Improve Muscle Endurance Research Articles

4 weeks of High Intensity Interval Training Improves Muscle Endurance

Muscle endurance is required for completion of normal daily activities and for exercise performance in athletes. It has been shown that the high intensity interval training (HIIT) is a time-efficient method for improving aerobic fitness, but it is not clear to elicit improvements in muscle endurance. PURPOSE: to examine the effects of high-intensity interval training (HIIT) on muscle endurance. METHODS: 8 healthy, young, non-trained, subjects (age: 22 ± 2 years old, body weight: 70.6 ± 11.4 kg, height: 172 ± 7 cm; body fat: 23.3 ± 5.0% ml•kg-1•min-1) completed 4 weeks of HIIT (3 sessions per week, totaling 12 sessions). Each HIIT session consisted of 8-12 cycling exercise stimuli with intensity between 90-110% of the peak power for 60 seconds followed by active recovery intervals of 75 seconds at 30W. Muscle strength was evaluated before and after the HIIT and consisted of 60 maximal knee extension and flexion (total of 60°) of the dominant leg on an dynamometer at maximum speed of 180°•sec-1. Peak and average torque (newton per meter), total (Joules) and relative work (Joules•rep-1), and work fatigue (percent) were recorded for knee extension pre and post HIIT. Data are expressed as mean ± SD and comparisons were using a paired Student t Test. Statistical significance adopted as p≤0.05. RESULTS: HIIT significantly increased VO2max (48.7 ± 5.6 to 51.2 ± 4.8 ml•kg-1•min-1, p<0.05). Peak torque (154 ± 30 to 151 ± 26 N•m-1, p=0.19), average peak torque (93 ± 16 to 97 ± 14 N•m-1, p=0.08) and total work (4004 ± 817 to 3781 ± 3781 Joules, p=0.08) did not increase with HIIT. Relative work per repetition (from 60 ± 11 to 55 ± 11 N•m-1, p=0.02) and work fatigue (70 ± 6 to 67 ± 7 %, p=0.03) reduced with HIIT. Although HIIT did not increase total work and peak torque, it does changed the work per repetition and tended to increase the peak torque per repetition indicating an improved mechanical efficiency and/or better muscle recruitment. CONCLUSION: Our results suggest that 4 weeks of HIIT improves muscle endurance. Supported by FAPEMIG (APQ-01382-12), CAPES and CNPq (407252/2013-4)

Conjugated linoleic acid (CLA) stimulates mitochondrial biogenesis by PGC-1alpha in trained mice

Conjugated linoleic acid (CLA) has been reported to improve muscle hypertrophy, steroidogenesis, physical activity and endurance capacity in mice (1,2), however the mode of action is not completely understood. The aims of the present study were to identify the pathway stimulated by CLA supplementation on mitochondrial biogenesis, one of the most important adaptive response in skeletal muscle after endurance exercise. Mice were randomly assigned to one of four groups (n = 8 per group): placebo sedentary (PLA-SED); CLA sedentary (CLA-SED); placebo trained (PLA-TR); or CLA trained (CLA-TR). The CLA groups were gavaged with 35 μL per day (corresponding to the 0.5% of food ingested, approximately 4 g) Tonalin® FFA 80 food supplement containing CLA throughout the 6 week experimental period, while the placebo groups were gavaged with 35 μL per day sunflower oil. Trained groups performed progressive running on the rotarod for 6 weeks at increasing speed and duration (3). Preliminary findings may suggest that CLA supplementation potentiate mitochondrial biogenesis in trained skeletal muscle via PGC-1 alpha, although further studies need to be conducted to delineate the signaling cascade.

Neutral Spine Control Exercises in Rehabilitation After Lumbar Spine Fusion

Lumbar spine fusion (LSF) has been reported to change the biomechanics of the spine and therefore the rehabilitation after LSF is important. In this study, the effect of selected neutral spine control exercises on activation of trunk muscles after LSF was evaluated. Muscle activity was measured by surface electromyography of the rectus abdominis, external oblique, longissimus, and multifidus muscles during 6 exercises in 22 LSF patients (mean age = 59 years; age range = 25-84 years; 50% women). Muscle activity concurrent with trunk flexion and extension during maximal voluntary isometric contraction (MVIC) was used as a reference value. Pain during the effort was assessed with a visual analog scale (VAS). The highest activity in the rectus abdominis muscles was measured during bilateral shoulder extension (51% of MVIC), and in the external oblique, it occurred during unilateral shoulder horizontal adduction (48% of MVIC) and unilateral hip extension (46% of MVIC) exercises. The highest activation of the multifidus and longissimus muscles (60-104%) was measured during bilateral shoulder flexion and modified Roman chair exercises. The mean (SD) self-reported back pain VAS scores during exercises varied from 3 (7) to 16 (26). Neutral spine control exercises activate trunk muscles and cause minimal pain and are therefore feasible exercises for home-based training to improve muscle endurance and postural control after LSF. In addition, the level of muscle activity during bilateral shoulder flexion and modified Roman chair exercises was over 60% of MVIC, justifying their use in training for strength of the trunk extensor muscles.

Elevated PGC-1α Activity Sustains Mitochondrial Biogenesis and Muscle Function without Extending Survival in a Mouse Model of Inherited ALS

The transcriptional coactivator PGC-1α induces multiple effects on muscle, including increased mitochondrial mass and activity. Amyotrophic lateral sclerosis (ALS) is a progressive, fatal, adult-onset neurodegenerative disorder characterized by selective loss of motor neurons and skeletal muscle degeneration. An early event is thought to be denervation-induced muscle atrophy accompanied by alterations in mitochondrial activity and morphology within muscle. We now report that elevation of PGC-1α levels in muscles of mice that develop fatal paralysis from an ALS-causing SOD1 mutant elevates PGC-1α-dependent pathways throughout disease course. Mitochondrial biogenesis and activity are maintained through end-stage disease, accompanied by retention of muscle function, delayed muscle atrophy, and significantly improved muscle endurance even at late disease stages. However, survival was not extended. Therefore, muscle is not a primary target of mutant SOD1-mediated toxicity, but drugs increasing PGC-1α activity in muscle represent an attractive therapy for maintaining muscle function during progression of ALS.

Health and Fitness Benefits of a Resistance Training Intervention Performed in the Workplace

This study examined the effects of a workplace-based resistance training intervention on different health-, fitness-, and work-related measures in untrained men (bus drivers). The subjects were recruited from a bus company and divided into a training (n = 48) and control (n = 48) groups after initial prescreening. The training group performed a 24-week resistance training program, whereas the control group maintained their normal daily activities. Each group was assessed for body composition, blood pressure (BP), pain incidence, muscular endurance, and flexibility before and after the 24-week period. Work absenteeism was also recorded during this period and after a 12-week follow-up phase. In general, no body composition changes were identified in either group. In the training group, a significant reduction in BP and pain incidence, along with improvements in muscle endurance and flexibility were seen after 24 weeks (p < 0.05). There were no changes in these parameters in the control group, and the between-group differences were all significant (p < 0.05). A reduction in worker absenteeism rate was also noted in the training (vs. control) group during both the interventional and follow-up periods (p < 0.05). In conclusion, it was found that a periodized resistance training intervention performed within the workplace improved different aspects of health and fitness in untrained men, thereby potentially providing other work-related benefits. Thus, both employers and employees may benefit from the setup, promotion, and support of a work-based physical activity program involving resistance training.

Relationship between inspiratory muscle capacity and peak exercise tolerance in patients post-myocardial infarction

ObjectiveThe study objective was to evaluate inspiratory muscle endurance in patients post-myocardial infarction without respiratory muscle weakness and its correlation with peak exercise capacity. MethodsTen patients who recently had a myocardial infarction (recent infarction group [RIG]), 9 patients who less recently had a myocardial infarction (less recent infarction group [LIG]), and 12 healthy subjects (control group [CG]) underwent a cardiopulmonary exercise test and respiratory endurance protocol. Analysis of variance with post hoc Dunn comparisons was used to contrast performances on all tests, and Pearson's correlation was used to determine associations between variables. ResultsThe RIG presented lower maximal incremental pressure and oxygen consumption than the CG (P < .01). There was a positive correlation between peak oxygen uptake and both maximal inspiratory pressure (.68, P < .001) and maximal incremental pressure (.65, P < .001) in the RIG. ConclusionThe RIG showed lower maximal incremental pressure, which is related to peak exercise capacity. This novel relationship in functional capacity can indicate the need to improve muscle endurance in these patients even in the absence of inspiratory muscle weakness.

Exercise in Elderly Patients with Chronic Heart Failure in Primary Care: Effects on Physical Capacity and Health-Related Quality of Life

Chronic heart failure (CHF) limits exercise capacity which influences physical fitness and health-related quality of life (HRQoL). The aim was to determine the effects on physical capacity and HRQoL of an exercise programme in elderly patients with CHF in primary care. An exercise intervention was conducted as a prospective, longitudinal and controlled clinical study in primary care in elderly patients with CHF. Endurance exercise and resistance training were conducted as group-training at the primary care centre and as home training. Follow-up on physical capacity and HRQoL was done at 3, 6 and 12months. Exercise significantly improved muscle endurance in the intervention group (n=29, mean age 76.2years) compared to the control group (n=31, mean age 74.4years) at all follow-ups except for shoulder flexion right at 12months (shoulder abduction p=0.006, p=0.048, p=0.029; shoulder flexion right p=0.002, p=0.032, p=0.585; shoulder flexion left p=0.000, p=0.046, p=0.004). Six minute walk test improved in the intervention group at 3months (p=0.013) compared to the control group. HRQoL measured by EQ5D-VAS significantly improved in the intervention group at 3 and 12months (p=0.016 and p=0.034) and SF-36, general health (p=0.048) and physical component scale (p=0.026) significantly improved at 3months compared to the control group. This study shows that exercise conducted in groups in primary care and in the patients' homes could be used in elderly patients with CHF. The combination of endurance exercise and resistance training has positive effects on physical capacity. However, the minor effects in HRQoL need further verification in a study with a larger study population.

Acute Arginine Supplementation Fails to Improve Muscle Endurance Or Affect Blood Pressure Responses to Resistance Training

Dietary supplement companies claim that arginine supplements acutely enhance skeletal muscular endurance. The purpose of this study was to determine whether acute arginine α-ketoglutarate supplementation (AAKG) will affect local muscle endurance of the arm and shoulder girdle or the blood pressure (BP) response to anaerobic exercise. Twelve trained college-aged men (22.6 ± 3.8 years) performed 2 trials of exercise separated by at least 1 week. At 4 hours before, and 30 minutes before exercise, a serving of an AAKG supplement (3,700 mg arginine alpha-ketoglutarate per serving) or placebo was administered. Resting BP was assessed pre-exercise after 16 minutes of seated rest, and 5 and 10 minutes postexercise. Three sets each of chin-ups, reverse chin-ups, and push-ups were performed to exhaustion with 3 minutes of rest between each set. Data were analyzed using repeated-measures analysis of variance and paired t-tests. The AAKG supplementation did not improve muscle endurance or significantly affect the BP response to anaerobic work. Subjects performed fewer total chin-ups (23.75 ± 6.38 vs. 25.58 ± 7.18) and total trial repetitions (137.92 ± 28.18 vs. 141.08 ± 28.57) in the supplement trial (p ≤ 0.05). Subjects executed fewer reverse chin-ups (5.83 ± 1.85 vs. 6.75 ± 2.09) during set 2 after receiving the supplement as compared to the placebo (p < 0.05). Because AAKG supplementation may hinder muscular endurance, the use of these supplements before resistance training should be questioned.

Effect of Linear Polarized Near-infrared Light Irradiation and Light Exercise on Muscle Performance

This study aimed to determine the effect of active warm-up by local muscle light exercise and passive warm-up by polarized light irradiation on skin and muscle temperatures and forearm muscle performance (muscle strength, power, endurance, and controlled force-exertion). Ten healthy males performed various grip tests before and after active (local muscle light exercise) and passive (linear polarized near-infrared light irradiation) warm-ups. An active warm-up involved intermittent gripping exercise (contraction: 1 second and relaxation: 1 second) for 10 minutes using a sponge. A passive warm-up consisted of polarized light irradiation to the forearm (superficial digital flexor) for 10 minutes (irradiation: 5 seconds and rest: 1 second). Skin and muscle temperatures were measured during both warm-ups. Skin and muscle temperatures increased significantly after 5 minutes of local muscle light exercise and after 10 minutes of polarized light irradiation. Temperatures were significantly higher after 6 minutes of local muscle light exercise than after 6 minutes of polarized light irradiation. There were no significant differences of muscle strength, power, and controlled force-exertion before and after either warm-up. Average force outputs in all conditions significantly decreased with exertion time, and at 30, 60, 90, and 120 seconds they were higher in both warm-up conditions than in the non-warm-up condition. In conclusion, both warm-ups may contribute to improve muscle endurance performance in the decreasing force phase.

Exercise effects in patients with adult idiopathic inflammatory myopathies

To give an update on recent findings on effects of exercise in patients with adult inflammatory myopathies. Although responding to treatment, a majority of patients with polymyositis and dermatomyositis develop sustained disability. The reason for this is not clear. However, a recent study further supports the hypothesis of hypoxia in muscle tissue as a contributor to muscle weakness. The percentage of type I oxygen-dependent muscle fibers increased after a 12-week submaximal home exercise program along with improved muscle endurance in patients with chronic polymyositis or dermatomyositis. Creatine supplements in addition to the same home exercise program are more beneficial than exercise alone in patients with chronic polymyositis or dermatomyositis. Patients with chronic disease tolerate intensive resistance training resulting in improved muscle strength and muscle endurance. This 7-week exercise study also reported reduced disease activity and possibly even reduced muscle inflammation. These recent studies are in line with earlier ones further supporting safety and efficacy of exercise in patients with polymyositis or dermatomyositis. There is an urgent need for larger randomized controlled trials also including patients with inclusion body myositis to further increase knowledge of disease mechanisms causing disability, exercise effects, and what exercise program is most efficient in patients with different entities of idiopathic inflammatory myopathies.

Effect of betaine supplementation on power performance and fatigue

BackgroundThe purpose of this study was to examine the efficacy of 15 days of betaine supplementation on muscle endurance, power performance and rate of fatigue in active college-aged men.MethodsTwenty-four male subjects were randomly assigned to one of two groups. The first group (BET; 20.4 ± 1.3 years; height: 176.8 ± 6.6 cm; body mass: 77.8 ± 13.4 kg) consumed the supplement daily, and the second group (PL; 21.4 ± 4.7 years; height: 181.3 ± 5.9 cm; body mass: 83.3 ± 5.2 kg) consumed a placebo. Subjects were tested prior to the onset of supplementation (T1) and 7 (T2) and 14 days (T3) following supplementation. Each testing period occurred over a 2-day period. During day one of testing subjects performed a vertical jump power (VJP) and a bench press throw (BPT) power test. In addition, subjects were required to perform as many repetitions as possible with 75% of their 1-RM in both the squat and bench press exercises. Both peak and mean power was assessed on each repetition. On day two of testing subjects performed two 30-sec Wingate anaerobic power tests (WAnT), each test separated by a 5-min active rest.ResultsNo differences were seen at T2 or T3 in the repetitions performed to exhaustion or in the number of repetitions performed at 90% of both peak and mean power between the groups in the bench press exercise. The number of repetitions performed in the squat exercise for BET was significantly greater (p < 0.05) than that seen for PL at T2. The number of repetitions performed at 90% or greater of peak power in the squat exercise was significantly greater for BET at both T2 and T3 than PL. No differences in any power assessment (VJP, BPT, WAnT) was seen between the groupsConclusionTwo-weeks of betaine supplementation in active, college males appeared to improve muscle endurance of the squat exercise, and increase the quality of repetitions performed.

Qigong Improving Physical Status in Middle-Aged Women

Regular exercise has been shown to benefit its practitioners and prevent and control diseases. Muscle/Tendon Change Classic (MTCC) qigong, characterized by simple, slow, and full-body exercise, is appropriate for the middle-age population. This study aims to evaluate the effect of the MTCC qigong program in improving physical status for middle-aged women. A quasi-experimental design was used. The experimental group (n = 37) received an 8-week MTCC qigong program, whereas the control group (n = 34) received none. Physiological parameters of muscular performance, body composition, and bone strength were measured before and after the program. The average age was 49 +/- 4.13 years for the experimental group and 50 +/- 4.74 years for the control group. The demographic characteristics were homogeneous between the two groups. There were statistically significant differences between the two groups in muscular endurance, body fat, waist-to-hip ratio, and body mass index at the completion of 8-week MTCC qigong program. The MTCC qigong could improve muscle endurance and body composition but not bone strength for middle-aged women, thereby demonstrating the qigong practice has certain health-preserving effects on women in this stage of life.

Effects of Two Types of Neuromuscular Electrical Stimulation Training on Vertical Jump Performance

This study examined the effects of different types of neuromuscular electrical stimulation (NMES) programs on vertical jump performance. Twenty seven healthy trained male students in sports-sciences were recruited and randomized into three groups. The control group (C group, n = 8) did not perform NMES training. Two other groups underwent 3 training sessions a week over 5 weeks on the quadriceps femoris muscle [F group (n = 9): stimulation with an 80 Hz current for 15 min for improving muscle strength; E group (n = 10): stimulation with a 25 Hz current for 60 min for improving muscle endurance]. The height of the vertical jump was measured before NMES training (test 1), one week (test 2) and five weeks (test 3) after the end of the programs. The results showed that the height of the vertical jump significantly increased in both the F and E groups between tests 1 and 2 (5 cm and 3 cm respectively). Results of test 3 showed that both groups preserved their gains. A NMES training program destined to improve muscle endurance does not interfere on vertical jump performance. It can even durably enhance it in the same way as a NMES training program destined to improve muscle strength. Thus, to improve muscle endurance without deteriorating muscle power, sportsmen can use electrical stimulation.

The effect of beta-alanine supplementation on neuromuscular fatigue in elderly (55–92 Years): a double-blind randomized study

BackgroundAgeing is associated with a significant reduction in skeletal muscle carnosine which has been linked with a reduction in the buffering capacity of muscle and in theory, may increase the rate of fatigue during exercise. Supplementing beta-alanine has been shown to significantly increase skeletal muscle carnosine. The purpose of this study, therefore, was to examine the effects of ninety days of beta-alanine supplementation on the physical working capacity at the fatigue threshold (PWCFT) in elderly men and women.MethodsUsing a double-blind placebo controlled design, twenty-six men (n = 9) and women (n = 17) (age ± SD = 72.8 ± 11.1 yrs) were randomly assigned to either beta-alanine (BA: 800 mg × 3 per day; n = 12; CarnoSyn™) or Placebo (PL; n = 14) group. Before (pre) and after (post) the supplementation period, participants performed a discontinuous cycle ergometry test to determine the PWCFT.ResultsSignificant increases in PWCFT (28.6%) from pre- to post-supplementation were found for the BA treatment group (p < 0.05), but no change was observed with PL treatment. These findings suggest that ninety days of BA supplementation may increase physical working capacity by delaying the onset of neuromuscular fatigue in elderly men and women.ConclusionWe suggest that BA supplementation, by improving intracellular pH control, improves muscle endurance in the elderly. This, we believe, could have importance in the prevention of falls, and the maintenance of health and independent living in elderly men and women.

Short-term progressive resistance exercise may not be effective at increasing wrist strength in people with tetraplegia: a randomised controlled trial

Is an 8-week progressive resistance exercise program effective for increasing strength in the wrist muscles of people with tetraplegia? Is it effective for improving muscle endurance and participants' perceptions about use of their hands for activities of daily living? Randomised controlled trial with concealed allocation, assessor blinding, and intention-to-treat analysis. Thirty-two people with tetraplegia and neurological weakness of their wrist flexor or extensor muscles. The wrist muscles of one randomly-chosen hand were trained 3 times a week for 8 weeks. The control group received no intervention. The primary outcome was strength measured as maximal voluntary isometric torque in Nm. The secondary outcomes were muscle endurance measured as fatigue resistance and participants' perceptions about use of their hands using the Canadian Occupational Performance Measure. The mean effect on maximal voluntary isometric torque was 0.2 Nm (95% CI -0.5 to 0.8). This represents an 8% increase of mean initial strength; less than the 20% deemed clinically worthwhile at the commencement of the study. The mean effect on fatigue resistance was 0.1 (95% CI 0.0 to 0.2). The mean effect on participants' perceptions of performance was -0.3 (95% CI -1.9 to 1.2) and satisfaction was -0.3 (95% CI -1.6 to 1.0). The results indicate that progressive resistance exercise has no effect on participants' perceptions about hand function. However, it is not yet clear whether progressive resistance exercise programs improve strength and endurance in muscles with neurologically-induced weakness following tetraplegia.

Effect of physical training on the proportion of slow‐twitch type I muscle fibers, a novel nonimmune‐mediated mechanism for muscle impairment in polymyositis or dermatomyositis

To compare muscle fiber type composition and muscle fiber area in patients with chronic polymyositis or dermatomyositis and healthy controls, and to determine whether physical training for 12 weeks could alter these muscle characteristics. Muscle fiber type composition and muscle fiber area were investigated by biochemical and immunohistochemistry techniques in repeated muscle biopsy samples obtained from 9 patients with chronic myositis before and after a 12-week exercise program and in healthy controls. Muscle performance was evaluated by the Functional Index (FI) in myositis and by the Short Form 36 (SF-36) quality of life instrument. Before exercise, the proportion of type I fibers was lower (mean +/- SD 32% +/- 10%) and the proportion of type IIC fibers was higher (3% +/- 3%) in patients compared with healthy controls. After exercise, percentage of type I fiber increased to 42% +/- 13% (P < 0.05), and type IIC decreased to 1% +/- 1%. An exercise-induced 20% increase of the mean fiber area was also observed. The functional capacity measured by the FI in myositis and the physical functioning subscale of the SF-36 increased significantly. Improved physical functioning was positively correlated with the proportion of type I fibers (r = 0.88, P < 0.01) and type II muscle fiber area (r = 0.70, P < 0.05). Low muscle endurance in chronic polymyositis or dermatomyositis may be related to a low proportion of oxidative, slow-twitch type I fibers. Change in fiber type composition and increased muscle fiber area may contribute to improved muscle endurance and decreased muscle fatigue after a moderate physical training program.

Improved isometric force endurance after transcranial direct current stimulation over the human motor cortical areas

Neuromuscular fatigue is the exercise-dependent decrease in the ability of muscle fibres to generate force. To investigate whether manipulation of brain excitability by transcranial direct current stimulation (tDCS; 1.5 mA, 10 min, 0.026 C/cm(2)) modulates neuromuscular fatigue, we evaluated the effect of brain polarization over the right motor areas of the cerebral cortex of healthy subjects on the endurance time for a submaximal isometric contraction of left elbow flexors. In 24 healthy volunteers the study protocol comprised an assessment of the maximum voluntary contraction (MVC) for the left elbow flexors and a fatiguing isometric contraction (35% of MVC), before and immediately after brain polarization. One hour elapsed between baseline (T0) and postconditioning (T1) evaluation. After tDCS, MVC remained unchanged from baseline (mean +/- SEM; anodal tDCS: T0, 154.4 +/- 18.07; T1, 142.8 +/- 16.62 N; cathodal tDCS: T0, 156 +/- 18.75; T1, 141.86 +/- 17.53 N; controls: T0, 148.8 +/- 6.64; T1, 137.6 +/- 7.36 N; P > 0.1). Conversely, endurance time decreased significantly less after anodal than after cathodal tDCS or no stimulation (-21.1 +/- 5.5%, -35.7 +/- 3.3% and -39.3 +/- 3.3%, respectively; P < 0.05). None of the evaluated electromyographic variables changed after tDCS. Anodal tDCS could improve endurance time by directly modulating motor cortical excitability, modulating premotor areas, decreasing fatigue-related muscle pain, increasing motivation and improving synergist muscle coupling. Our findings, showing that anodal tDCS over the motor areas of the cerebral cortex improves muscle endurance, open the way to increasing muscle endurance and decreasing muscle fatigue in normal (i.e. sports medicine) and pathological conditions.

Effects of dorsiflexor endurance exercises on foot drop secondary to multiple sclerosis: A pilot study

This is a pilot study to determine if endurance exercises for dorsiflexors will improve walking for people with foot drop secondary to MS, and if improvement in muscle endurance for persons with MS can be predicted based on the amount of central fatigue (CF) in the muscle. Five individuals with foot drop secondary to MS and five age-matched controls. The intervention was 4 sets of 10 isometric contractions, at 60% of MVC, 3X/week, 8 weeks. Pretests-posttests included a dorsiflexor endurance test with superimposed electrical stimulation to measure CF, and a gait assessment including measurement of dorsiflexion at initial contact. Two of 5 subjects with MS had significant improvement in muscle endurance in both legs and in dorsiflexor control during walking. Correlation between CF and improved endurance was not significant (r=-0.07). One of the subjects with significant improvement in endurance had a significant decrease in central activation failure. For individuals with foot drop secondary to MS, endurance exercises for the dorsiflexors can result in improved walking. CF may not be useful in predicting whether a muscle will improve in endurance with exercise. Improvement may result from either a peripheral training effect, a central learning effect, or both.

Surgical treatment of multiple knee ligament injuries in 44 patients: 2–8 years follow-up results

The purpose of the study was to evaluate the mid-term results of surgical treatment in different groups of patients with multiple knee ligament injuries. Review of our patients' records revealed that 48 acute and chronic patients were surgically treated for combined knee injury. Due to severe capsular damage in these injuries, open techniques were used. In our treatment protocol, avulsed ligaments and tears of the posterolateral and posteromedial corner were repaired if possible, whereas midsubstance tears of cruciate ligaments and chronic cases were reconstructed with autografts. Postoperatively, an accelerated program of rehabilitation was introduced, aiming to progressively mobilize the joint and improve muscle endurance. For the follow-up evaluation we designed a protocol composed of two parts. In the first part, anatomical lesions were recorded and in the second part, clinical evaluation was performed using the Lysholm score, the Tegner rating system, the IKDC evaluation form, and the KT1000. Student's t tests and chi-square tests were used for data analysis. Forty-eight patients (mean age 28.6+/-11.9 years; 41 males) were classified according to the specific anatomical structures involved. Group A included 12 anterior cruciate ligament (ACL) and medial structure injuries, group B included 11 ACL or posterior cruciate ligament (PCL) ruptures combined with posterolateral injuries, and group C consisted of 25 knee dislocations (ACL and PCL ruptures which might be combined with damage of the collateral ligaments). Thirty-eight patients were surgically treated during the acute phase and ten patients were treated chronically. Forty-four patients (91.6%) were followed up at a mean of 51.3+/-29.9 months. Average Lysholm score was 87+/-12.3; average Tegner score was 5.09+/-2.19 before accident and 4.34+/-2.12 in re-examination; IKDC score was A in 10 cases, B in 22, C in 6, and D in 6. The mean range of motion was 129.9 degrees +/-12.5 degrees . The average loss of extension and flexion were 1.6 degrees +/-2.5 degrees and 7.6 degrees +/-7.9 degrees , respectively. The side-to-side difference in corrected anterior and posterior translation in quadriceps neutral angle and in anterior translation in 30 degrees angle was <3 mm for about 65% of our patients. Surgical treatment of multiple knee ligament injuries, using autografts, provided satisfactory stability, range of motion, and subjective functional results. However, despite the improvement of the quality of life, the preinjury patients' activity level was not fully obtained in re-examination. Patients underwent surgical treatment during the acute phase had better scores in several points, but finally there was no statistical significance between acute and chronic patients. Moreover, no statistically significant differences were observed among the groups with specific damaged anatomical structures.

Effects of nicotine on rat sternohyoid muscle contractile properties

Obstructive sleep apnoea (OSA) is a major clinical disorder characterised by recurring episodes of pharyngeal collapse during sleep. At present, there remains no satisfactory treatment for OSA. Pharmacological therapies as a potential treatment for the disorder are an attractive option and include agents that increase the contractility of the pharyngeal muscles. The aim of the present study was to examine the effects of nicotine on upper airway muscle contractile properties. In vitro isometric contractile properties were determined using strips of rat sternohyoid muscle in physiological salt solution containing nicotine (0-100 microg/ml) at 25 degrees C. Isometric twitch and tetanic tension, contraction time, half-relaxation time and tension-frequency relationship were determined by electrical field stimulation with platinum electrodes. Fatigue was induced by stimulation at 40 Hz with 300 ms trains at a frequency of 0.5 Hz for 5 min. Nicotine at a concentration of 1 microg/ml was associated with a significant increase in sternohyoid muscle specific tension compared to control data. Dose-dependent increases in contractile tension were not observed. Nicotine had effects on tension-frequency relationship and endurance properties of the sternohyoid muscle at some but not all doses. A leftward shift in the tension-frequency relationship was observed at low stimulus frequencies (20-30 Hz) for nicotine at a concentration of 1 and 5 microg/ml and a significant increase in fatigue resistance was observed with nicotine at a concentration of 10 microg/ml. As fatigue of the upper airway muscles has been implicated in obstructive airway conditions, a pharmacological agent that improves muscle endurance may prove useful as a potential treatment for such disorders. Therefore, further studies of the effects of nicotinic agonists on upper airway function are warranted.