigation were to examine the effects of unilateral velocity-specific concentric isokinetic training of the extensor and flexor muscles of the elbow and knee on: 1) the carry-over effect in strength increases to velocities other than the training velocity in the trained limbs and 2) the cross-training effect at various velocities in the contralateral limbs. Twelve adult men (mean age +/- SD = 24 +/- 6 years) volunteered to train their nondominant extremities three times per week (six sets of 10 maximal repetitions) for 8 weeks at 120 degrees/sec using a Cybex II isokinetic dynamometer. The subjects were tested for increases in peak torque at 60, 120, 180, 240, and 300 degrees/sec. The training resulted in significant (p < 0.05) increases in peak torque on the trained side of the body for elbow extension and flexion as well as knee extension and flexion at all velocities tested. These findings indicated that the velocity-specific training resulted in increases in peak torque at velocities that were both greater and less than the training velocity. In addition, there was a cross-training effect, with significant (p < 0.05) increases in peak torque on the contralateral side of the body for elbow extension (all velocities except 300 degrees/sec) as well as knee extension and flexion (all velocities). These results indicate that unilateral velocity-specific concentric isokinetic training is adequate stimulus for eliciting strength gains at a wide range of velocities in both the trained and contralateral limbs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2004

Antioxidants and physical performance in elderly persons: the Invecchiare in Chianti (InCHIANTI) study.

BACKGROUND: Muscle strength and physical performance in old age might be related to the oxidative damage caused by free radicals. OBJECTIVE: The objective was to assess the correlation of plasma concentrations and daily dietary intakes of antioxidants with skeletal muscle strength and physical performance in elderly persons. DESIGN: This study is part of the Invecchiare in Chianti (InCHIANTI) study, which was conducted in 986 Italians aged > or = 65 y. Physical performance was assessed on the basis of walking speed, ability to rise from a chair, and standing balance. Knee extension strength was assessed with a hand-held dynamometer. The European Prospective Investigation into Cancer and Nutrition (EPIC) questionnaire was used to evaluate the daily dietary intakes of vitamin C, vitamin E, beta-carotene, and retinol. Plasma alpha- and gamma-tocopherol concentrations were measured. Adjusted linear regression analyses were used to calculate regression coefficients per SD increase in plasma concentrations and daily dietary intakes. RESULTS: In adjusted analyses, plasma alpha-tocopherol was significantly correlated with knee extension (beta = 0.566, P = 0.003) and the summary physical performance score (beta = 0.044, P = 0.008). Plasma gamma-tocopherol was associated only with knee extension strength (beta = 0.327, P = 0.04). Of the daily dietary intake measures, vitamin C and beta-carotene were significantly correlated with knee extension strength, and vitamin C was significantly associated with physical performance (beta = 0.029, P = 0.04). CONCLUSIONS: Plasma antioxidant concentrations correlate positively with physical performance and strength. Higher dietary intakes of most antioxidants, especially vitamin C, appear to be associated with higher skeletal muscular strength in elderly persons.

Aged↗
PubMed2006

A 2-year follow-up study on muscle size and dynamic strength in teenage tennis players.

Growth trends in the cross-sectional area of the quadriceps femoris (CSA(QF)) and its dynamic strength in 12 teenage tennis players (six boys and six girls), aged from 10.7 to 13.2 years at the onset of the study, were investigated through a 2-year follow-up survey. CSA(QF) values at the three levels (proximal, mid, and distal to the knee joint) and dynamic torques during knee extensions at three pre-set velocities (1.05, 3.14, and 5.24 rad/s) were determined year by year, i.e., three times (T1, T2, and T3), using magnetic resonance imaging and an isokinetic dynamometer, respectively. In both genders, the CSA(QF) values at the three levels tended to increase across the measurement times, with greater gains in the boys than in the girls at the levels mid and distal to the knee joint. Among these changes, only the CSA(QF) at the level proximal to the knee joint significantly increased regardless of changes in both skeletal age and body height. The ratios of torque to the sum of CSA(QF) at the three levels (T/CSA) at 3.14 and 5.24 rad/s for the boys and at 5.24 rad/s for the girls were significantly higher in T2 and T3 than T1. Further, the relative increases in torque and T/CSA values at 3.14 and 5.24 rad/s were greater in the boys than the girls. The findings presented here indicate that young tennis players who are in the earlier stage of adolescence increase the CSA of the QF muscle beyond normally expected growth change at the level proximal to the knee joint and show a predominant development in torque generation capability during high-velocity knee extensions, with a greater gain in boys compared with girls.

Adolescent↗
PubMed2005

The relationship between ciliary neurotrophic factor (CNTF) genotype and motor unit physiology: preliminary studies.

BACKGROUND: Ciliary neurotrophic factor (CNTF) is important for neuronal and muscle development, and genetic variation in the CNTF gene has been associated with muscle strength. The effect of CNTF on nerve development suggests that CNTF genotype may be associated with force production via its influence on motor unit size and firing patterns. The purpose of this study is to examine whether CNTF genotype differentially affects motor unit activation in the vastus medialis with increasing isometric force during knee extension. RESULTS: Sixty-nine healthy subjects were genotyped for the presence of the G and A (null) alleles in the CNTF gene (n = 57 G/G, 12 G/A). They were tested using a dynamometer during submaximal isometric knee extension contractions that were from 10-50% of their maximal strength. During the contractions, the vastus medialis was studied using surface and intramuscular electromyography with spiked triggered averaging to assess surface-detected motor unit potential (SMUP) area and mean firing rates (mFR) from identified motor units. CNTF genotyping was performed using standard PCR techniques from DNA obtained from leucocytes of whole blood samples. The CNTF G/A genotype was associated with smaller SMUP area motor units and lower mFR at higher force levels, and fewer but larger units at lower force levels than G/G homozygotes. The two groups used motor units with different size and activation characteristics with increasing force generation. While G/G subjects tended to utilize larger motor units with increasing force, G/A subjects showed relatively less increase in size by using relatively larger units at lower force levels. At higher force levels, G/A subjects were able to generate more force per motor unit size suggesting more efficient motor unit function with increasing muscle force. CONCLUSION: Differential motor unit responses were observed between CNTF genotypes at force levels utilized in daily activities.

Adult↗
PubMed1983

Neck muscle loading and fatigue: systematic variation of headgear weight and center-of-gravity.

An extensive series of experiments has been conducted to quantify the fatigue of neck muscles as measured by isometric endurance time. The neck muscles were dynamically and statically loaded by systematic variation of 15 headgear configurations consisting of 5 different centers-of-gravity (forward-low, center-low, center-high, right-lateral-low and afterward-low) and 3 different weights (3.2 lb, 5.0 lb, 9.0 lb, 1.45, 2.27, 4.09 kg). Each of six subjects would rotate his head laterally (from side-to-side) for 30 min in each of the 15 headgear loading combinations. Immediately thereafter, the subject would position his head in an isometric head dynamometer and exert a sustained right lateral neck contraction at 70% of his maximum strength (MVC), during which endurance time (to fatigue) was recorded. The results indicate that there were no significant differences (p greater than 0.05) in endurance time between the 3.2 lb/forward-low, 3.2 lb/lateral-right-low, and 9.0 lb/afterward-low compared to controls (endurance time for at 70% MVC isometric neck contraction in which there was no prior head loading). All other head loading configurations (weight and center-of-gravity combinations) did result in a significant reduction (p less than or equal to 0.05) in endurance times (compared to controls). These results are significant since they provide useful insights into the optimal trade-off between various centers-of-gravity and helmet weight combinations which result in the optimization of neck muscle endurance.

Adult↗
PubMed1998

Long-term loading and regional bone mass of the arm in female volleyball players.

In the present study, we compared the bone mineral content (BMC) and bone mineral density (BMD) in the arms of 11 female volleyball players (mean age 22.0 +/- 2.6 years) training for about 8 hours/week, and 11 nonactive females aged 24.6 +/- 3.1 years (mean +/- SD) not participating in regular or organized sport activity. Using dual X-ray absorptiometry (DXA), BMC was measured in the proximal and distal humerus, and BMD in the distal radius. Isokinetic concentric peak torque (highest value attained during 5 or 10 repetitions) of the rotator muscles of the shoulder and flexor and extensor muscles of the elbow were measured using an isokinetic dynamometer. The volleyball players had significantly higher BMC (P < 0.05) at the proximal humerus of the dominant arm compared with the nonactive group, but there were no differences between the groups in BMC of the distal humerus and BMD of the distal radius. In the volleyball players, BMC was significantly higher at the proximal humerus, at the distal humerus, and at the distal radius in the dominant compared with the nondominant arm. In the nonactive group, there were no significant differences in BMC and BMD between the dominant and nondominant arm at any site measured. Except for shoulder internal rotation strength and elbow flexion strength at 90 degrees/second that was higher in the dominant arm in the volleyball players, there were no significant differences in muscle strength of the rotator muscles of the shoulder and flexor and extensor muscles of the elbow between the dominant and nondominant arm in the volleyball players and nonactive controls. In the volleyball players, but not in the nonactive controls, there were several significant relationships between shoulder and elbow strength and BMC at the distal humerus of the dominant and especially the nondominant arm. These results show that young female volleyball players have a higher bone mass in the proximal humerus, distal humerus, and distal radius in the dominant compared with the nondominant arm, and a higher bone mass in the proximal humerus compared with nonactive controls. Muscle strength of the rotator muscles of the shoulder is not related to the higher bone mass in the proximal humerus of the dominant arm. Theoretically, the observed differences in bone mass can be related to the type of loading the skeleton undergoes when playing volleyball.

Adipose Tissue↗
PubMed1995

Comparative effectiveness of accommodating and weight resistance training modes.

Six men and six women trained the elbow flexors of both arms 3 d.wk-1 for 20 wk. In each training session, one arm did 3-5 sets of 10 maximal concentric actions on an accommodating resistance device (ARD), the other arm 3-5 sets of 8-12 coupled eccentric/concentric actions (repetitions) to volitional failure (8-12 RM) on a weight resistance device (WRD). The average "intensity" (force of concentric actions) was approximately 1.25 times greater in ARD training, the average "volume" (number of actions x force of actions) 1.6 times greater in WRD training, and the time required to complete a training session the same for each. Both types of training produced significant increases in a single maximum weight lift (1 RM on the WRD), in the peak force of a single maximal concentric action measured on the ARD and an isovelocity dynamometer, and in biceps, brachialis, and total elbow flexor cross-sectional area (CSA). Biceps Type I and II fiber area did not change significantly. WRD training produced greater increases than ARD training in the 1 RM test on the WRD and in brachialis CSA. The data indicate that both of these common training regimens effectively increase strength and muscle mass, but the weight training regimen may be more effective for increasing muscle mass.

Adult↗
PubMedDate not supplied

Oral amino acids in elderly subjects: effect on myocardial function and walking capacity.

BACKGROUND: With advancing age the risk of developing serious nutritional deficiencies increases, and disturbances to the actions of insulin and insulin-like growth factor, coupled with reduced protein/amino acid (AA) intake, impair protein synthesis in muscles. OBJECTIVE: To assess the effects of administering oral AAs on walking capacity and perceived walking impairment, isometric muscular strength, and myocardial function at rest and during isometric exercise. METHODS: One hundred elderly subjects (aged >65 years) with reduced physical activity were randomized to receive an oral AA mixture (12 g/day) or placebo for 3 months. At baseline and after 3 months of therapy we assessed physical capacity with the 6-min walk test, and perceived physical impairment with the walking impairment questionnaire (WIQ); we assessed maximal isometric muscular strength of the right hand with a handgrip dynamometer, and left ventricular ejection fraction (LVEF) using quantitative two-dimensional echocardiography at rest and during acute overload. RESULTS: Three months of AA treatment resulted in significant increases in 6-min walk distance (268.8 +/- 34.9 vs. 212 +/- 40 m, p < 0.001), WIQ scores (distance: 68.3 +/- 12 vs. 53 +/- 14.8%, p < 0.001; speed: 72.2 +/- 14.4 vs. 52.8 +/- 12%, p < 0.001; stairs: 98.2 +/- 24 vs. 72.4 +/- 22%, p < 0.001), and in maximal muscular isometric strength (20.2 +/- 2 vs. 14 +/- 2.8 kg, p < 0.001). Moreover, peak stress LVEF was higher during AA administration when compared to placebo administration (67 +/- 7 vs. 56 +/- 9%, p < 0.01). Left ventricular response to exercise normalized during AA administration in 24 out of 32 (75%) patients with abnormal LV response at baseline, whereas it remained unchanged in the placebo group. CONCLUSION: An oral AA supply such as that used in this study improves ambulatory capacity, maximal isometric muscle strength and myocardial ability to match an acute overload in elderly subjects without affecting the main metabolic parameters. These functional gains may translate into increased perceived walking capacity.

Administration, Oral↗
PubMed2001

Relationship between muscle strength and the time taken to complete a standardized walk-turn-walk test.

We examined the effects of age and gender on the relationship between knee strength and walking time during a walk-turn-walk test in 176 male and 168 female generally healthy participants of the Baltimore Longitudinal Study of Aging who were aged 21-89 years. Subjects were timed as they walked 50 ft (15.24 m), turned around, and walked back to the starting point, both at a comfortable pace and as fast as possible. Isokinetic concentric knee extensor strength was measured at 30 degrees /s by using a Kin-Com dynamometer. Both comfortable and fast gait times increased with increasing age for both women and men, starting in middle age. An interaction was found between gender and age showing that older women are slower than older men at both paces. Gait time decreased linearly with increasing knee extensor strength, plateauing at higher strength levels (>130 N m for comfortable gait, and 190 N m for fast gait). Most women occupied the linear part of the curve below the plateau. Adjustment for body size, age, physical activity, and particularly number of steps to complete the task removed the relationship between strength and gait time for the comfortable gait. Women took longer to complete the walk-turn-walk test than men at older ages, were on the linear part of the strength-gait time relationship, and used more steps to complete the task, all of which may contribute to their greater likelihood of frailty in later years.

Adult↗
PubMed1999

Comparison of isokinetic peak force and work parameters in youth with and without mental retardation.

PURPOSE: The purpose of this study was to compare isokinetic knee (flexion and extension) strength of nondisabled youth (ND; 15 males, 15 females; males = 12.7 +/- 2 yr; females = 13.4 +/- 2 yr) and youths with mental retardations (MR, 17 males + 13 females; male = 14.7 +/- 2 yr; females = 13.6 +/- 2 yr). METHODS: Subjects were evaluated on a Kin-Con isokinetic dynamometer at a speed of 60 degrees x s(-1). Parameters measured were peak torque (PT), time to PT, angle of PT, total work (W), and PT hamstrings/quadriceps (HQ) ratio. Peak torque was also corrected by weight (BW) and body mass index (BMI). Peak torque, time to peak torque, angle of peak torque, and total work were analyzed using a 2 x 2 x 2 (groups x gender x muscle) repeated measures analysis of variance (MANOVA). Flexion/extension ratios, BMI, and BW were analyzed by separate 2 x 2 (group x gender) analyses of variance. RESULTS: Results of this study suggest that: 1) while gender differences are apparent in the ND population they are not evident in individuals with MR; 2) knee extension strength is higher for ND youth, thus causing lower PT HQ ratios when compared with those in youth with MR; 3) angle of PT and time to PT were similar among groups; and 4) total work performed is lower in individuals with MR. CONCLUSIONS: It was concluded that parameters of strength production in individuals with MR are not consistent and do not follow the same pattern as their nonretarded peers.

Adolescent↗