Blood flow after contraction and cuff occlusion is reduced in subjects with muscle soreness after eccentric exercise.

Delayed onset muscle soreness (DOMS) occurs within 1-2 days after eccentric exercise, but the mechanism mediating hypersensitivity is unclear. This study hypothesized that eccentric exercise reduces the blood flow response following muscle contractions and cuff occlusion, which may result in accumulated algesic substances being a part of the sensitization in DOMS. Twelve healthy subjects (five women) performed dorsiflexion exercise (five sets of 10 repeated eccentric contractions) in one leg, while the contralateral leg was the control. The maximal voluntary contraction (MVC) of the tibialis anterior muscle was recorded. Blood flow was assessed by ultrasound Doppler on the anterior tibialis artery (ATA) and within the anterior tibialis muscle tissue before and immediately after 1-second MVC, 5-seconds MVC, and 5-minutes thigh cuff occlusion. Pressure pain thresholds (PPTs) were recorded on the tibialis anterior muscle. All measures were done bilaterally at day 0 (pre-exercise), day 2, and day 6 (post-exercise). Subjects scored the muscle soreness on a Likert scale for 6 days. Eccentric exercise increased Likert scores at day 1 and day 2 compared with day 0 (P<.001). Compared with pre-exercise (day 0), reduced PPT (~25%, P<.002), MVC (~22%, P<.002), ATA diameter (~8%, P<.002), ATA post-contraction/occlusion blood flow (~16%, P<.04), and intramuscular peak blood flow (~23%, P<.03) were found in the DOMS leg on day 2 but not in the control leg. These results showed that eccentric contractions decreased vessel diameter, impaired the blood flow response, and promoted hyperalgesia. Thus, the results suggest that the blood flow reduction may be involved in the increased pain response after eccentric exercise.

Breaking up Prolonged Sitting does not Alter Postprandial Glycemia in Young, Normal-Weight Men and Women.

A randomized, controlled, cross-over study was used to investigate the effects of breaking up prolonged sitting with low intensity physical activity on postprandial blood glucose concentrations in healthy, young, normal-weight adults. 14 men (n=6) and women (n=8) were assigned to 2.5 h of prolonged sitting (CON) and 2.5 h of prolonged sitting with 2-min bouts of walking every 20 min (LIPA). After ingesting a standardized test drink, capillary blood was sampled every 10 min to establish a postprandial blood glucose profile. Based on individual glucose responses, peak blood glucose, time-to-peak glucose, and incremental area under the glucose curve (iAUC) were determined. Paired sample t-tests were used to detect differences between trials. Peak blood glucose (p=0.55) and iAUC (CON: 252 mmol·L-1·2.5 h-1 [163-340]; LIPA: 214 mmol·L-1·2.5 h-1 [146-282]; p=0.45) were not different between trials. Also, time-to-peak glucose was not different between LIPA and CON (p=0.37). Taking advantage of high temporal resolution blood glucose profiles, we showed that breaking up prolonged sitting with low-intensity physical activity does not alter the postprandial blood glucose response in young, healthy, normal-weight adults. Our results indicate that postprandial glycemic control is maintained during prolonged sitting in young, healthy adults.

High-intensity interval training alters ATP pathway flux during maximal muscle contractions in humans.

AIM: High-intensity interval training (HIT) results in potent metabolic adaptations in skeletal muscle; however, little is known about the influence of these adaptations on energetics in vivo. We used magnetic resonance spectroscopy to examine the effects of HIT on ATP synthesis from net PCr breakdown (ATPCK ), oxidative phosphorylation (ATPOX ) and non-oxidative glycolysis (ATPGLY ) in vivo in vastus lateralis during a 24-s maximal voluntary contraction (MVC). METHODS: Eight young men performed 6 sessions of repeated, 30-s 'all-out' sprints on a cycle ergometer; measures of muscle energetics were obtained at baseline and after the first and sixth sessions. RESULTS: Training increased peak oxygen consumption (35.8 ± 1.4 to 39.3 ± 1.6 mL min(-1) kg(-1) , P = 0.01) and exercise capacity (217.0 ± 11.0 to 230.5 ± 11.7 W, P = 0.04) on the ergometer, with no effects on total ATP production or force-time integral during the MVC. While ATP production by each pathway was unchanged after the first session, 6 sessions increased the relative contribution of ATPOX (from 31 ± 2 to 39 ± 2% of total ATP turnover, P < 0.001) and lowered the relative contribution from both ATPCK (49 ± 2 to 44 ± 1%, P = 0.004) and ATPGLY (20 ± 2 to 17 ± 1%, P = 0.03). CONCLUSION: These alterations to muscle ATP production in vivo indicate that brief, maximal contractions are performed with increased support of oxidative ATP synthesis and relatively less contribution from anaerobic ATP production following training. These results extend previous reports of molecular and cellular adaptations to HIT and show that 6 training sessions are sufficient to alter in vivo muscle energetics, which likely contributes to increased exercise capacity after short-term HIT.

Localization and quantification of muscle damage by magnetic resonance imaging following step exercise in young women.

Eccentric exercise affects muscles differentially according to intensity, duration, and previous exposure to the specific exercise activity. We used T2-weighted magnetic resonance imaging sequences to localize and quantify muscle damage following step exercise and to determine correlations between transverse relaxation time (T2) and other markers of muscle damage. Eight women performed two-step exercise bouts (30 min) separated by 8 weeks. Blood samples, MR scans, measurements of muscle strength, and muscle soreness were obtained immediately before, after, and up to 9 days after each bout. Resting muscle T2 (40.3+/-0.6 ms) increased exclusively in m. Adductor magnus (AM) in the thigh performing eccentric contractions and peaked 3 days after bout 1 (73.5+/-9.7 ms, P<0.05). Plasma creatine kinase (CK) activity peaked on day 3 after bout 1 and correlated with T2 in AM (r=0.96, P<0.001). After bout 2 CK and T2 were almost unaffected. This indicates that T2-weighted MRI can be applied to identify muscles from which enzymes are being released into the circulation.

Characterization of the active site of p21 ras by electron spin-echo envelope modulation spectroscopy with selective labeling: comparisons between GDP and GTP forms.

Selectively labeled samples of human H- or N-ras p21 ligated to MnIIGDP or MnIIGMPPNP were studied by electron spin-echo envelope modulation spectroscopy in order to define the protein environment around the divalent metal. We incorporated [4-13C]-labeled Asx into p21.MnIIGDP and found that the distance from the carboxyl 13C of Asp57 to MnII is approximately 4.1 A. Our result is consistent with indirect coordination of this residue to the metal. From a [2-2H]Thr-labeled sample, we estimate that the distance from the MnII ion to the 2H of Thr35 is at least 5.8 A. Thus, the only protein or nucleotide ligands to the metal appear to be Ser17 and the beta-phosphate of GDP, as previously reported [Larsen, R. G., Halkides, C. J., Redfield, A. G., & Singel, D. J. (1992b) J. Am. Chem. Soc. 114, 9608-9611]. In the 5'-guanylylimido diphosphate (GMPPNP) form of p21, Thr35 has been reported by X-ray crystallography to be a ligand of the metal via its hydroxyl group, and this residue appears to play a key role in the biologically important conformational change upon nucleotide substitution [Pai, E. F., Krengel, U., Petsko, G., Goody, R. S., Kabsch, W., & Wittinghofer, A. (1990) EMBO J. 9, 2351-2359]. The ESEEM spectrum of p21.MnIIGMPPNP labeled with [2-2H]Thr yields a MnII-2H distance of 4.9 A, a distance inconsistent with strong coordination. A sample of p21 in which the Thr residues were fully labeled with 13C and 15N yielded a value of 5.0 A for the distance from MnII to the amide nitrogen of Thr35, while the 13C signal is much smaller than expected if Thr35 were coordinated. A [15N]serine/glycine-labeled sample gives a distance to the amide 15N of Ser17 of 3.9 A, consistent with the X-ray structure; a [4-13C]-labeled Asx sample of p21 gives a distance of approximately 4 A between MnII and the label of Asp57, again implying indirect coordination. Both of these values are very similar to those found for the GDP form of the protein. The results for Thr35, however, reveal a structural difference between the GDP and GTP forms in the region of Thr35. In addition, the position of this residue is found to be different from the crystal structure and in a manner suggesting that the metal ligation of Thr35 does not drive the conformational change that accompanies nucleotide substitution.

[Regional anesthesia in emergency cesarean section. Quality of epidural and spinal anesthesia]. / Regionalanestesi ved akutt keisersnitt. Anestesikvalitet ved epidural- og spinalanestesi.

From 1987 to 1989, 97.8% of non-elective caesarean sections at Innherred general hospital were performed under regional anaesthesia (N = 271). A retrospective analysis showed that the mean time from giving the anaesthetic until start of surgery was 28.1 min. with epidural anaesthesia and 12.7 min. with spinal anaesthesia. Mean time was 25.9 and 9.3 min. respectively in cases of suspected asphyxia. In eight women primary anesthesia was unsuccessful; six received further spinal anaesthesia and two general anaesthesia. Regional anaesthesia is considered safe for the purpose, but in cases of serious asphyxia there is some controversy as to whether spinal or general anaesthesia is to be preferred.