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PubMed2003

Effect of menstrual cycle phase on the concentration of bioavailable 17-beta oestradiol and testosterone and muscle strength.

To investigate the effect of changes in sex hormone concentration on muscle strength and the bioavailability of 17-beta oestradiol (oestradiol) and testosterone, seven eumenorrheic females were tested during two phases of the menstrual cycle. Maximum voluntary isometric strength of the first dorsal interosseus muscle was measured during the early follicular and mid-luteal phases of the menstrual cycle. These phases were chosen for testing as the concentration of total oestradiol is significantly different in these two phases. Total oestradiol has been repeatedly associated with changes in muscle strength in females, whereas the effects of bioavailable oestradiol are unknown. The concentrations of total and bioavailable oestradiol and testosterone were measured in addition to the concentration of total progesterone. Concentrations of total progesterone and oestradiol were significantly different between the early follicular and mid-luteal phases of the menstrual cycle (P <0.05 and P <0.001 respectively). The concentration of total testosterone (0.7+/-0.2 and 0.8+/-0.1 nmol.l(-1) respectively) and the ratio of total oestradiol to progesterone (153.0+/-251.2 and 108.5+/-27.8 respectively) did not change significantly between the early follicular and mid-luteal phases. Bioavailable testosterone (102.2+/-66.3 and 105.0+/-90.2 pmol.l(-1) respectively) and bioavailable oestradiol (90.5+/-35.5 and 120.0+/-60.6 pmol.l(-1) respectively) did not differ significantly between phases. There were no significant differences in muscle strength during the menstrual cycle (P =0.1). Mean maximum voluntary isometric force of the first dorsal interosseus muscle did not correlate significantly with the mean concentration of any reproductive hormone measured. These results indicate that cyclical variation in endogenous reproductive hormones does not affect muscle strength.

Adult↗

PubMed2002

Assessment of isokinetic muscle strength in women who are obese.

STUDY DESIGN: Cross-sectional study of isokinetic trunk and knee muscle strength in women who are obese. OBJECTIVE: To provide reference values, to identify variables that affect peripheral muscle strength, and to provide recommendations for isokinetic testing of trunk and knee muscles in women who are obese and morbidly obese. BACKGROUND: The assessment of peripheral muscle strength is useful for the quantification of possible loss of strength, for exercise prescription, and for the evaluation of the effect of training programs in obese individuals. METHODS AND MEASURES: Isokinetic trunk and leg muscle strength was assessed in 241 women who were obese (18-65 years, body mass index (BMI) > or = 30 kg/m2). Trunk flexion and extension peak torque (PT) was measured using the Cybex TEF dynamometer; trunk rotation (TR) PT was measured using the Cybex TORSO dynamometer; and knee flexion/extension (KFE) PT was measured using the Cybex 350 dynamometer. Body composition was assessed using the bioelectrical impedance method; physical activity was assessed using the Baecke questionnaire; and peak VO2 was assessed using an incremental exercise capacity test on a bicycle ergometer. To identify variables related to muscle strength, Pearson correlations were computed and a stepwise multiple regression analysis was performed. RESULTS: Pearson correlation coefficients of all strength measurements at 60 degrees/s revealed low-to-moderate negative associations with age and positive associations with mass, height, fat free mass (FFM), and peak VO2 (P < 0.05), except for gravity-uncorrected trunk extension strength, which was not related to mass. The sports index of the Baecke questionnaire was associated with TR PT (r = 0.20, P < 0.01) and KFE PT (r = 0.18, P < 0.05). CONCLUSION: The weight of the trunk accounts largely for the measured trunk extensor and flexor strength in women who are obese. Contributing variables of isokinetic trunk flexion and extension strength in women who are obese are age, height, and FFM; whereas sports activities and aerobic fitness are contributing factors for trunk rotational and knee extension strength. Recommendations for measuring isokinetic muscle strength in individuals who are obese are provided.

Adult↗

PubMed2004

Creatine monohydrate supplementation does not increase muscle strength, lean body mass, or muscle phosphocreatine in patients with myotonic dystrophy type 1.

Creatine monohydrate (CrM) supplementation may increase strength in some types of muscular dystrophy. A recent study in myotonic muscular dystrophy type 1 (DM1) did not find a significant treatment effect, but measurements of muscle phosphocreatine (PCr) were not performed. We completed a randomized, double-blind, cross-over trial using 34 genetically confirmed adult DM1 patients without significant cognitive impairment. Participants received CrM (5 g, approximately 0.074 g/kg daily) and a placebo for each 4-month phase with a 6-week wash-out. Spirometry, manual muscle testing, quantitative isometric strength testing of handgrip, foot dorsiflexion, and knee extension, handgrip and foot dorsiflexion endurance, functional tasks, activity of daily living scales, body composition (total, bone, and fat-free mass), serum creatine kinase activity, serum creatinine concentration and clearance, and liver function tests were completed before and after each intervention, and muscle PCr/beta-adenosine triphosphate (ATP) ratios of the forearm flexor muscles were completed at the end of each phase. CrM supplementation did not increase any of the outcome measurements except for plasma creatinine concentration (but not creatinine clearance). Thus, CrM supplementation at 5 g daily does not have any effects on muscle strength, body composition, or activities of daily living in patients with DM1, perhaps because of a failure of the supplementation to increase muscle PCr/beta-ATP content.

Activities of Daily Living↗

PubMed1994

Muscle strength, voluntary activation, twitch properties, and endurance in patients with fibromyalgia.

Previous studies have shown decreased voluntary muscle strength and endurance in patients with fibromyalgia. The aim of this study was to determine to what extent this is due to lack of exertion. The twitch interpolation technique was used to determine the degree of central activation and estimate the "true" quadriceps muscle strength in patients with fibromyalgia and age and sex matched controls. Subjects hereafter performed an endurance test consisting of repetitive contractions at 50% of estimated "true" muscle strength of four seconds duration followed by a six second rest until exhaustion, or maximally for 40 minutes. Twitch decline and increases in mean rectified EMG were used as objective markers of fatigue. The estimated "true" muscle strength was 82 (SD 26) Nm in 20 patients with fibromyalgia compared with 133 Nm (SD 28) Nm in the 21 controls (p < 0.001). The "true" muscle strength per cm2 midthigh cross sectional area was lower 0.50 (SD 0.15) Nm/cm2 in the patients compared with 0.74 (SD 0.15) Nm/cm2 in the controls (p < 0.001). The decline over time in twitch sizes was similar in the two groups. The mean rectified EMG signal at a fixed force level of 50% of "true" muscle strength increased similarly in the two groups. Relaxation rates and contraction rates also increased equally in the two groups. In conclusion, a reduction of the estimated muscle strength per area unit of about 35% was found in the patients with fibromyalgia. This might be secondary to physical inactivity or neuroendocrine factors. No differences in changes in the neurophysiological indices associated with fatigue were found between the two groups.

Adult↗

PubMed1991

1,25-Dihydroxyvitamin D3 and muscle strength in the elderly: a randomized controlled trial.

An unexplained loss of muscle strength occurs with aging. Vitamin D deficiency can cause myopathy and administration of 1,25-dihydroxyvitamin D3 [1,25-(OH2)D3] to persons with low serum concentrations can improve strength. To test the hypothesis that the weakness associated with aging is in part due to inadequate serum concentrations of [1,25-(OH2)D3], we conducted a randomized, controlled, double blinded trial in 98 men and women volunteers over 69 yr old. Treatment consisted of 0.25 micrograms 1,25-(OH)2D3, orally, twice per day or identical placebo for 6 months. Leg muscle strength of the quadriceps was measured with an isokinetic dynamometer. There was no difference between the two groups at 1 week, 1 month, or 6 months of treatment in any of the measures of muscle strength. We conclude that oral administration of 0.5 micrograms 1,25-(OH)2D3/day does not improve muscle strength in older persons. Further research is needed to determine the etiology of the decline in muscle strength associated with aging.

Aged↗

PubMed2006

Joint laxity and the relationship between muscle strength and functional ability in patients with osteoarthritis of the knee.

OBJECTIVE: To establish the impact of knee joint laxity on the relationship between muscle strength and functional ability in osteoarthritis (OA) of the knee. METHODS: A cross-sectional study of 86 patients with OA of the knee was conducted. Tests were performed to determine varus-valgus laxity, muscle strength, and functional ability. Laxity was assessed using a device that measures the angular deviation of the knee in the frontal plane. Muscle strength was measured using a computer-driven isokinetic dynamometer. Functional ability was assessed by observation (100-meter walking test) and self report (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]). Regression analyses were performed to assess the impact of joint laxity on the relationship between muscle strength and functional ability. RESULTS: In regression analyses, the interaction between muscle strength and joint laxity contributed to the variance in both walking time (P = 0.002) and WOMAC score (P = 0.080). The slope of the regression lines indicated that the relationship between muscle strength and functional ability (walking time, WOMAC) was stronger in patients with high knee joint laxity. CONCLUSION: Patients with knee OA and high knee joint laxity show a stronger relationship between muscle strength and functional ability than patients with OA and low knee joint laxity. Patients with OA, high knee joint laxity, and low muscle strength are most at risk of being disabled.

Aged↗

PubMed2005

Decreased isometric muscle strength after acute hyperglycaemia in Type 1 diabetic patients.

AIMS: Fatigue is a common complaint in diabetic patients during periods of hyperglycaemia. To test whether muscle performance is reduced during acute hyperglycaemia, diabetic patients were studied whilst performing maximal isokinetic and isometric contractions. METHODS: In this double-blind placebo controlled study, maximal isometric and isokinetic muscle strength was determined in seven Type 1 diabetic patients during normo- and hyperglycaemia using a hyperglycaemic clamp technique. On two separate days, maximal muscle strength of the knee extensors was determined quantitatively using a dynamometer. On both days, muscle strength was determined before a constant blood glucose level was obtained and after the blood glucose level had been kept constant at either 5 or 16 mmol/l for 3 h. Percentage of change from baseline at the two glycaemic levels were calculated and compared. In addition, the changes from baseline at these glycaemic levels were related to glucose turnover. RESULTS: Following hyperglycaemia, a significant decrease in maximal isometric muscle strength was found as compared with normoglycaemia (86 vs. 104% of the initial level) (P = 0.018). In contrast, no alteration of maximal isokinetic muscle strength was found comparing normo- and hyperglycaemia (96 and 95%) (P = 0.74). Changes in muscle strength were not significantly related to either basal or hyperglycaemic glucose turnover. CONCLUSIONS: A few hours of hyperglycaemia in Type 1 diabetic patients leads to a reduction of isometric muscle performance, whereas isokinetic muscle strength is unchanged. The reduction in muscle strength could play a role in the development of fatigue and is related more closely to ambient glucose concentrations than to systemic glucose availability.

Adult↗

PubMed1979

Influence of muscle temperature on maximal muscle strength and power output in human skeletal muscles.

The influence of muscle temperature (Tm) on maximal muscle strength, power output, jumping, and sprinting performance was evaluated in four male subjects. In one of the subjects the electromyogram (EMG) was recorded from M. vastus lateralis, M. biceps femoris, and M. semitendinosus. Tm ranged from 30.0 degrees C to 39 degrees C. Maximal dynamic strength, power output, jumping, and sprinting performance were positively related to Tm. The changes were in the same order of magnitude for all these parameters (4-6% x degrees C-1) Maximal isometric strength decreased by 2% x degrees C-1 with decreasing Tm. The force-velocity relationship was shifted to the left at subnormal Tm. Thus in short term exercises, such as jumping and sprinting, performance is reduced at low Tm and enhanced at Tm above normal, primarily as a result of a variation in maximal dynamic strength.

Adult↗

PubMed2003

Acceleration effects on neck muscle strength: pilots vs. non-pilots.

BACKGROUND: Conditioning of neck muscles, if any, due to repeated exposures to +Gz forces has received little research attention. OBJECTIVE: This study was conducted to evaluate and compare the neck muscle strength of test volunteers representative of the general populations of fighter aircraft pilots and non-pilots. METHODS: The tests were performed using a special attachment device on a computerized dynamometer. Ten pilots and ten non-pilots volunteered as test subjects. Each individual's maximal isometric neck muscle strength was evaluated in the extension, flexion, and left and right lateral bending directions in a single day. Peak values from the measurements were used for data analysis. Overall neck strength was calculated as the mean values for the four directions in each group. RESULTS: The overall muscular strength of the necks of pilots did not differ significantly from that of non-pilots, nor did exposure to +Gz forces lead to specific changes in isometric muscle strength across any of the four principal directions. Neck muscle strength in the four measured directions pooled across the two subgroups were statistically significant. The widespread practice of adopting protective head-positioning strategies to minimize neck strains, coupled with results from this research study, suggest that the neck muscles are subjected to reduced in-flight strengthening workouts during exposures to +Gz forces. CONCLUSIONS: To maximize in-flight performance and minimize +Gz-induced neck injuries, fighter pilots should be encouraged to perform on-land neck muscle strengthening exercise and in-flight head-positioning techniques. More research is needed to fine-tune this countermeasure strategy against cervical spine injury.

Adult↗

PubMed1982

Trunk muscle strength and low back pain.

The strength of the trunk muscles was measured in a group of young males with low back insufficiency (n=7) and in an age matched (19-21 yrs) healthy control group (n=8). A recently designed new application of the isokinetic technique was used to record maximal torque produced by the trunk muscles during flexion, extension and lateral flexion. Trunk muscle strength was measured during isometric contractions in different trunk positions and during slow isokinetic contractions in the whole range of motion. No significant differences between the groups were observed for trunk extension, lateral flexion or flexion with the centre of rotation at L2-L3 level. However, in the initial part of isokinetic trunk flexion with the pivot point at the hip joint the strength values for the back patients were significantly lower than for the controls. The present results demonstrate the importance of a comprehensive approach to the assessment of trunk muscle strength, including different movement velocities, body positions and pivot points. Further studies are needed to evaluate the significance of the specific weakness observed in dynamic trunk flexion strength in the back patients.

Adult↗

PubMed2003

Antiandrogens in hormonal contraception limit muscle strength gain in strength training: comparison study.

AIM: To determine antiandrogen effects on muscle strength gain and fat-free mass increase during exercise in women using hormonal contraception with antiandrogen content. METHODS: The study included 50 women (age range, 18-30 years; mean-/+SD, 26-/+3) using hormonal contraception for at least 12 months before the beginning of the study. They were divided into two groups: "antiandrogen" group (n=26) and "estrogen-progestogen" group (n=24) groups. The subjects participated in strength training sessions 3 times a week during 16 weeks. Initially, there were no differences between the groups in fat-free mass, muscle strength, or maximum oxygen uptake. The parameters were measured before, during, and after the training period. RESULTS: After the training period, the mean increase of fat-free mass was significantly greater in the estrogen-progestogen group (p<0.001). The mean gain in the muscle strength (in Newtons) was also more evident in estrogen-progestogen group (1289.0-/+17.1 N vs 101.9-/+18.5 N; p<0.001). There were no differences in the maximum oxygen consumption (VO(2)max). CONCLUSION: Antiandrogens had a negative effect on muscle strength, minimizing the effects of strength training in women. Hormonal contraception containing antiandrogens should be avoided in young exercising women.

Adolescent↗

PubMed1990

Influence of simultaneous bilateral exertion on muscle strength during voluntary submaximal isometric contraction.

The influence of simultaneous bilateral exertion on muscle strength was tested under the conditions in which the same or different levels of strength were exerted by the right and left arm (or hand). Isometric muscle strength of elbow flexion, elbow extension and hand grip was studied. Subjects voluntarily exerted 25%, 50%, and 75% of maximal strength based on their subjective judgement without the feedback of the strength actually exerted. Involuntary decrements of muscle strength were caused by the bilateral exertion. Muscle strength of both sides decreased under the condition where the same level of strength was exerted by the right and the left arm (or hand). When different levels of strength were exerted by each arm (or hand), the strength of the weaker side considerably decreased, while the strength of the stronger side did not decrease.

Adolescent↗

PubMedDate not supplied

Recovery from disuse osteopenia coincident to restoration of muscle strength in mdx mice.

The objective of this study was to compare the tibial structure and the strength of the tibia during muscle weakness and after recovery in mdx mice (which demonstrate X-linked muscular dystrophy and subsequent muscle regeneration) and age-matched control mice. The extent of disuse atrophy produced by muscle weakness and recovery following restoration of normal muscle strength could then be determined. The tibiae adjacent to weakened tibialis anterior muscles of 4-week-old mdx mice had significantly reduced radiographic density (p < 0.05) and cortical thickness (p < 0.001), and increased porosity (p < 0.001) compared to age-matched controls, suggesting development of disuse osteopenia. Significantly less force was required to break mdx tibiae than age-matched control tibiae (p < 0.05). In addition, Sharpey's fiber density was reduced (p < 0.001), suggesting a weakened attachment of the tibialis anterior muscle to bone. At 12 weeks, during the period of muscle regeneration, mdx tibial cortical thickness (p < 0.001) and porosity (p < 0.01) remained significantly lower, but percent calcium and Sharpey's fiber and radiographic densities were significantly greater (p < 0.001) than in age-matched controls, suggesting that bone mineralization and muscle attachment strength had increased to above normal levels in parallel with recovery of strength by the attached muscle. By 18 weeks, mdx tibial cross-sectional area, cortical thickness, and porosity remained significantly less (p < 0.001) than normal. Although Sharpey's fiber density was greater than in age-matched controls (p < 0.001) by 18 weeks, mdx tibial percent calcium (p < 0.005) and Sharpey's fiber density (p < 0.001) were significantly reduced from levels in 12-week-old mdx animals. There was significantly less deformation of the tibia prior to fracture in mdx than control tibiae at 18 weeks of age, suggesting tibial brittleness. Thus, at the site of attachment of mdx muscle to osteopenic bone, the remodelling which accompanies recovery of muscle strength is atypical, and produces an attachment of greater strength than function appears to require. These observations suggest that data are needed regarding bone mass and muscle-bone attachments in humans with disuse osteopenia, DMD, and other neuromuscular diseases.

Animals↗

PubMed2005

Circulating angiotensin converting enzyme activity is correlated with muscle strength.

PURPOSE: The D-variant of the angiotensin-1 converting enzyme (ACE) gene is associated with higher circulating and tissue ACE activity. Some studies have suggested a similar association of genotype with muscle strength or the gain in strength in response to training. This study has assessed the relationship between circulating ACE activity, strength, and the response to training. METHODS: Eighty-one untrained men were tested for quadriceps muscle strength, and 44 of these performed an 8-wk program of dynamic strength training of the quadriceps muscle group. Venous blood was obtained for assessment of circulating ACE activity before and after the training program. ACE genotype was also determined. RESULTS: At baseline, circulating ACE activity was significantly correlated with isometric (r = 0.25-0.29, P < 0.02) and isokinetic (r = 0.38, P < 0.0005) quadriceps muscle strength. ACE genotype also seemed to be related to pretraining muscle strength. However, circulating ACE activity showed no significant association with the 9-14% mean increases of muscle strength in response to the training intervention. ACE genotype also showed no association with the training-induced change in muscle strength. Circulating ACE activity did not change significantly after the training program. CONCLUSIONS: The data support a role for ACE in the regulation of human skeletal muscle strength, but do not confirm a role in altering the response to short-term training.

Adolescent↗

PubMed1982

A statistical analysis of the loss of muscle strength in Duchenne's muscular dystrophy.

We have confirmed that the loss of muscle strength in 12 boys with Duchenne's muscular dystrophy, as measured by manual muscle testing, approximates a linear decay model, but we have also found that it fits as well a first order decay model. The strength in the same eight muscles was measured over time. Results of an analysis of 111 examinations are reported here. An arbitrary numerical scale for grading muscle strength was used, such that normal was 13 units, and no movement was zero. The maximal sum, if all 8 muscles were normal, would be 104 units. Pooling all measurements, the linear decay rate in this sum was -0.189 +/- 0.023 (estimate +/- standard error) arbitrary muscle strength units . month-1. The corresponding first order fractional decay rate was -0.0034 +/- 0.0004 month-1. However, a more detailed statistical analysis indicated that decay rates in muscle strength were not homogeneous, i.e. muscle strength decayed faster in some patients than others. The decay constants in 11 of the 12 subjects spanned a 10-fold range, and in one subject increased the spread to 40-fold. The distribution frequency of decay rates appears to be bimodal. In these assessments, the muscle strength at time zero was not known. Therefore, an estimate of muscle strength at 10 years was made. This varied from 34 to 71 units. The group mean was 53.0 units using the exponential model, i.e. on average, only 51% (= 53.0/104 X 100) of the normal muscle strength remained in the 8 muscle groups assessed at age 10 years. In conclusion, a quantitative characterization of muscle strength deterioration is reported, which emphasizes the heterogeneity in this disease. This approach may eventually allow quantitative distinctions between Duchenne's and Becker's varieties of muscular dystrophy.

Adolescent↗

PubMedDate not supplied

Influence of time of day and partial sleep loss on muscle strength in eumenorrheic females.

Disrupted sleep is the most common form of sleep deprivation in travellers, shift workers, athletes the night before important competitions and among parents of infants. The influence of partial sleep loss on muscle strength might differ according to the time of testing on the following day. This study was therefore designed to assess the interaction between the effects of partial sleep loss and time of day on muscle strength in females. Eight sedentary eumenorrheic females (mean +/- SD; age 30 +/- 6 years, height 1.62 +/- 0.06 m and body mass 67 +/- 5.0 kg) took part in the study, in a counterbalanced design. Measurements of muscle strength were carried out at 06:00 and 18:00 hours after the one control night (no sleep loss) and the one night of partial sleep loss, during menses. Muscle strength measures included isokinetic (at 1.05, 3.14 rad s(-1); 90 degrees range of motion) and isometric peak torque (at 60 degrees of knee flexion) of knee extensors and flexors (dominant leg). In addition, isometric force of knee extensors with super-imposed electrical twitches (50 Hz, 250 V, 200 mus pulse width) was measured using the same procedure in order to control for motivation. Rectal temperature was measured during the 30 min before muscle strength measurements. Partial sleep loss consisted of allowing 2.5 h sleep (between 03:00 and 05:30 h), whilst in the control condition (no sleep loss) subjects retired between 22:30 and 23:30 h, rising at 05:30 hours. All measurements were conducted at just one phase of the menstrual cycle (menses) to prevent any masking effect due to different phases of the menstrual cycle. In both conditions (with and without partial sleep loss) a diurnal variation was observed in peak torque of knee flexors at 1.05 (F(1,7) = 5.5, p < 0.05) and 3.14 rad s(-1) (F(1,7) = 8.0, p < 0.05); values at 18:00 hours were 4.5 and 5.9% higher than at 06:00 hours, respectively. No significant diurnal variation was observed for the other muscle strength measures. No significant effect of partial sleep loss or interaction effect (sleep x time of day) was observed for muscle strength measures. However, the performance rhythms were in phase with the circadian rhythm in rectal temperature. Partial sleep deprivation over one night did not have any adverse effect on maximal muscle strength, nor on diurnal variations of muscle strength indices. As the effect of time of day was observed with some of the muscle strength measures, it is suggested that, in designing future studies using females, the control of time of day is essential.

Adult↗

PubMed2002

Lower extremity muscle strength does not independently predict proximal femur bone mineral density in healthy older adults.

The relationship described in the published literature between muscle strength and bone mineral density of older adults is not entirely certain. It is possible that the direct relationship reported in some studies is biased by failing to mathematically account for the biological influence of body weight and body height on both bone mineral density and muscle strength. This study sought to determine if the relationships between measures of lower extremity muscle strength and bone mineral density of the proximal femur are independent of body size (i.e., body height and body weight) in healthy older adults. We recruited 50 older women and 29 older men, all of whom were healthy community dwellers and not involved in resistance training. Quantitative analysis of the isometric strength of the bilateral ankle, knee, and hip joints and assessment of bone mineral density of the proximal femur were conducted. Muscle strength values were adjusted for the influence of body height and body weight using an allometric scaling procedure. The correlations between proximal femur bone mineral density and the unadjusted strength values were weak but statistically significant. After adjusting muscle strength to account for the influence of body height and body weight, the magnitudes of the correlations between bone mineral density and muscle strength diminished substantially and were not significantly different from zero. The results reveal that, for a typical sample of healthy older adults not involved in resistance training, the relationship between maximal isometric muscle strength of lower extremity joints and proximal femur bone mineral density is reliant on body size.

Aged↗

PubMed2004

Effect of three anaesthetic techniques on isometric skeletal muscle strength.

BACKGROUND: Our aim was to quantify human involuntary isometric skeletal muscle strength during anaesthesia with propofol, sevoflurane, or spinal anaesthesia using bupivacaine. METHODS: Thirty-three healthy patients undergoing anaesthesia for elective lower limb surgery were investigated. Twenty-two patients received a general anaesthetic with either propofol (n=12) or sevoflurane (n=10); for the remaining 11 patients spinal anaesthesia with bupivacaine was used. We used a non-invasive muscle force assessment system before and during anaesthesia to determine the contractile properties of the ankle dorsiflexor muscles after peroneal nerve stimulation (single, double, triple, and quadruple stimulation). We measured peak torques; contraction times; peak rates of torque development and decay; times to peak torque development and decay; half-relaxation times; torque latencies. RESULTS: Males elicited greater peak torques than females, medians 6.3 vs 4.4 Nm, respectively (P=0.0002, Mann-Whitney rank-sum test). During sevoflurane and propofol anaesthesia, muscle strength did not differ from pre-anaesthetic values. During spinal anaesthesia, torques were diminished for single-pulse stimulation from 3.5 to 2.0 Nm (P=0.002, Wilcoxon signed rank test), and for double-pulse from 7.6 to 5.6 Nm (P=0.02). Peak rates of torque development decreased for single-pulse stimulation from 113 to 53 Nm s(-1) and for double pulse from 195 to 105 Nm s(-1). Torque latencies were increased during spinal anaesthesia. CONCLUSIONS: At clinically relevant concentrations, propofol and sevoflurane did not influence involuntary isometric skeletal muscle strength in adults, whereas spinal anaesthesia reduced strength by about 20%. Muscle strength assessment using a device such as described here provided reliable results and should be considered for use in other scientific investigations to identify potential effects of anaesthetic agents.

Adolescent↗