Neuromuscular responses to different resistance loading protocols using pneumatic and weight stack devices

The purpose of this study was to examine single repetition characteristics and acute neuromuscular responses to typical hypertrophic (HL), maximal strength (MSL), and power (PL) loadings performed with two of the most common resistance modes; pneumatic and weight stack. Acute responses were assessed by measuring maximal voluntary contraction (MVC), corresponding quadriceps-EMG and resting and superimposed twitch torques. Activation level was calculated from the twitch torques.Decreases in MVC were greater during HL and MSL than during PL. During HL, resting twitch force decreased 8% (P < 0.05) more on the weight stack than on the pneumatic device. Furthermore, loading using the weight stack caused reduced resting twitch force, activation level, and EMG-amplitude after MSL and PL (P < 0.05–0.01).PL on the pneumatic device decreased MVC and rapid force production, while the respective PL on the weight stack device was specific to decreased rapid force production only. However, mean angular velocities and power of the repetitions were higher on the pneumatic device when using light loads.The present study showed that, at least in untrained subjects, the weight stack device induced greater levels of peripheral fatigue during HL. It also led to large central fatigue during MSL and PL. On the other hand, on the pneumatic device contraction velocity with low loads was higher compared to the weight stack device.Therefore, it is recommended that the resistance mode should be chosen according to the specific training goal.     

Influence of exercise order in a resistance-training exercise session

The order of resistance exercises within a training session may have a vital impact on the quality of the constituent exercises performed. However, very few studies have documented the specific influence of exercise order. Therefore, the purpose of this study was to examine the effect of exercise order on back squat performance in the context of a whole-body workout. Nine resistance-trained male subjects (age: 24 +/- 4 years, body mass: 81.5 +/- 15.3 kg, resistance-training experience: 7 +/- 4 years) performed the back squat exercise (4 sets at 85% of 1 repetition maximum) on 2 separate occasions in a balanced, crossover design. During one protocol, the squat exercise was performed first (protocol A); during the other protocol, it was performed after a whole-body resistance-exercise session (protocol B). Number of repetitions, average power, and rating of perceived exertion (RPE) were collected during each set of the squat exercise. All subjects performed significantly (p < 0.01) more repetitions during set 1 when they performed protocol A (8.0 +/- 1.9 repetitions) compared with protocol B (5.4 +/- 2.7 repetitions). The average power for each set was higher during protocol B compared with protocol A. There were no significant differences in RPE values between the 2 protocols. In conclusion, performing the barbell back squat first in an exercise session allowed the completion of more total repetitions. However, this study showed that performing the squat exercise after a whole-body workout session may result in greater power output if the squat is preceded by a power exercise (i.e., hang pull). This phenomenon may have been due to postactivation potentiation.     

Utility of plasma apelin and other indices of cardiac dysfunction in the clinical assessment of patients with dilated cardiomyopathy

Apelin is a recently discovered peptide ligand reported to be involved in the regulation of cardiovascular homeostasis. The exact role of apelin in the pathophysiology of congestive heart failure has remained obscure, and the reported circulating levels of apelin in patients with heart failure have been contradictory. To establish the role of apelin in the assessment of cardiac dysfunction we measured plasma apelin levels in 65 patients with congestive heart failure caused by idiopathic dilated cardiomyopathy (IDC) and 14 healthy volunteers by specific radioimmunoassay. IDC patients were carefully examined including echocardiography, both-sided cardiac catheterization and cardiopulmonary exercise test. In addition, plasma levels of N-terminal pro-brain natriuretic peptide (NT-proBNP), N-terminal pro-atrial natriuretic peptide (NT-proANP), interleukin (IL)-6, tumor necrosis factor alpha (TNF-), epinephrine and norepinephrine were determined. Plasma apelin levels were similar in IDC patients (median 26.5 pg/ml, range < 3.40–97.6 pg/ml) and in control subjects (median 24.1 pg/ml, range 19.0–28.7 pg/ml; p = NS). Unlike the levels of NT-proBNP, IL-6, TNF-, and norepinephrine, plasma apelin levels did not reflect the severity of heart failure. Our study demonstrates that although disturbed apelin–APJ signalling in heart may play a role in the pathophysiology of heart failure, circulating apelin levels cannot be applied in the clinical assessment of patients with chronic left ventricular dysfunction.     

Phylogenetic analysis of the SAP30 family of transcriptional regulators reveals functional divergence in the domain that binds the nuclear matrix

Background  

Deacetylation of histones plays a fundamental role in gene silencing, and this is mediated by a corepressor complex containing Sin3 as an essential scaffold protein. In this report we examine the evolution of two proteins in this complex, the Sin3-associated proteins SAP30L and SAP30, by using an archive of protein sequences from 62 species.     

Strength and power profiles of the lower and upper extremities in master throwers at different ages

Thirty-two master athletes (shot put, discus, and hammer throw) were divided into 4 groups according to their age (T40 [40 years of age], 50 [50 years of age], 60 [60 years of age], and 75 [75 years of age]). Twenty-eight age-matched men served as controls (C40 [40 years of age], 50 [50 years of age], 60 [60 years of age], and 75 [75 years of age]). The subjects were tested for maximal isometric strength of the lower and upper extremities. Power was measured by performing jump squats and bench press in the Smith machine with the load of 60% of 1 repetition maximum. Electromyographic (EMG) activity was recorded from 6 different muscles. The muscle thickness of vastus lateralis and intermedius (VL+VI) and triceps brachii (TB) was measured by ultrasound. Maximal strength differed (p < 0.05- 0.001) in all testing actions between T40 and T60 and T40 and T75 as well as between T and C groups. Both VL+VI and TB thickness in T40 was greater (p < 0.05-0.01) than in T60 and T75 and in T was larger than in C groups. Average force during the first 500 milliseconds (ms) was higher (p < 0.05-0.001) in T40 compared to T50, T60, and T75 in bilateral leg extension, biceps curl, and especially in unilateral knee flexion. T40 produced higher power than the other groups (p < 0.05-0.001). The relative agonist EMG activation (VL) in leg extension during the first 100 ms compared to maximum activation was lower (p < 0.05) in T50, T60, and T75, but not in T40. The present data indicate that maximal strength and muscle thickness as well as explosive strength and power characteristics decline with aging also in master athletes who carry out strength training and throwing exercises actively over several decades. Nevertheless, in master athletes, maximal strength and muscle mass as well as explosive force production of the upper and lower extremities seem to be at remarkably higher levels than those recorded for age-matched control men.     

Easy and Rapid Detection of Mumps Virus by Live Fluorescent Visualization of Virus-Infected Cells

Mumps viruses show diverse cytopathic effects (CPEs) of infected cells and viral plaque formation (no CPE or no plaque formation in some cases) depending on the viral strain, highlighting the difficulty in mumps laboratory studies. In our previous study, a new sialidase substrate, 2-(benzothiazol-2-yl)-4-bromophenyl 5-acetamido-3,5-dideoxy-α-D-glycero-D-galacto-2-nonulopyranosidonic acid (BTP3-Neu5Ac), was developed for visualization of sialidase activity. BTP3-Neu5Ac can easily and rapidly perform histochemical fluorescent visualization of influenza viruses and virus-infected cells without an antiviral antibody and cell fixation. In the present study, the potential utility of BTP3-Neu5Ac for rapid detection of mumps virus was demonstrated. BTP3-Neu5Ac could visualize dot-blotted mumps virus, virus-infected cells, and plaques (plaques should be called focuses due to staining of infected cells in this study), even if a CPE was not observed. Furthermore, virus cultivation was possible by direct pick-up from a fluorescent focus. In conventional methods, visible appearance of the CPE and focuses often requires more than 6 days after infection, but the new method with BTP3-Neu5Ac clearly visualized infected cells after 2 days and focuses after 4 days. The BTP3-Neu5Ac assay is a precise, easy, and rapid assay for confirmation and titration of mumps virus.     

Metabolic compartmentation of pyruvate in the isolated perfused rat heart.

1. Prompted by the finding of markedly differing specific radioactivities of tissue alanine and lactate in isolated rat hearts perfused with [1-14C]pyruvate, a more detailed study on the cytosolic subcompartmentalization of pyruvate was undertaken. Isolated rat hearts were perfused by the once-through Langendorff technique under metabolic and isotopic steady-state conditions but with various routes of radioactive label influx, and the specific radioactivities of pyruvate, lactate and alanine were determined. An enzymic method was devised to determine the specific radioactivity of C-1 of pyruvate. 2. Label introduction as [1-14C]pyruvate resulted in a higher specific radioactivity of tissue alanine and mitochondrial pyruvate than of lactate, and a higher specific radioactivity of perfusate lactate than of tissue lactate. Label introduction as [1-14C]lactate resulted in a roughly similar isotope dilution into the tissue and perfusate pyruvate and the tissue alanine. Label introduction as [3,4-14C]glucose resulted in the same specific radioactivity of tissue lactate and alanine and a roughly similar specific radioactivity of mitochondrial pyruvate. 3. The results can be reconciled with a metabolic model containing two cytosolic functional pyruvate pools. One pool (I) communicates more closely with the glycolytic system, whereas the other (II) communicates with extracellular pyruvate and intracellular alanine. Pool II is in close connection with intramitochondrial pyruvate. The physical identity of the cytosolic subcompartments of pyruvate is discussed.     

Effect of resistance exercise on muscle steroid receptor protein content in strength-trained men and women

The purpose of this study was to examine the acute effect of resistance exercise (RE) on muscle androgen receptor (AR) and glucocorticoid receptor (GR) protein content. Fifteen resistance-trained men (n = 8; 21 ± 1 years, 175.3 ± 6.7 cm, 90.8 ± 11.6 kg) and women (n = 7; 24 ± 5 years, 164.6 ± 6.7 cm, 76.4 ± 15.6 kg) completed 6 sets of 10 repetitions of heavy squats. Blood samples were obtained before RE, after 3 and 6 sets of squats, and 5, 15, 30 and 70 min after RE. Muscle biopsies from the vastus lateralis were obtained before RE, and 10 min and 70 min after RE. Blood samples were analyzed for total and free testosterone concentrations and muscle samples were analyzed for AR and GR protein content. Circulating total testosterone increased significantly (p ≤ 0.05) in men and free testosterone increased in men and women with exercise. AR was significantly reduced at 70 min post-exercise in men and at 10 min post-exercise in women compared to pre-exercise. There were no changes in GR following RE, but GR was significantly higher in women compared to men. These findings support a current paradigm for stabilization followed by a reduction and then a rebound in the acute AR response to RE but demonstrate that gender differences exist in the timeline of the AR response.     

Neuromuscular performance characteristics of open-wheel and rally drivers

The purpose of the present study was to investigate neuromuscular performance characteristics in open-wheel and rally drivers using the cross-sectional study design. The subjects (N = 28) consisted of experienced international-level open-wheel drivers (n = 9), experienced international-level rally drivers (n = 9) and a physically active nondriving male control group (n = 10). In 3 separate test sessions, speed, muscle strength, and endurance tests were performed. The rally drivers had higher (p < 0.05) grip, shoulder flexion, and ankle plantar flexion strength, as compared to the control group. The open-wheel drivers showed higher strengths (p < 0.05) than the controls in neck forces, grip, shoulder flexion, and leg extension. The rally drivers were stronger (p < 0.05) than the open-wheel drivers in grip, plantar flexion, and trunk extension forces, whereas the open-wheel drivers were stronger (p < 0.01) than the rally drivers in neck lateral flexions and extension forces. Thus, competitive long-term open-wheel and rally drivers differ specifically in neuromuscular performance. For practice, these findings suggest that rally drivers should concentrate on training hand, ankle, and trunk muscles, whereas open-wheel drivers should train neck muscles, especially, and all other muscle groups rather equally.