The relative benefits of endurance and strength training on the metabolic factors and muscle function of people with type 2 diabetes mellitus

Objective: To compare the effects of a 4-month strength training (ST) versus aerobic endurance training (ET) program on metabolic control, muscle strength, and cardiovascular endurance in subjects with type 2 diabetes mellitus (T2D). Design: Randomized controlled trial. Setting: Large public tertiary hospital. Participants: Twenty-two T21) participants (I I men, I I women; mean age +/- standard error, 56.2 +/- 1.1 y; diabetes duration, 8.8 +/- 3.5y) were randomized into a 4-month ST program and 17 T2D participants (9 men, 8 women; mean age, 57.9 +/- 1.4y; diabetes duration, 9.2 +/- 1.7y) into a 4-month ET program. Interventions: ST (up to 6 sets per muscle group per week) and ET (with an intensity of maximal oxygen consumption of 60% and a volume beginning at 15min and advancing to a maximum of 30min 3X/wk) for 4 months. Main Outcome Measures: Laboratory tests included determinations of blood glucose, glycosylated hemoglobin (Hb A(1c)), insulin, and lipid assays. Results: A significant decline in Hb A, was only observed in the ST group (8.3% +/- 1.7% to 7.1% +/- 0.2%, P=.001). Blood glucose (204 +/- 16mg/dL to 147 +/- 8mg/dL, P <.001) and insulin resistance (9.11 +/- 1.51 to 7.15 +/- 1.15, P=.04) improved significantly in the ST group, whereas no significant changes were observed in the ET group. Baseline levels of total cholesterol (207 +/- 8mg/dL to 184 +/- 7mg/dL, P <.001), low-density lipoprotein cholesterol (120 +/- 8mg/dL to 106 +/- 8mg/dL, P=.001), and triglyceride levels (229 +/- 25mg/dL to 150 +/- 15mg/dL, P=.001) were significantly reduced and high-density lipoprotein cholesterol (43 +/- 3mg/dL to 48 +/- 2mg/dL, P=.004) was significantly increased in the ST group; in contrast, no such changes were seen in the ET group. Conclusions: ST was more effective than ET in improving glycemic control. With the added advantage of an improved lipid profile, we conclude that ST may play an important role in the treatment of T2D.

Changes in inflammatory mediators following eccentric exercise of the elbow flexors

The aims of this study were to examine the plasma concentrations of inflammatory mediators including cytokines induced by a single bout of eccentric exercise and again 4 weeks later by a second bout of eccentric exercise of the same muscle group. Ten untrained male subjects performed two bouts of the eccentric exercise involving the elbow flexors (6 sets of 5 repetitions) separated by four weeks. Changes in muscle soreness, swelling, and function following exercise were compared between the bouts. Blood was sampled before, immediately after, 1 h, 3 h, 6 h, 24 h (1 d), 48 h (2 d), 72 h (3 d), 96 h (4 d) following exercise bout to measure plasma creatine kinase (CK) activity, plasma concentrations of myoglobin (Mb), interleukin (IL)-1 beta, IL-1 receptor antagonist (IL-1ra), IL-4, IL-6, IL-8, IL-10, IL-12p40, tumor necrosis factor (TNF)-alpha, granulocyte colony-stimulating factor (G-CSF), myeloperoxidase (MPO), prostaglandin E-2 (PGE(2)), heat shock protein (HSP) 60 and 70. After the first bout, muscle soreness increased significantly, and there was also significant increase in upper arm circumference; muscle function decreased and plasma CK activity and Mb concentration increased significantly. These changes were significantly smaller after the second bout compared to the first bout, indicating muscle adaptation to the repeated bouts of the eccentric exercise. Despite the evidence of greater muscle damage after the first bout, the changes in cytokines and other inflammatory mediators were quite minor, and considerably smaller than that following endurance exercise. These results suggest that eccentric exercise-induced muscle damage is not associated with the significant release of cytokines into the systemic circulation. After the first bout, plasma G-CSF concentration showed a small but significant increase, whereas TNF-alpha and IL-8 showed significant decreases compared to the pre-exercise values. After the second bout, there was a significant increase in IL-10, and a significant decrease in IL-8. In conclusion, although there was evidence of severe muscle damage after the eccentric exercise, this muscle damage was not accompanied by any large changes in plasma cytokine concentrations. The minor changes in systemic cytokine concentration found in this study might reflect more rapid clearance from the circulation, or a lack of any significant metabolic or oxidative demands during this particular mode of exercise. In relation to the adaptation to the muscle damage, the anti-inflammatory cytokine IL-10 might work as one of the underlying mechanisms of action.

Adaptation to chronic eccentric exercise in humans: the influence of contraction velocity

We compared changes in muscle fibre composition and muscle strength indices following a 10 week isokinetic resistance training programme consisting of fast (3.14 rad(.)s(-1)) or slow (0.52 rad(.)s(-1)) velocity eccentric muscle contractions. A group of 20 non-resistance trained subjects were assigned to a FAST (n = 7), SLOW (n = 6) or non-training CONTROL (n = 7) group. A unilateral training protocol targeted the elbow flexor muscle group and consisted of 24 maximal eccentric isokinetic contractions (four sets of six repetitions) performed three times a week for 10 weeks. Muscle biopsy samples were obtained from the belly of the biceps brachii. Isometric torque and concentric and eccentric torque at 0.52 and 3.14 rad(.)s(-1) were examined at 0, 5 and 10 weeks. After 10 weeks, the FAST group demonstrated significant [mean (SEM)] increases in eccentric [29.6 (6.4)%] and concentric torque [27.4 (7.3) %] at 3.14 rad(.)s(-1), isometric torque [21.3 (4.3)%] and eccentric torque [25.2 (7.2) %] at 0.52 rad(.)s(-1). The percentage of type I fibres in the FAST group decreased from [53.8 (6.6)% to 39.1 (4.4)%] while type lib fibre percentage increased from [5.8 (1.9)% to 12.9 (3.3)%; P < 0.05]. In contrast. the SLOW group did not experience significant changes in muscle fibre type or muscle torque. We conclude that neuromuscular adaptations to eccentric training stimuli may be influenced by differences in the ability to cope with chronic exposure to relatively fast and slow eccentric contraction velocities. Possible mechanisms include greater cumulative damage to contractile tissues or stress induced by slow eccentric muscle contractions.

Dynamic training volume: A construct of both time under tension and volume load

The purpose of this study was to investigate the effects of three different weight training protocols, that varied in the way training volume was measured, on acute muscular fatigue. Ten resistance-trained males performed all three protocols which involved dynamic constant resistance exercise of the elbow flexors. Protocol A provided a standard for the time the muscle group was under tension (TUT) and volume load (VL), expressed as the product of the total number of repetitions and the load that was lifted. Protocol B involved 40% of the TUT but the same VL compared to protocol A; protocol C was equated with protocol A for TUT but only involved 50% of the VL. Fatigue was assessed by changes in maximum voluntary isometric force and integrated electromyography (iEMG) between the pre- and post-training protocols. The results of the study showed that, when equated for VL, greater TUT produced greater overall muscular fatigue ( p

MR morphometry of posterior tibialis muscle in adult acquired flat foot

We conducted magnetic resonance imaging of the posterior tibial (PT) and flexor digitorum longus (FDL) muscle bellies in 12 patients undergoing surgical treatment for unilateral posterior tibial tendon (PTT) dysfunction. All patients had atrophy of the PT muscle compared to the normal leg (mean 10.7%, p=0.008). In those patients with a complete rupture of PTT there was replacement of the PT muscle by fatty infiltration. Conversely, the FDL muscle showed a compensatory hypertrophy (mean 17.2%, p

Leg muscle recruitment in highly trained cyclists

In this study, we examined patterns of leg muscle recruitment and co-activation, and the relationship between muscle recruitment and cadence, in highly trained cyclists. Electromyographic (EMG) activity of the tibialis anterior, tibialis posterior, peroneus longus, gastrocnemius lateralis and soleus was recorded using intramuscular electrodes, at individual preferred cadence, 57.5, 77.5 and 92.5 rev.min(-1). The influence of electrode type and location on recorded EMG was also investigated using surface and dual intramuscular recordings. Muscle recruitment patterns varied from those previously reported, but there was little variation in muscle recruitment between these highly trained cyclists. The tibialis posterior, peroneus longus and soleus were recruited in a single, short burst of activity during the downstroke. The tibialis anterior and gastrocnemius lateralis were recruited in a biphasic and alternating manner. Contrary to existing hypotheses, our results indicate little co-activation between the tibialis posterior and peroneus longus. Peak EMG amplitude increased linearly with cadence and did not decrease at individual preferred cadence. There was little variation in patterns of muscle recruitment or co-activation with changes in cadence. Intramuscular electrode location had little influence on recorded EMG. There were significant differences between surface and intramuscular recordings from the tibialis anterior and gastrocnemius lateralis, which may explain differences between our findings and those of previous studies.

Involuntary glottal closure during inspiration in muscle tension dysphonia

Objective/Hypothesis: The purpose of this study was to examine respiratory function in a group of patients with muscle tension dysphonia (MTD) Design: Cross-sectional analytical study. Methods: Participants included 15 people with a diagnosis of MTD referred to speech pathology for management of their voice disorder, fiberoptic evidence of glottal or supraglottic constriction during phonation with or without posterior chink, or bowing combined and deviation in perceptual voice quality. A second group of 15 participants with no history of voice disorder served as healthy controls,. Baseline pulmonary function test measures included forced expiratory volume in the first second (FEV1), FVC, FEF25 to 75, FIF50, FEV1/FVC, ratio and FEF50/FIF50 ratio. Hypertonic saline challenge test measures included FEV1 and FIF50 after provocation, close response slope, and provocation dose. Results: Compared with healthy controls, participants with MTD demonstrated a higher prevalence of glottal constriction during inspiration after provocation with nebulized hypertonic saline as demonstrated by a reduction in FIF50 after the hypertonic saline challenge. There was no significant difference between the MTD and healthy control groups in baseline pulmonary function testing. Participants with MTD demonstrated a higher prevalence than healthy controls of abnormal glottic closure during inspiration similar to paradoxical vocal fold movement (PVFM). This suggests that they either had previously undiagnosed coexisting PVFM or that the condition of MTD could be expanded to include descriptions of aberrant glottic function during respiration. This study enhances the understanding of PVFM and MTD by combining research advances made in the fields of otolaryngology and respiratory medicine.

Vascular smooth muscle and arterial calcification

Smooth muscle cultures can calcify under certain circumstances. As a model system these cultures therefore provide information on why calcification occurs in atherosclerotic plaques. Whether all smooth muscle cells (under certain conditions), or only specific populations, can produce this mineralization has not been resolved. Demer's group has cloned calcifying vascular cells from subcultured bovine aorta and studied them in detail. They have speculated on whether the cells are smooth muscle which have altered in phenotype, or whether they are derived from a stem cell population within the artery wall. The article argues that while the normal process of smooth muscle phenotypic modulation seen in arterial repair could account for the observations, this view may be two simplistic considering the complex nature of the artery wall. Certainly there is evidence for heterogeneity of smooth muscle cells in the artery wall and recent evidence suggests that stem cells can circulate in the blood and repopulate tissues. Further studies are required to resolve the important question as to the origin of cells which produce mineralization in atheroma.

Tension regulation during lengthening and shortening actions of the human soleus muscle

In the present study we investigated tension regulation in the human soleus (SOL) muscle during controlled lengthening and shortening actions. Eleven subjects performed plantar flexor efforts on an ankle torque motor through 30 degrees of ankle displacement (75 degrees-105 degrees internal ankle angle) at lengthening and shortening velocities of 5, 15 and 30 degrees s(-1). To isolate the SOL from the remainder of the triceps surae, the subject's knee was flexed to 60 degrees during all trials. Voluntary plantar flexor efforts were performed under two test conditions: (1) maximal voluntary activation (MVA) of the SOL, and (2) constant submaximal voluntary activation (SVA) of the SOL. SVA trials were performed with direct visual feedback of the SOL electromyogram (EMG) at a level resulting in a torque output of 30% of isometric maximum. Angle-specific (90 degrees ankle angle) torque and EMG of the SOL, medial gastrocnemius (MG) and tibialis anterior (TA) were recorded. In seven subjects from the initial group, the test protocol was repeated under submaximal percutaneous electrical activation (SEA) of SOL (to 30% isometric maximal effort). Lengthening torques were significantly greater than shortening torques in all test conditions. Lengthening torques in MVA and SVA were independent of velocity and remained at the isometric level, whereas SEA torques were greater than isometric torques and increased at higher lengthening velocities. Shortening torques were lower than the isometric level for all conditions. However, whereas SVA and SEA torques decreased at higher velocities of shortening, MVA torques were independent of velocity. These results indicate velocity- and activation-type-specific tension regulation in the human SOL muscle.

Muscle fibre types and size distribution in sub-antarctic notothenioid fishes

The presumptive tonic muscles fibres of Cottoperca gobio, Champsocephalus esox, Harpagifer bispinis, Eleginops maclovinus, Patagonothen tessellata, P. cornucola and Paranotothenia magellanica stained weakly or were unstained for glycogen, lipid, succinic dehydrogenase (SDHase) and myosin ATPase (mATPase) activity. Slow, intermediate and fast twitch muscle fibres, distinguished on the basis of the pH stability of their mATPases, showed intense, moderate and low staining activity for SDHase, respectively. Slow fibres were the major component of the pectoral fin adductor profundis muscle. The proportion of different muscle fibre types varied from the proximal to distal end of the muscle, but showed relatively little variation between species. The myotomes contained a lateral superficial strip of red muscle composed of presumptive tonic, slow twitch and intermediate fibres, thickening to a major wedge at the horizontal septum. All species also had characteristic secondary dorsal and ventral wedges of red muscle. The relative abundance and localization of muscle fibre types in the red muscle varied between species and with body size in the protandric hermaphrodite E. maclovinus. The frequency distribution of diameters for fast twitch muscle fibres, the major component of deep white muscle, was determined in fish of a range of body sizes. The absence of fibres <20 mu m diameter was used as a criterion for the cessation of muscle fibre recruitment. Fibre recruitment had stopped in P, tessellata of 13.8 cm L-T and E, maclovinus of 32.8 cm L-T, equivalent to 49 and 36.5% of their recorded maximum sizes respectively. As a result in 20-cm P. tessellata, the maximum fibre diameter was 300 mu m and 36% of fibres were in excess of 200 mu m The unusually large maximum fibre diameter, the general arrangement of the red muscle layer and the extreme pH lability of the mATPase of fast twitch fibres are all common characters of the sub-Antarctic and Antarctic Notothenioids, including Cottoperca gobio, the suggested sister group to the Notothenidae. (C) 2000 The Fisheries Society of the British Isles.

Multifidus muscle recovery is not automatic after resolution of acute, first-episode low back pain

Study Design. A clinical study was conducted on 39 patients with acute, first-episode, unilateral low back pain and unilateral, segmental inhibition of the multifidus muscle. Patients were allocated randomly to a control or treatment group. Objectives. To document the natural course of lumbar multifidus recovery and to evaluate the effectiveness of specific, localized, exercise therapy on muscle recovery. Summary of Background Data. Acute low back pain usually resolves spontaneously, but the recurrence rate is high. Inhibition of multifidus occurs with acute, first-episode, low back pain, and pathologic changes in this muscle have been linked with poor outcome and recurrence of symptoms. Methods. Patients in group 1 received medical treatment only. Patients in group 2 received medical treatment and specific, localized, exercise therapy. Outcome measures for both groups included 4 weekly assessments of pain, disability, range of motion, and size of the multifidus cross-sectional area. Independent examiners were blinded to group allocation. Patients were reassessed at a 10-week follow-up examination. Results. Multifidus muscle recovery was not spontaneous on remission of painful symptoms in patients in group 1. Muscle recovery was more rapid and more complete in patients in group 2 who received exercise therapy (P = 0.0001). Other outcome measurements were similar for the two groups at the 4-week examination. Although they resumed normal levels of activity, patients in group 1 still had decreased multifidus muscle size at the 10-week follow-up examination. Conclusions. Multifidus muscle recovery is not spontaneous on remission of painful symptoms. Lack of localized, muscle support may be one reason for the high recurrence rate of low back pain following the initial episode.

Vascular smooth muscle relaxation mediated by nitric oxide donors: a comparison with acetylcholine, nitric oxide and nitroxyl ion

I Vasorelaxant properties of three nitric oxide (NO) donor drugs (glyceryl trinitrate, sodium nitroprusside and spermine NONOate) in mouse aorta (phenylephrine pre-contracted) were compared with those of endothelium-derived NO (generated with acetylcholine), NO free radical (NO; NO gas solution) and nitroxyl ion (NO-; from Angeli's salt). 2 The soluble guanylate cyclase inhibitor, ODQ (1H-(1,2,4-)oxadiazolo(4,3-a)-quinoxalin-1-one; 0.3, 1 and 10 muM), concentration-dependently inhibited responses to all agents. 10 muM ODQ abolished responses to acetylcholine and glyceryl trinitrate, almost abolished responses to sodium nitroprusside but produced parallel shifts (to a higher concentration range; no depression in maxima) in the concentration-response curves for NO gas solution, Angeli's salt and spermine NONOate. 3 The NO scavengers, carboxy-PTIO, (2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-indazoline-1-oxyl-3-oxide; 100 muM) and hydroxocobalamin (100 muM), both inhibited responses to NO gas solution and to the three NO donor drugs, but not Angeli's salt. Hydroxocobalamin, but not carboxy-PTIO, also inhibited responses to acetylcholine. 4 The NO- inhibitor, L-cysteine (3 mm), inhibited responses to Angeli's salt, acetylcholine and the three NO donor drugs, but not NO gas solution. 5 The data suggest that, in mouse aorta, responses to all three NO donors involve (i) activation of soluble guanylate cyclase, but to differing degrees and (ii) generation of both NO and NO-. Glyceryl trinitrate and sodium nitroprusside, which generate NO following tissue bioactivation, have profiles resembling the profile of endothelium-derived NO more than that of exogenous NO. Spermine NONOate, which generates NO spontaneously outside the tissue, was the drug that most closely resembled (but was not identical to) exogenous NO.

Short-term beta-hydroxy-beta-methylbutyrate supplementation does not reduce symptoms of eccentric muscle damage

Purpose: We examined the effects of short-term beta -hydroxy-beta -methylbutyrate (HIM) supplementation on symptoms of muscle damage following an acute bout of eccentric exercise. Methods: Non-resistance trained subjects were randomly assigned to a HMB supplement group (HMB, 40mg/kg bodyweight/day, n = 8) or placebo group (CON, n = 9). Supplementation commenced 6 days prior to a bout of 24 maximal isokinetic eccentric contractions of the elbow flexors and continued throughout post-testing. Muscle soreness, upper arm girth, and torque measures were assessed pre-exercise, 15 min post-exercise, and 1, 2, 3, 4, 7, and 10 days post-exercise. Results: No pre-test differences between HMB and CON groups were identified, and both performed a similar amount of eccentric work during the main eccentric exercise bout (p > .05). HMB supplementation had no effect on swelling, muscle soreness, or torque following the damaging eccentric exercise bout (p > .05). Conclusion: Compared to a placebo condition, short-term supplementation with 40mg/kg bodyweight/day of HMB had no beneficial effect on a range of symptoms associated with eccentric muscle damage. If HMB can produce an ergogenic response, a longer pre-exercise supplementation period may be necessary.