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Carbohydrate Mouth Rinse Maintains Muscle Electromyographic Activity and Increases Time to Exhaustion during Moderate but not High-Intensity Cycling Exercise.
Bastos-Silva, VJ, Melo, Ade A, Lima-Silva, AE, Moura, FA, Bertuzzi, R, de Araujo, GG
Nutrients. 2016;(3):49
Abstract
The aim was to investigate the influence of a carbohydrate (CHO) mouth rinse on the vastus lateralis (VL) and rectus femoris (RF) electromyographic activity (EMG) and time to exhaustion (TE) during moderate (MIE) and high-intensity cycling exercise (HIE). Thirteen participants cycled at 80% of their respiratory compensation point and at 110% of their peak power output to the point of exhaustion. Before the trials and every 15 min during MIE, participants rinsed with the CHO or Placebo (PLA) solutions. The root mean square was calculated. CHO had no effect on the TE during HIE (CHO: 177.3 ± 42.2 s; PLA: 163.0 ± 26.7 s, p = 0.10), but the TE was increased during MIE (CHO: 76.6 ± 19.7 min; PLA: 65.4 ± 15.2 min; p = 0.01). The EMG activity in the VL was higher than PLA at 30 min (CHO: 10.5% ± 2.6%; PLA: 7.7% ± 3.3%; p = 0.01) and before exhaustion (CHO: 10.3% ± 2.5%; PLA: 8.0% ± 2.9%; p = 0.01) with CHO rinsing. There was no CHO effect on the EMG activity of RF during MIE or for VL and RF during HIE. CHO mouth rinse maintains EMG activity and enhances performance for MIE but not for HIE.
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Volumetric and functional evaluation of the gluteus maximus muscle after augmentation gluteoplasty using silicone implants.
Serra, F, Aboudib, JH, Neto, JIS, Cossich, VRA, Rodrigues, NCP, de Oliveira, KF, Marques, RG
Plastic and reconstructive surgery. 2015;(3):533e-541e
Abstract
BACKGROUND The gluteal muscles have been very important throughout the evolution of mankind for the adoption of the bipedal posture. Over the past 15 years, the intramuscular technique has become popular and has been improved, with enhanced results and reduced levels of postoperative complications. The insertion of gluteal implants within the musculature may be an intrinsic compression factor of these muscles. The objective of the present study was to evaluate the gluteus maximus function and its variation over a 12-month period after the insertion of the implant. METHODS This was a prospective, controlled, clinical study. All subjects were female patients, with anthropometric characteristics and body mass index within preset limits to establish similar groups. Isokinetic test gluteus computed tomographic scans and clinical nutritional assessment were conducted in four stages during the study period: preoperatively and 3, 6, and 12 months after surgery. RESULTS The study group presented 6.14 percent muscle atrophy to the left and 6.43 percent muscle atrophy to the right after the procedure. Muscle strength presented differences in hip flexion and adduction tests. CONCLUSIONS The gluteus maximus muscle presents atrophy secondarily to gluteal augmentation surgery with implants. Variations in gluteus maximus muscle strength should not be attributed primarily to the surgical procedure or to the implants; physiologic and multifactorial variations should also be considered. Strength and volume variations did not show a significant correlation. Gluteal augmentation with implants was effective in improving the waist-to-hip ratio and in changing the anthropometric pattern from android to gynoid. CLINICAL QUESTION/LEVEL OF EVIDENCE Therapeutic, II.
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Focal knee joint cooling increases the quadriceps central activation ratio.
Pietrosimone, BG, Ingersoll, CD
Journal of sports sciences. 2009;(8):873-9
Abstract
The objective of this study was to evaluate the effects of a 20-min focal knee joint cooling intervention on quadriceps central activation ratio (CAR) in healthy volunteers. A counterbalanced, cross-over study assessed the effects of a focal joint cooling intervention compared with a control condition 3-14 days apart. Eleven healthy volunteers (6 males, 5 females; age 25 +/- 5 years; height 1.71 +/- 0.1 m, mass 77 +/- 21 kg) were included in the final analysis. The joint cooling intervention consisted of two 1.5-litre ice bags applied to the knee joint for 20 min, in one of two counterbalanced sessions, completed 3-14 days apart. In the control session, participants sat quietly between the baseline and 20-min measurements. Quadriceps CAR was assessed at 70 degrees of knee flexion at four instants (baseline, 20, 30, and 45 min). There was a significant treatment x time interaction (F(3,30) = 5.9, P = 0.003) and post hoc analyses revealed that CAR was higher in the focal knee joint cooling session than the control session at 20 min (0.79 +/- 0.12 vs. 0.70 +/- 0.12; t(10) = 3.9, P = 0.003) and 45 min (0.77 +/- 0.10 vs. 0.69 +/- 0.12; t(10) = 3.1, P = 0.01). The CAR tended to be higher during the experimental session than the control session at 30 min (0.79 +/- 0.13 vs. 0.74 +/- 0.11; t(10) = 2.1, P = 0.07).Volitional activation increased following focal knee joint cooling in healthy volunteers.
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Higher skeletal muscle alpha2AMPK activation and lower energy charge and fat oxidation in men than in women during submaximal exercise.
Roepstorff, C, Thiele, M, Hillig, T, Pilegaard, H, Richter, EA, Wojtaszewski, JF, Kiens, B
The Journal of physiology. 2006;(Pt 1):125-38
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Abstract
5'AMP-activated protein kinase (AMPK) is an energy sensor activated by perturbed cellular energy status such as during muscle contraction. Activated AMPK is thought to regulate several key metabolic pathways. We used sex comparison to investigate whether AMPK signalling in skeletal muscle regulates fat oxidation during exercise. Moderately trained women and men completed 90 min bicycle exercise at 60% VO2peak. Both AMPK Thr172 phosphorylation and alpha2AMPK activity were increased by exercise in men (approximately 200%, P < 0.001) but not significantly in women. The sex difference in muscle AMPK activation with exercise was accompanied by an increase in muscle free AMP (approximately 164%, P < 0.01), free AMP/ATP ratio (159%, P < 0.05), and creatine (approximately 42%, P < 0.001) in men but not in women (NS), suggesting that lack of AMPK activation in women was due to better maintenance of muscle cellular energy balance compared with men. During exercise, fat oxidation per kg lean body mass was higher in women than in men (P < 0.05). Regression analysis revealed that a higher proportion of type 1 muscle fibres (approximately 23%, P < 0.01) and a higher capillarization (approximately 23%, P < 0.05) in women than in men could partly explain the sex difference in alpha2AMPK activity (r = -0.54, P < 0.05) and fat oxidation (r = 0.64, P < 0.05) during exercise. On the other hand, fat oxidation appeared not to be regulated via AMPK. In conclusion, during prolonged submaximal exercise at 60% VO2peak, higher fat oxidation in women cannot be explained by higher AMPK signalling but is accompanied by improved muscle cellular energy balance in women probably due to sex specific muscle morphology.
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Acute exercise and GLUT4 expression in human skeletal muscle: influence of exercise intensity.
Kraniou, GN, Cameron-Smith, D, Hargreaves, M
Journal of applied physiology (Bethesda, Md. : 1985). 2006;(3):934-7
Abstract
To examine the influence of exercise intensity on the increases in vastus lateralis GLUT4 mRNA and protein after exercise, six untrained men exercised for 60 min at 39 +/- 3% peak oxygen consumption (V(O2 peak)) (Lo) or 27 +/- 2 min at 83 +/- 2% V(O2 peak) (Hi) in counterbalanced order. Preexercise muscle glycogen levels were not different between trials (Lo: 408 +/- 35 mmol/kg dry mass; Hi: 420 +/- 43 mmol/kg dry mass); however, postexercise levels were lower (P < 0.05) in Hi (169 +/- 18 mmol/kg dry mass) compared with Lo (262 +/- 35 mmol/kg dry mass). Thus calculated muscle glycogen utilization was greater (P < 0.05) in Hi (251 +/- 24 mmol/kg) than in Lo (146 +/- 34). Exercise resulted in similar increases in GLUT4 gene expression in both trials. GLUT4 mRNA was increased immediately at the end of exercise (approximately 2-fold; P < 0.05) and remained elevated after 3 h of postexercise recovery. When measured 3 h after exercise, total crude membrane GLUT4 protein levels were 106% higher in Lo (3.3 +/- 0.7 vs. 1.6 +/- 0.3 arbitrary units) and 61% higher in Hi (2.9 +/- 0.5 vs. 1.8 +/- 0.5 arbitrary units) relative to preexercise levels. A main effect for exercise was observed, with no significant differences between trials. In conclusion, exercise at approximately 40 and approximately 80% V(O2 peak), with total work equal, increased GLUT4 mRNA and GLUT4 protein in human skeletal muscle to a similar extent, despite differences in exercise intensity and duration.
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6.
Ca2+-calmodulin-dependent protein kinase expression and signalling in skeletal muscle during exercise.
Rose, AJ, Kiens, B, Richter, EA
The Journal of physiology. 2006;(Pt 3):889-903
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Abstract
Ca2+ signalling is proposed to play an important role in skeletal muscle function during exercise. Here, we examined the expression of multifunctional Ca2+-calmodulin-dependent protein kinases (CaMK) in human skeletal muscle and show that CaMKII and CaMKK, but not CaMKI or CaMKIV, are expressed. Furthermore, the effect of exercise duration and intensity on skeletal muscle CaMKII activity and phosphorylation of downstream targets was examined. Eight healthy men exercised at approximately 67% of peak pulmonary O2 uptake(VO2peak) with muscle samples taken at rest and after 1, 10, 30, 60 and 90 min of exercise. Ten other men exercised for three consecutive 10 min bouts at 35%, 60% and 85% VO2peak with muscle samples taken at rest, at the end of each interval and 30 min post-exercise. There was a rapid and transient increase in autonomous CaMKII activity and CaMKII phosphorylation at Thr287 in skeletal muscle during exercise. Furthermore, the phosphorylation of phospholamban (PLN) at Thr17, which was identified as a CaMKII substrate in skeletal muscle, was rapidly (< 1 min) increased by exercise, and remained phosphorylated 5-fold above basal level during 90 min of exercise. The phosphorylation of serum response factor at Ser103, a putative CaMKII substrate, was higher after 30 min of exercise. PLN phosphorylation at Thr17 was higher with increasing exercise intensities. These data indicate that CaMKII is the major multifunctional CaMK in skeletal muscle and its activation occurs rapidly and is sustained during continuous exercise, with the activation being greater during intense exercise.
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Single skeletal muscle fiber behavior after a quick stretch in young and older men: a possible explanation of the relative preservation of eccentric force in old age.
Ochala, J, Dorer, DJ, Frontera, WR, Krivickas, LS
Pflugers Archiv : European journal of physiology. 2006;(4):464-70
Abstract
The origins of the smaller age-related decrease in eccentric force compared to isometric and concentric conditions in vivo remain unclear. Could this originate from contractile elements of muscle cells? The main intent of the current investigation was to assess the force behavior of muscle cells with aging, during lengthening. Chemically skinned single muscle fibers (n=235) from m. vastus lateralis of six young (mean age 31.6 years) and six older men (mean age 66.1 years) were maximally activated with pCa 4.5 at 15 degrees C. Maximal isometric force and cross-sectional area were measured allowing the calculation of the tension (T (0)). A quick stretch (2 nm per half-sarcomere length) was applied and caused an immediate increase in tension followed by a decrease and a secondary delayed and transient rise in tension (phase 3); finally, the tension recovered a steady state value (phase 4). The tension enhancements during phase 3 (DeltaT (3)) and phase 4 (DeltaT (4)) were evaluated. The myosin heavy-chain isoform composition of each single fiber was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. DeltaT (3) and DeltaT (4) were preserved in older men for both type I and IIa fibers despite a reduction in T (0). Therefore, the age-related preservation of the tension increments after a quick stretch in single muscle fibers could explain in part the smaller decrease in force during eccentric contractions compared to isometric and concentric conditions in vivo with aging usually observed.
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Repeated maximal eccentric actions causes long-lasting disturbances in movement control.
Bottas, R, Linnamo, V, Nicol, C, Komi, PV
European journal of applied physiology. 2005;(1-2):62-9
Abstract
This study examined acute and long-lasting effects of fatigue and muscle damage on fast and accurate elbow flexion and extension target movements (TM) with eight male students. An isokinetic machine was used to perform 100 maximal eccentric and concentric elbow flexions at 4-week intervals. Movement range was 40-170 degrees in eccentric exercise (ECCE) and 170-40 degrees in concentric exercise (CONE), with an angular velocity of 2 rad s(-1). TM was performed in sitting position with the right forearm fixed to lever arm above protractor. Subjects performed TM in horizontal plane (amplitude 60 degrees ) by visual feedback of movement from a television monitor. Surface EMG was recorded from the biceps brachii and triceps brachii muscles. TM measurements and serum creatine kinase (CK) determinations were conducted before, after, 0.5 h, 2 days, and 7 days after both exercises. Blood lactate was taken before, after, and 0.5 h after the exercises. Both ECCE and CONE led to a large decline in maximal voluntary contractions, but the recovery was slower after ECCE when it remained incomplete even until day 7 post-exercise. Lactate increased (P < 0.001) similarly after both exercises. Delayed-onset muscle soreness peaked on day 2 and CK peaked on day 7 after ECCE. Exhaustive eccentric exercise of agonistic muscles impaired the flexion TM performance, and had a long-duration modulation effect on the triphasic EMG activity pattern of flexion and extension TM. In the acute phase, the observed changes in performance and in the EMG patterns are suggested to be related to metabolic changes via III and IV muscle afferents. The delayed recovery, on the other hand, may be related to problems in the proprioceptive feedback caused by muscle damage.
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Influence of muscle glycogen availability on ERK1/2 and Akt signaling after resistance exercise in human skeletal muscle.
Creer, A, Gallagher, P, Slivka, D, Jemiolo, B, Fink, W, Trappe, S
Journal of applied physiology (Bethesda, Md. : 1985). 2005;(3):950-6
Abstract
Two pathways that have been implicated for cellular growth and development in response to muscle contraction are the extracellular signal-regulated kinase (ERK1/2) and Akt signaling pathways. Although these pathways are readily stimulated after exercise, little is known about how nutritional status may affect stimulation of these pathways in response to resistance exercise in human skeletal muscle. To investigate this, experienced cyclists performed 30 repetitions of knee extension exercise at 70% of one repetition maximum after a low (2%) or high (77%) carbohydrate (LCHO or HCHO) diet, which resulted in low or high (approximately 174 or approximately 591 mmol/kg dry wt) preexercise muscle glycogen content. Muscle biopsies were taken from the vastus lateralis before, approximately 20 s after, and 10 min after exercise. ERK1/2 and p90 ribosomal S6 kinase phosphorylation increased (P < or = 0.05) 10 min after exercise, regardless of muscle glycogen availability. Akt phosphorylation was elevated (P < 0.05) 10 min after exercise in the HCHO trial but was unaffected after exercise in the LCHO trial. Mammalian target of rapamycin phosphorylation was similar to that of Akt during each trial; however, change or lack of change was not significant. In conclusion, the ERK1/2 pathway appears to be unaffected by muscle glycogen content. However, muscle glycogen availability appears to contribute to regulation of the Akt pathway, which may influence cellular growth and adaptation in response to resistance exercise in a low-glycogen state.
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Functional roles of lower-limb joint moments while walking in water.
Miyoshi, T, Shirota, T, Yamamoto, S, Nakazawa, K, Akai, M
Clinical biomechanics (Bristol, Avon). 2005;(2):194-201
Abstract
OBJECTIVE To clarify the functional roles of lower-limb joint moments and their contribution to support and propulsion tasks while walking in water compared with that on land. DESIGN Sixteen healthy, young subjects walked on land and in water at several different speeds with and without additional loads. BACKGROUND Walking in water is a major rehabilitation therapy for patients with orthopedic disorders. However, the functional role of lower-limb joint moments while walking in water is still unclear. METHODS Kinematics, electromyographic activities in biceps femoris and gluteus maximums, and ground reaction forces were measured under the following conditions: walking on land and in water at a self-determined pace, slow walking on land, and fast walking in water with or without additional loads (8 kg). The hip, knee, and ankle joint moments were calculated by inverse dynamics. RESULTS The contribution of the walking speed increased the hip extension moment, and the additional weight increased the ankle plantar flexion and knee extension moment. CONCLUSIONS The major functional role was different in each lower-limb joint muscle. That of the muscle group in the ankle is to support the body against gravity, and that of the muscle group involved in hip extension is to contribute to propulsion. In addition, walking in water not only reduced the joint moments but also completely changed the inter-joint coordination. RELEVANCE It is of value for clinicians to be aware that the greater the viscosity of water produces a greater load on the hip joint when fast walking in water.