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PubMed1995

Isokinetic eccentric exercise.

The development of active isokinetic dynamometers has allowed the assessment of muscular moment under eccentric activations that have different characteristics to concentric actions. It is well documented that at a given angular velocity the eccentric moment is greater than the corresponding concentric moment. The moment-velocity relationship under eccentric conditions has been investigated, with conflicting results. Particularly, eccentric moment was reported to remain similar to, or to increase or decrease with, increasing angular velocity. As with concentric actions, the reliability of isokinetic eccentric measurements is influenced by a number of factors such as gravity, preload force and testing position. The velocity-specific effects of eccentric training have not been extensively investigated. Based on current knowledge, eccentric exercise does not appear to be velocity-specific. Although the mode specificity of both concentric and eccentric exercises have been investigated, the resultant observations are conflicting. Eccentric training has been found to improve both concentric and eccentric strength: yet, it has also been reported to improve only concentric or eccentric strength. The reciprocal muscle group ratios under eccentric actions were found not to be influenced by angular velocity, but the significant role of the eccentric/concentric moment ratio of each muscle has not been examined thoroughly. It is well documented that eccentric activations are associated with delayed muscle soreness and muscle damage. A limited number of studies have reported that isokinetic eccentric efforts may result in a lower amount of muscle soreness compared with other exercise modalities. Isokinetic dynamometers provide some unique characteristics for rehabilitation applications. Examination of the clinical application of eccentric exercise is limited. Consequently, the use of this exercise modality in prevention and assessment of musculoskeletal injuries should be investigated further.

Athletic Injuries↗
PubMed1992

Eccentric and concentric torques of knee and elbow extension in young and older men.

The purpose of this study was to compare the strength of knee extensors and elbow extensors in young and older men under conditions of eccentric loading and concentric contractions. Twelve men ages 23 to 32 years and 12 ages 60 to 75 years were tested at two angular velocities of movement, 90 and 180 degrees.s-1, on a KinCom isokinetic dynamometer. Compared to young men, older men had lower concentric peak torque values for elbow (31%) and knee (32%) extensors (p less than 0.05). The older group showed lower eccentric peak torques on all elbow comparisons (21% lower), and for knee extension at the slower velocity (20%). At the faster velocity, knee extension eccentric peak torque did not differ from that of younger men. Differences between the age groups were significantly less for the eccentric muscle action than for the concentric one. The observation of maintained eccentric strength in older men, particularly at fast velocity, warrants research in defining the mechanism.

Adult↗
PubMed1999

Stretching and strengthening exercises: their effect on three-dimensional scapular kinematics.

OBJECTIVE: To quantitatively evaluate the effects of commonly used shoulder exercises on shoulder kinematics and resting posture. STUDY DESIGN: A repeated-measures design was used with measurements performed before and after a 6-week exercise program. METHOD: Twenty asymptomatic subjects with forward shoulder posture were recruited. Stretching exercises for the pectoral muscles and resisted strengthening exercises for the scapular retractors and elevators and the glenohumeral abductors and external rotators were performed three times per week for 6 weeks. A three-dimensional electromechanical digitizer was used to measure thoracic inclination and scapular orientation and position. These measurements were taken with the arm (1) at the side, (2) abducted to 90 degrees, and (3) at maximal abduction. The isometric force of glenohumeral external and internal rotation and horizontal abduction and adduction were measured with a hand-held dynamometer. All subjects were tested before and after the 6-week exercise program. Hotelling's T2 and paired t tests were used for data analysis. RESULTS: The strength of horizontal abduction and internal and external rotation increased after exercise (p < .01). The anterior inclination of the thoracic spine decreased, and the glenohumeral contribution to arm elevation increased (p < .01). Resting scapular posture did not change. As the arm was abducted to 90 degrees, the scapula showed less upward rotation and less superior translation after the exercise program (p < .01). CONCLUSION: The exercise program improved muscle strength, produced a more erect upper trunk posture, increased scapular stability, and altered scapulohumeral rhythm.

Adult↗
PubMed1995

Response to resistance training in young women and men.

Six women and 6 men trained the elbow flexors 3 days per week for 20 wks, one arm performing in each session 3-5 sets of 10 maximal concentric actions on an accommodating resistance device, the other arm 3-5 sets of 8-12 coupled eccentric/concentric actions on a weight training device. With results collapsed across the two training modes, the women made significantly (p < 0.05) greater relative increases than men in strength measured on the weight (116 vs. 46%) and accommodating (99 vs. 46%) resistance devices, and greater absolute (3.5 vs. -1.3 N.m) and relative (13.7 vs. -3.2%) increases in strength measured on an isokinetic dynamometer. Absolute (cm2) and relative (%) biceps, brachialis, and total elbow flexor cross-sectional area (from CT scans) increased significantly; however, the women's vs. men's respective relative and absolute increases did not differ significantly: biceps (13 vs. 7%, 0.9 vs. 1.0 cm2), brachialis (53 vs. 31%, 2.1 vs. 2.3 cm2), and total (26 vs. 15%, 3.1 vs. 3.3 cm2) flexor area. Biceps type I and II fiber area, and the II/I area ratio did not increase significantly. The data indicate that in response to the same short-term training program, muscle size increases similarly in women and men but women make greater relative increases in strength.

Adult↗
PubMed1995

Role of flexors in knee stability.

The muscle strength of knee extensors is commonly used as an indicator of a patient's functional recovery following reconstruction of the anterior cruciate ligament (ACL). The knee flexors are dynamic stabilizers that prevent tibial anterior displacement and may reinforce the function of the ACL. The purpose of this study was to examine the relationship of knee flexor performance assessed by isokinetic dynamometer and clinical evaluations including KT-1000 stability tests, shuttle run tests, thigh and calf circumference and range of motion of the knee joint. Ten patients who received ACL reconstruction over a 3- to 5-year period were included in this study, as were 15 normal controls who were tested for comparison. There was no significant difference in the time taken for the shuttle run test between normal controls and patients who underwent ACL, but there was a positive correlation between the shuttle run test and laxity of the knee joint. The knee laxity of ACL patients was significantly greater than that of the normal controls under passive anterior force. However, no significant difference was seen in the stability test under active contraction of the knee extensors. In addition, a positive correlation was seen between the KT-1000 knee ligament arthrometry test results and both torque acceleration energy and the average power of the flexors. These results suggest that physical therapy for patients following ACL reconstruction should emphasize the explosiveness of knee flexors to help strengthen the dynamic stability of the knee joint and motor performance.

Adult↗
PubMed2004

Whole-body-vibration training increases knee-extension strength and speed of movement in older women.

OBJECTIVES: To investigate the effects of 24 weeks of whole-body-vibration (WBV) training on knee-extension strength and speed of movement and on counter-movement jump performance in older women. DESIGN: A randomized, controlled trial. SETTING: Exercise Physiology and Biomechanics Laboratory, Leuven, Belgium. PARTICIPANTS: Eighty-nine postmenopausal women, off hormone replacement therapy, aged 58 to 74, were randomly assigned to a WBV group (n=30), a resistance-training group (RES, n=30), or a control group (n=29). INTERVENTION: The WBV group and the RES group trained three times a week for 24 weeks. The WBV group performed unloaded static and dynamic knee-extensor exercises on a vibration platform, which provokes reflexive muscle activity. The RES group trained knee-extensors by performing dynamic leg-press and leg-extension exercises increasing from low (20 repetitions maximum (RM)) to high (8RM) resistance. The control group did not participate in any training. MEASUREMENTS: Pre-, mid- (12 weeks), and post- (24 weeks) isometric strength and dynamic strength of knee extensors were measured using a motor-driven dynamometer. Speed of movement of knee extension was assessed using an external resistance equivalent to 1%, 20%, 40%, and 60% of isometric maximum. Counter-movement jump performance was determined using a contact mat. RESULTS: Isometric and dynamic knee extensor strength increased significantly (P<.001) in the WBV group (mean+/-standard error 15.0+/-2.1% and 16.1+/-3.1%, respectively) and the RES group (18.4+/-2.8% and 13.9+/-2.7%, respectively) after 24 weeks of training, with the training effects not significantly different between the groups (P=.558). Speed of movement of knee extension significantly increased at low resistance (1% or 20% of isometric maximum) in the WBV group only (7.4+/-1.8% and 6.3+/-2.0%, respectively) after 24 weeks of training, with no significant differences in training effect between the WBV and the RES groups (P=.391; P=.142). Counter-movement jump height enhanced significantly (P<.001) in the WBV group (19.4+/-2.8%) and the RES group (12.9+/-2.9%) after 24 weeks of training. Most of the gain in knee-extension strength and speed of movement and in counter-movement jump performance had been realized after 12 weeks of training. CONCLUSION: WBV is a suitable training method and is as efficient as conventional RES training to improve knee-extension strength and speed of movement and counter-movement jump performance in older women. As previously shown in young women, it is suggested that the strength gain in older women is mainly due to the vibration stimulus and not only to the unloaded exercises performed on the WBV platform.

Aged↗
PubMedDate not supplied

Subject variability of shoulder abduction strength testing.

To quantify normal biological variability of shoulder abduction strength testing with an isokinetic and a hand-held dynamometer, we tested nine healthy subjects over a clinically relevant period. One side was tested with a Cybex at 60 deg/sec and the other with a hand-held dynamometer. Six maximal trials, following warmup, were conducted on each of 5 days, separated by 1 to 2 weeks. Intraday correlations of individual trials ranged from 0.82 to 0.995 for hand-held dynamometer, and 0.88 to 0.996 for Cybex. Interday correlations ranged from 0.94 to 0.98 for hand-held dynamometer, and 0.88 to 0.97 for Cybex. The best values to use for Cybex interday variability were the average of the first three repetitions, and yielded standard errors of 8.6% to 19.2% of the sample mean. The average of the last three repetitions were the best for hand-held dynamometers, and yielded standard errors of 5.5% to 10.8%. There was a significant decline (P less than 0.05) in strength of the mean of the last three versus the mean of the first three daily repetitions on Day 1 and 4 for hand-held dynamometers, and a trend toward this on the other days, that was not seen with Cybex. Regression of average Day 1 values for Cybex and hand-held dynamometer yielded r = 0.86 (P less than 0.01) with a slope of 1.07 indicating good agreement between modalities. In conclusion, intraday/interday correlations were high for Cybex and hand-held dynamometer. Interday variability was minimized by using the mean score of the first three and last three repetitions for Cybex and hand-held dynamometer, respectively. Changes in Cybex and hand-held dynamometer strength of less than 19% and 11%, respectively, are within the area of "measurement error" and should therefore not be considered clinically significant.

Adult↗
PubMedDate not supplied

Comparison of muscle strength and flexibility between the preferred and non-preferred leg in English soccer players.

Most soccer players have a favoured foot for kicking the ball, and it is believed that this preference may lead to an asymmetry in the strength and flexibility of the lower extremities. This study was designed to determine whether asymmetry in strength and flexibility are present in the legs of soccer players.Forty-one elite and sub-elite soccer players (age 23.4 +/- 3.8 years; height 1.81 +/- 0.06 m; body mass 81.7 +/- 9.9 kg) were studied (data are presented as mean +/- SD). The dynamic strength of knee flexors (hamstrings) and knee extensors (quadriceps) was measured using an isokinetic dynamometer at angular velocities of 1.05, 2.09, 5.23 rad/s (in a concentric mode) and 2.09 rad/s (in an eccentric mode). The concentric strength ratio (hamstrings(conc)/quadriceps(conc)) and the dynamic control ratio (hamstrings(ecc)/quadriceps(conc)) were computed. Hip joint flexibility (in flexion) was measured using a goniometer.A significant difference between the preferred and non-preferred leg was found in the knee flexors at 2.09 rad/s (119 +/- 22 versus 126 +/- 24 Nm; P < 0.05) and for the dynamic control ratio (0.79 +/- 0.13 versus 0.84 +/- 0.16 Nm; P < 0.05). In both cases the knee flexors of the preferred leg were weaker than those of the non-preferred leg. A total of 28 of the 41 players (68%) had significant musculoskeletal abnormality (imbalance >10%) in one or more specific muscle groups. No significant differences were found in flexibility of the hip joint between the preferred and non-preferred leg (P > 0.05). It is concluded that the lower strength of the knee flexor muscles of the preferred leg may be associated with the differential use of these muscle during the kicking action and thus constitutes a unique training effect associated with soccer. This in turn can lead to muscular imbalance which is generally regarded as an injury risk factor.

Adult↗
PubMed2002

[Feasability of a back school assessment programme].

OBJECTIVES: Testing the feasability of a back school assessment programme in two populations of people suffering with chronic low back pain. MATERIAL: Twenty-nine patients were randomly included in a chronic low back pain assessment programme (15 patients waiting for back school and 14 patients after back school). METHODS: The programme was made of the measure of the age, the sex, the body mass index, the pain (VAS, St Antoine Hospitals Pain Questionnaire - SAPQ), the anxiety, the depression, the RIII nociceptive reflex, the fingertip-floor distance, the strength of the flexors and of the extensors of the lumbar spine (CybexR 6000 isocinetic dynamometer), the lumbar function (EIFEL, Dougados), the Dallas self-questionnaire. The Back School Education programme was made of five sessions (information, ergonomics, extension exercises). RESULTS: Comparing the two populations we did not observe significant differences concerning the age, the body mass index, the anxiety and depression levels, the pain (VAS, SAPA, RIII nociceptive reflex), the lumbar stiffness, the lumbar disability, the quality of life; the patients who had achieved back school had a peak torque of the flexors and a ratio flexors/extensors significantly lower. Comparing men and women we observed significant differences in the SAPQ and the muscles strength. The SAPQ was correlated with the depression and anxiety levels, the lumbar disability, the peak torque of the flexors. The VAS was correlated with the age, the lumbar stiffness, the depression level, the peak torque of the flexors. The RIII nociceptive reflex was correlated with the ratio flexors/extensors. CONCLUSION: This study present some biases but this objective assessment of chronic low back pain appeared as feasible. The pain must be investigated in term of intensity, expression, alleviation. The impairment of the flexors muscles in women and after back school has to be confirmed. The different tests are relevant to determinate the efficiency of the back school programmes.

Adult↗
PubMed2000

Quantification of fingertip force reduction in the forefinger following simulated paralysis of extensor and intrinsic muscles.

Objective estimates of fingertip force reduction following peripheral nerve injuries would assist clinicians in setting realistic expectations for rehabilitating strength of grasp. We quantified the reduction in fingertip force that can be biomechanically attributed to paralysis of the groups of muscles associated with low radial and ulnar palsies. We mounted 11 fresh cadaveric hands (5 right, 6 left) on a frame, placed their forefingers in a functional posture (neutral abduction, 45 degrees of flexion at the metacarpophalangeal and proximal interphalangeal joints, and 10 degrees at the distal interphalangeal joint) and pinned the distal phalanx to a six-axis dynamometer. We pulled on individual tendons with tensions up to 25% of maximal isometric force of their associated muscle and measured fingertip force and torque output. Based on these measurements, we predicted the optimal combination of tendon tensions that maximized palmar force (analogous to tip pinch force, directed perpendicularly from the midpoint of the distal phalanx, in the plane of finger flexion-extension) for three cases: non-paretic (all muscles of forefinger available), low radial palsy (extrinsic extensor muscles unavailable) and low ulnar palsy (intrinsic muscles unavailable). We then applied these combinations of tension to the cadaveric tendons and measured fingertip output. Measured palmar forces were within 2% and 5 degrees of the predicted magnitude and direction, respectively, suggesting tendon tensions superimpose linearly in spite of the complexity of the extensor mechanism. Maximal palmar forces for ulnar and radial palsies were 43 and 85% of non-paretic magnitude, respectively (p<0.05). Thus, the reduction in tip pinch strength seen clinically in low radial palsy may be partly due to loss of the biomechanical contribution of forefinger extrinsic extensor muscles to palmar force. Fingertip forces in low ulnar palsy were 9 degrees further from the desired palmar direction than the non-paretic or low radial palsy cases (p<0.05).

Cadaver↗
PubMed2002

Bone mineral density in adolescent female athletes: relationship to exercise type and muscle strength.

PURPOSE: This study investigated the influence of different exercise types and differences in anatomical distribution of mechanical loading patterns on bone mineral density (BMD) in elite female cyclists, runners, swimmers, triathletes, and controls (N = 15 per group). Associations between leg strength and BMD were also examined. METHODS: Areal BMD (g x cm(-2)) was assessed by duel-energy x-ray absorptiometry (DXA) (total body (TB), lumbar spine (LS), femoral neck (FN), legs, and arms). Right knee flexion and extension strength was measured using a Cybex Norm isokinetic dynamometer at 60 degrees x s(-1). RESULTS: Runners had significantly higher unadjusted TB, LS, FN, and leg BMD than controls (P < 0.05); higher TB, FN, and leg BMD than swimmers (P < 0.05); and greater leg BMD than cyclists (P < 0.05). Absolute knee extension strength was significantly (P < 0.01) correlated (0.33 < or = r < or = 0.44) with TB, FN, LS, and leg BMD for all groups combined. Weaker but still significant correlations (0.28 < or = r < or = 0.33) existed for normalized (per leg lean tissue mass) knee extension strength and all BMD sites, except FN BMD. There were no significant correlations between absolute or normalized knee flexion strength and any of the BMD variables. Absolute knee extension strength was entered as the second independent predictor for LS and leg BMD in stepwise multiple linear regression analysis (MLRA), accounting for increments of 4% and 12%, respectively, in total explained variation. CONCLUSION: We conclude that running, a weight bearing exercise, is associated with larger site-specific BMD than swimming or cycling, that the generalized anatomical distribution of loads in triathlon appears not to significantly enhance total body BMD status, and that knee extension strength is only a weak correlate and independent predictor of BMD in adolescent females.

Adolescent↗
PubMed1990

Isokinetic study of muscle strength in osteoarthritic knees of females.

The present investigation was aimed at assessing the difference in peak torque between normal and osteoarthritic (OA) knees in females. Fifty-five female osteoarthritic patients with 85 osteoarthritic knees were studied. Thirty-three normal females of similar age were also collected as a control group. The muscle torque of the knee flexor and extensor was assessed by a Cybex II dynamometer. The speed of isokinetic contraction was set at 30 RPM, 5 RPM, and 0 RPM. The muscle torque of the affected knee in patients with unilateral osteoarthritis was found to be significantly greater than that of those with bilateral osteoarthritis (p less than 0.05). The peak torque of OA patients at the faster speed (30 RPM) showed significant deterioration with age. Compared with the value for controls, the deficit of peak torque in geriatric patients was significant (p less than 0.05), especially at the faster speed (30 RPM). The decrease in extensor torque in OA knees tended to be greater than that of flexor torque, especially in patients less than 51 years of age at 5 RPM and 0 RPM. Age, duration of illness and the grading of X-ray change accounted for isokinetic torque differences in osteoarthritic knees.

Adult↗
PubMed2001

Muscle power of the ankle flexors predicts functional performance in community-dwelling older women.

OBJECTIVES: To test the hypothesis that peak power of the ankle flexors is related to physical functioning in older women with functional limitations. DESIGN: A cross-sectional study. SETTING: University-based human physiology laboratory. PARTICIPANTS: Thirty-four older women (75.4 +/- 5.1 years, 67.8 +/- 11.3 kg, body mass index 27.4 +/- 4.5) with self-reported functional limitations. MEASUREMENTS: Plantarflexion (PF) and dorsiflexion (DF) peak power and isometric strength with physical performance (stair climb time, repeated chair rise time, maximal and habitual gait velocity) were determined. An isokinetic dynamometer was used to measure isometric strength, isokinetic peak torque and power of PF and DF at five angular velocities (30 degrees, 60 degrees, 90 degrees, 120 degrees, and 180 degrees.sec-1), and isometric strength. RESULTS: Peak torque for both PF and DF declined with increasing velocity of movement (PF: P <.0001; DF: P <.0001), whereas peak power increased with increasing velocity up to 120 degrees.sec-1. The strongest univariate associations were found between chair rise time and DF peak power (r = 0.50; P <.002), stair climb time and DF peak power (r = 0.49; P <.003), habitual gait velocity and PF isometric strength (r = 0.53; P <.001), and maximal gait and PF isometric strength (r = 0.47; P <.005). Multivariate regression analysis revealed that DF and PF peak power along with the physical functioning and general health scores from the Medical Outcomes Study Short Form were independent predictors of chair and stair climb performance. CONCLUSION: These data suggest that ankle muscle power together with self-reported measures of health and physical functioning are essential components of functional mobility in older women with functional limitations.

Activities of Daily Living↗
PubMed1988

A quantitative analysis of donor site morbidity after vascularized fibula transfer.

Eleven patients with free vascularized fibula graft transplants to the upper extremity were studied for donor-side morbidity effects. Based on their surgical follow-up times, the patients were divided into either group 1 (5 +/- 2 months) or group 2 (21 +/- 8 months) to examine the effects of surgical trauma more closely. Gait evaluation was performed using two walkways containing different ground conditions. Knee and ankle-foot motion was measured using a three-dimensional electrogoniometer. Basic temporodistance factors and ground reactions were obtained from foot switches, instrumented floor mats, and a force plate. A modified Cybex II isokinetic dynamometer was used to quantitate ankle-foot strengths. Moderate knee and ankle-foot motion changes were seen while walking on the level, sideslope, and ramp in patients evaluated less than 10 months after their surgical procedure. Minimal joint motion effects were discovered in patients with follow-up times longer than 10 months. Muscle strengths were significantly impaired in both groups, especially foot inversion and eversion. An inverse relationship existed between the length of resected fibula and ankle evertor muscle strength. Donor side morbidity does not appear to be caused by surgical soft-tissue trauma exclusively. These patients need to be studied for several more years to determine the long-term functional effects of free vascularized fibular graft transfer.

Adult↗
PubMed2001

Changes in isokinetic torque and muscular activity of elbow flexors muscles with age.

This study examined the influence of aging on torque-angular velocity relationships for elbow flexion and the corresponding muscular activity levels in order to target the mechanisms involved in the eccentric muscle action in older adults. Maximal constant angular torque (CAT) at 90 degrees was measured at different angular velocities for concentric (CON; 60, 120, 180, 240 degrees s(-1)), isometric (ISO) and eccentric (ECC; -60, -120 degrees s(-1)) elbow flexor muscle actions in older (OG; 6 females and 4 males, 64-82 years) and young adult subjects (YG; 6 females, 6 males, 19-24 years) on an isokinetic dynamometer. Myoelectrical activity was quantified on biceps and triceps muscles, using the root mean square (RMS) procedure over a range of 30 degrees motion (75-105 degrees ). Absolute CAT was significantly greater (p<0.04) for YG in comparison with OG for all types of actions (CON, ECC, ISO). The only effect of gender concerned absolute strength values (p=0.00007). However, the OG showed higher (p<0.001) relative CAT values (expressed as percentage of CON 60 degrees s(-1) value) during ECC muscle action than the YG. Nevertheless, RMS values for elbow flexors were significantly (p<0.03) lower in the OG than in the YG. The antagonist (triceps) co-activation was similar for both groups. The relative ECC force preservation with aging seems to be independent of a muscular activation phenomenon.

Adult↗
PubMed2002

The association between nutritional status and handgrip strength in older Rwandan refugees.

OBJECTIVES: To investigate the association between nutritional status and handgrip strength in older Rwandan refugees. DESIGN: Cross-sectional study. SETTING: Rwandan refugee camp located in Karagwe district in the north-west of Tanzania. The study was carried out in the post-emergency phase. The response rate was 85%. SUBJECTS: A total of 413 men and 415 women aged 50-92 y participated in the study. METHODS: Weight, height, mid-upper-arm circumference (MUAC) and triceps skinfold were obtained using standard techniques. For people with visible kyphosis, height was estimated from armspan using regression equations developed from non-kyphotic subjects within the sample. Handgrip was measured using a mechanical handgrip dynamometer. Information regarding physical activity and health status was obtained by interview and clinical screening. RESULTS: Handgrip strength (kg) was significantly higher in men than in women (30.3+/-6.7 vs 22.3+/-5.1), and significantly lower in each older age group in both sexes. Handgrip strength was positively correlated to BMI (body mass index) and AMA (arm muscle area). The relative risk of impaired handgrip strength in individuals with poor nutritional status (BMI<18.5 kg/m(2)) compared with those of adequate nutritional status was 1.75. After controlling for potential confounders (sex, age and height), BMI remained a significant contributor to the variation in handgrip strength. CONCLUSION: Poor nutritional status is associated with poor handgrip strength independent of sex, age and height, in this refugee population. This may indicate that underweight older people are likely to have more difficulties in functioning independently in the community. Research is needed to investigate if improving nutritional status can lead to better functional ability. SPONSORSHIP: Department for International Development (UK) and HelpAge International.

Aged↗
PubMed1999

Demonstration of delayed recovery from fatiguing exercise in chronic fatigue syndrome.

Patients with the chronic fatigue syndrome (CFS) complain consistently of delay in recovery of peripheral muscle function after exercise. The purpose of this study was to try to confirm this observation. A fatiguing exercise test was carried out on the quadriceps muscle group of ten patients and ten control subjects. The test consisted of 18 maximum voluntary contractions (MVCs) with a 50% duty cycle (10 s contraction, 10 s rest), and the force generated by each contraction was recorded using a KinCom dynamometer. This was followed by a recovery phase lasting 200 min in which quadriceps strength was evaluated at increasing intervals, and a follow-up session at 24 h post-exercise involving three 10 s MVCs. Throughout the exercise period, the MVCs obtained from the control group were significantly higher than those of the patient group (P = 0.006), but both groups showed a parallel decline in force over the 18 contractions, in keeping with a similar endurance capacity. Recovery was prolonged in the patient group, however, with a significant difference compared to initial MVCs being evident during the recovery phase after exercise (P = 0.001) and also at 24 h (P < 0.001). In contrast, the control group achieved MVCs which were not significantly different from initial values during the recovery phase, and maintained these at 24 h. These findings support the clinical complaint of delayed recovery after exercise in patients with CFS.

Adult↗
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↗