1,721,239 research outputs found
The effects of training intensity on muscle buffer capacity in females
No full textWe examined changes in muscle buffer capacity (beta m(in vitro)), VO2peak and the lactate threshold (LT) after 5 weeks of high-intensity interval training (INT) above the LT or moderate-intensity continuous training (CON) just below the LT. Prior to and immediately after training, 16 female subjects performed a graded exercise test to determine VO2peak and the LT, followed 2 days later by a resting muscle biopsy from the vastus lateralis muscle to determine beta m(in vitro). Following baseline testing, the subjects were randomly placed into the INT (n=8) or CON training group (n=8). Subjects then performed 5 weeks of cycle training (3 days per week), performing either high-intensity INT (6-10x2 min at 120-140\% LT with 1 min rest) or moderate-intensity CON (80-95\% LT) training. Total training volume was matched between the two groups. After the training period, both groups had significant improvements in VO2peak (12-14\%; P0.05). Our results show that when matched for training volume, high-intensity interval training above the LT results in similar improvements in VO2peak and the LT, but greater improvements in beta m(in vitro) than moderate-intensity continuous training below the LT. This suggests that training intensity is an important determinant of changes to beta m(in vitro)
Effects of high-intensity interval training on the VO2 response during severe exercise
No full textThis study examined the effect of high-intensity interval training on the VO2 response during severe, constant-load exercise. Prior to, and following training, 10 females (V O2 peak 37.4+/-6.0 mL kg-1 min-1) performed a graded exercise test to determine VO2 peak and lactate threshold (LT) and a 6 min cycle test (CT) at the pre-training VO2 peak intensity. Training involved high-intensity intervals (2 min work, 1 min rest) performed 3x week for 8 weeks. Breath-by-breath data from 0 to 6 min during the CT were smoothed using 5s averages and fit to a bi-exponential model starting from 20s. Training resulted in significant improvements in VO2 max (2.34+/-0.37-2.78+/-0.30 L min-1), power at VO2 max (170+/-26-204+/-25 W) and power at LT (113+/-17-136+/-20 W) (p0.05) in the time constants of either phase or the amplitude of the slow component (318+/-67-380+/-48 mL; p=0.15). In conjunction, accumulated oxygen deficit (AOD) (43.7+/-9.8-17.2+/-2.8 mL O2 eq kg-1) and anaerobic contribution to the CT (19.4+/-4.4-7.2+/-1.2\%) were significantly reduced. In contrast to previous moderate-intensity research, a high-intensity interval training program increased A1 and VO2 EE for the same absolute exercise intensity, decreasing the AOD during a severe-intensity CT
Effects of chronic NaHCO3 ingestion during interval training on changes to muscle buffer capacity, metabolism, and short-term endurance performance
No full textThis study determined the effects of altering the H(+) concentration during interval training, by ingesting NaHCO(3) (Alk-T) or a placebo (Pla-T), on changes in muscle buffer capacity (beta m), endurance performance, and muscle metabolites. Pre- and posttraining peak O(2) uptake (V(O2 peak)), lactate threshold (LT), and time to fatigue at 100\% pretraining V(O2 peak) intensity were assessed in 16 recreationally active women. Subjects were matched on the LT, were randomly placed into the Alk-T (n = 8) or Pla-T (n = 8) groups, and performed 8 wk (3 days/wk) of six to twelve 2-min cycle intervals at 140-170\% of their LT, ingesting NaHCO(3) or a placebo before each training session (work matched between groups). Both groups had improvements in beta m (19 vs. 9\%; P < 0.05) and V(O2 peak) (22 vs. 17\%; P < 0.05) after the training period, with no differences between groups. There was a significant correlation between pretraining beta m and percent change in beta m (r = -0.70, P < 0.05). There were greater improvements in both the LT (26 vs. 15\%; P = 0.05) and time to fatigue (164 vs. 123\%; P = 0.05) after Alk-T, compared with Pla-T. There were no changes to pre- or postexercise ATP, phosphocreatine, creatine, and intracellular lactate concentrations, or pH(i) after training. Our findings suggest that training intensity, rather than the accumulation of H(+) during training, may be more important to improvements in beta m. The group ingesting NaHCO(3) before each training session had larger improvements in the LT and endurance performance, possibly because of a reduced metabolic acidosis during training and a greater improvement in muscle oxidative capacity
Muscle buffer capacity and aerobic fitness are associated with repeated-sprint ability in women
No full textIn addition to a high aerobic fitness, the ability to buffer hydrogen ions (H+) may also be important for repeated-sprint ability (RSA). We therefore investigated the relationship between muscle buffer capacity (betamin vivo and betamin vitro) and RSA. Thirty-four untrained females [mean (SD): age 19 (1) years, maximum oxygen uptake (VO2peak) 42.3 (7.1) ml x kg(-1) x min(-1)] completed a graded exercise test (GXT), followed by a RSA cycle test (five 6-s sprints, every 30 s). Capillary blood was sampled during the GXT and before and after the RSA test to determine blood pH (pHb) and lactate concentration ([La-]b). Muscle biopsies were taken before (n=34) and after (n=23) the RSA test to determine muscle lactate concentration ([La-]i), hydrogen ion concentration ([H+]i) pHi, betamin vivo and betamin vitro. There were significant correlations between work decrement (\%) and betamin vivo (r=-0.72, P<0.05), VO2peak (r=-0.62, P<0.05), lactate threshold (LT) (r=-0.56, P<0.05) and changes in [H+]i (r=0.41, P<0.05). There were however, no significant correlations between work decrement and betamin vitro, or changes in [La-]i, or [La-]b. There were also no significant correlations between total work (J x kg(-1)) during the RSA test and betamin vitro, betamin vivo, or changes in [La-]i, pHi, [La-]b, or pHb. There were significant correlations between total work (J x kg(-1)) and both VO2peak (r=0.60, P<0.05) and LT(r=0.54, P<0.05). These results support previous research, identifying a relationship between RSA and aerobic fitness. This study is the first to identify a relationship between betamin vivo and RSA. This suggests that the ability to buffer H+ may be important for maintaining performance during brief, repeated sprints
Determinants of repeated-sprint ability in females matched for single-sprint performance
No full textThis study investigated the relationship between VO2max and repeated-sprint ability (RSA), while controlling for the effects of initial sprint performance on sprint decrement. This was achieved via two methods: (1) matching females of low and moderate aerobic fitness (VO2max: 36.4 ± 4.7 vs 49.6 ± 5.5 ml kg−1 min−1 ; p 0.05) to r = −0.50 (p < 0.05). These results indicate that VO2max does contribute to performance during repeated-sprint efforts. However, the small variance in W dec explained by VO2max suggests that other factors also play a role
The effects of a 10-day taper on repeated-sprint performance in females
No full textWhile taper is a well-established practice in most endurance sports, no study has investigated the effects of taper on repeated-sprint ability (RSA). Eleven female, recreational, team-sport athletes (mean±SD: age = 19±3 y, V̇O2max = 39.0±6.4 mL·kg−1·min−1) trained intensively three times per week for six weeks. Each week (on a non-training day), subjects performed a RSA test (5 × 6-s sprints every 30 s). Following the training period, subjects were given a 10-day exponential taper followed by a final RSA test. Following the taper, there was a non-significant increase in both total work (4.4% increase; P= 0.16) and peak power (3.2% increase; P= 0.18) during the 5 × 6-s test. There was however a significant decrease in work decrement (Wk 6: 10.2±3.5% v Wk 8: 7.9±4.3%; P< 0.05) following the 10-day taper. This is the first study to report the effects of taper on repeated-sprint performance. While not significant, the 10-day taper did result in a 3%–4% improvement in performance. Similar percentage improvements have been reported in swimmers and runners following seven to 14-day tapers. Further research is required to structure the optimal taper to improve repeated-sprint performance
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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