320 research outputs found
Purinergic effects on Na,K-ATPase activity differ in rat and human skeletal muscle
activity of the Na,K-ATPase in rat muscle. The hypothesis that a similar mechanism is present in human skeletal muscle was investigated with membranes from rat and human skeletal muscle. dependent Na,K-ATPase activity in rat muscle membranes, whereas similar treatments of human muscle membranes lowered the Na,K-ATPase activity. UTP incubation resulted in unchanged Na,K-ATPase activity in humans, but pre-incubation with the antagonist suramin resulted in inhibition with UTP, suggesting that P2Y receptors are involved. The Na,K-ATPase in membranes from both rat and human could be stimulated by protein kinase A and C activation. Thus, protein kinase A and C activation can increase Na,K-ATPase activity in human muscle but not via P2Y receptor stimulation. receptor).Rat muscle is not a reliable model for purinergic effects on Na,K-ATPase in human skeletal muscle
Front crawl swimming analysis using accelerometers:A preliminary comparison between pool and flume
AbstractBiomechanical characteristics such as stroke rate and stroke length can be used to determine the velocity of a swimmer and can be analysed in both a swimming pool and a flume. The aim of the present preliminary study was to investigate the differences between the acceleration data collected from a swimming pool with that collected from a flume, as a function of the swimmer's stroke rate and stroke count, with the objective of identifying the impact on the swimmer's performance. The differences were determined by the analysis of the stroke's features, comparing several strokes normalized to one stroke count from an elite swimmer. Triaxial accelerometer logging using a sensor located in an arm band positioned immediately in the wrist was used to record the swimmer's stroke. There is statistical evidence that show that there are small differences between the pool and flume on medio-lateral wrist movements (0.64 < r < 0.75). The correlation coefficients are (0.75 < r < 0.83) and (0.82 < r < 0.89) for the other two axes
Effects of 12 weeks high-intensity & reduced-volume training in elite athletes
It was investigated if high-intensity interval training (HIT) at the expense of total training volume improves performance, maximal oxygen uptake and swimming economy. 41 elite swimmers were randomly allocated to a control (CON) or HIT group. For 12 weeks both groups trained âŒ12 h per week. HIT comprised âŒ5 h vs. 1 h and total distance was âŒ17 km vs. 35 km per week for HIT and CON, respectively. HIT was performed as 6-10Ă10-30 s maximal effort interspersed by 2â4 minutes of rest. Performance of 100 m all-out freestyle and 200 m freestyle was similar before and after the intervention in both HIT (60.4±4.0 vs. 60.3±4.0 s; nâ=â13 and 133.2±6.4 vs. 132.6±7.7 s; nâ=â14) and CON (60.2±3.7 vs. 60.6±3.8 s; nâ=â15 and 133.5±7.0 vs. 133.3±7.6 s; nâ=â15). Maximal oxygen uptake during swimming was similar before and after the intervention in both the HIT (4.0±0.9 vs. 3.8±1.0 l O(2)Ămin(â1); nâ=â14) and CON (3.8±0.7 vs. 3.8±0.7 l O(2)Ămin(â1); nâ=â11) group. Oxygen uptake determined at fixed submaximal speed was not significantly affected in either group by the intervention. Body fat % tended to increase (Pâ=â0.09) in the HIT group (15.4±1.6% vs. 16.3±1.6%; Pâ=â0.09; nâ=â16) and increased (P<0.05) in the CON group (13.9±1.5% vs. 14.9±1.5%; nâ=â17). A distance reduction of 50% and a more than doubled HIT amount for 12 weeks did neither improve nor compromise performance or physiological capacity in elite swimmers
Does intermittent exposure to high altitude increase the risk of cardiovascular disease in workers? A systematic narrative review
Objective Several working groups (eg, miners, flight
crews and soldiers) are subjected to chronic intermittent
hypoxic exposure. The cardiovascular implications have
been studied but not systematically reviewed with focus
on possible negative health implications. The aim of
the present review was to systematically evaluate the
hypothesis that intermittent hypoxic exposure causes
cardiovascular stress detrimental to health in workers.
Design Systematic review.
Data sources Electronic database search of PubMed,
Scopus and Web of Science up to April 2020.
Eligibility criteria Studies of workers â„18 years
repeatedly subjected to months to years of irregular
intermittent hypoxia, lasting from a few hours (eg, flight
crews), one or a few days (eg, soldiers), or several days
to weeks (eg, miners working at high altitude), written in
English and evaluating the effect of intermittent hypoxia
on cardiovascular disease were included. Animal studies,
books, book chapters, personal communication and
abstracts were excluded. The primary outcome measure
was changes in standardised mortality ratio.
Data extraction and synthesis Two independent
reviewers extracted data and assessed risk of bias using
the Cochrane Collaborationâs tool.
Results 119 articles were identified initially, 31 of which
met the inclusion criteria. Of these, 17 were retrospective
cohort mortality studies (irregular short-term
intermittent
hypoxia), and 14 studies were observational (long-term
intermittent hypoxia). The population of irregular
short-term
intermittent hypoxia users (flight crew)
showed a lower mortality by cardiovascular disease.
Long-term
intermittent hypoxia over several years
such as in miners or soldiers may produce increased
levels of cardiac disorders (12 studies), though this is
probably confounded by factors such as obesity and
socioeconomic status.
Conclusion This systematic narrative review found that
cardiovascular disease mortality in flight crews is lower
than average, whereas miners and soldiers exposed
to intermittent hypoxia experience increased risks of
cardiovascular diseases. The impact of socioeconomic
status and lifestyle appears of importance.FundaciĂłn Alfonso Martin Escudero' (Spain
Fast-Twitch Glycolytic Skeletal Muscle Is Predisposed to Age-Induced Impairments in Mitochondrial Function
The etiology of mammalian senescence is suggested to involve the progressive impairment of mitochondrial function; however, direct observations of age-induced alterations in actual respiratory chain function are lacking. Accordingly, we assessed mitochondrial function via high-resolution respirometry and mitochondrial protein expression in soleus, quadricep, and lateral gastrocnemius skeletal muscles, which represent type 1 slow-twitch oxidative muscle (soleus) and type 2 fast-twitch glycolytic muscle (quadricep and gastrocnemius), respectively, in young (10-12 weeks) and mature (74-76 weeks) mice. Electron transport through mitochondrial complexes I and III increases with age in quadricep and gastrocnemius, which is not observed in soleus. Mitochondrial coupling efficiency during respiration through complex I also deteriorates with age in gastrocnemius and shows a tendency (p = .085) to worsen in quadricep. These data demonstrate actual alterations in electron transport function that occurs with age and are dependent on skeletal muscle typ
High-intensity intermittent swimming improves cardiovascular health status for women with mild hypertension
To test the hypothesis that high-intensity swim training improves cardiovascular health status in sedentary premenopausal women with mild hypertension, sixty-two women were randomized into high-intensity (n=21; HIT), moderate-intensity (n=21; MOD), and control groups (n=20; CON). HIT performed 6â10 Ă 30âs all-out swimming interspersed by 2 min recovery and MOD swam continuously for 1âh at moderate intensity for a 15-week period completing in total 44±1 and 43±1 sessions, respectively. In CON, all measured variables were similar before and after the intervention period. Systolic BP decreased (P<0.05) by 6±1 and 4±1âmmHg in HIT and MOD; respectively. Resting heart rate declined (P<0.05) by 5±1 bpm both in HIT and MOD, fat mass decreased (P<0.05) by 1.1±0.2 and 2.2±0.3âkg, respectively, while the blood lipid profile was unaltered. In HIT and MOD, performance improved (P<0.05) for a maximal 10âmin swim (13±3% and 22±3%), interval swimming (23±3% and 8±3%), and Yo-Yo IE1 running performance (58±5% and 45±4%). In conclusion, high-intensity intermittent swimming is an effective training strategy to improve cardiovascular health and physical performance in sedentary women with mild hypertension. Adaptations are similar with high- and moderate-intensity training, despite markedly less total time spent and distance covered in the high-intensity group
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