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Physiological responses at various lactate markers for running at 4 and 8 minute treadmill increments: Physiological responses at various lactate markers
No full textWe compared physiological responses corresponding to speeds at plasma lactate markers between incremental treadmill running of 4 and 8 min stages in fifteen healthy men (23 ± 4 yrs, 1.78 ± 0.49 m, 72.7 ± 10.8 kg).
Treadmill speed, oxygen uptake (VO2), heart rate (HR), rating of perceived exertion (RPE) and plasma lactate were measured for each stage, and calculated at: fixed blood lactate accumulation (FBLA) 4.0 mmol/L, an initial 1 mmol/L rise, deviation maximum (D max), lactate threshold (LT) and log-log LT.
There was no effect (p>0.05) of stage duration on speed, VO2, HR and RPE at fixed markers. For 8 min stages, speed was lower at modelled markers: D max (-1.1 km/h; p=0.001), LT (-0.9 km/h; p=0.008) and log-log LT (-0.8 km/h; p=0.006), yet RPE was higher and VO2 lower for LT (1.1, p= 0.02; -0.27 L/min, p=0.01) and log-log LT (1.4, p=0.03; -0.29 L/min, p=0.002). Lactate and VO2 were greater at 8 km/h for 4 min (p=0.0001), then similar until 11 km/h, with a trend towards elevated plasma lactate for 4 min thereafter.
When applying lactate threshold markers to assess physiological responses to incremental running, protocols using prolonged stage durations may underestimate marker running speed
Reproducibility of lactate markers during 4 and 8 min stage incremental running: A pilot study
Get PDFOBJECTIVES:
This study examined the reproducibility of speed corresponding to specific lactate markers during incremental treadmill running of normal and prolonged stage durations.
DESIGN:
Nineteen healthy participants (14 male, 5 female) performed repeated, incremental treadmill running trials of 4 and 8 min stages on separate days to examine the test-retest reproducibility of speed at lactate markers. Two trials were completed for each duration in a randomised order.
METHODS:
Fingertip blood samples drawn upon stage completion were analysed for plasma lactate, then used to determine running speed at: 2.0, 3.5, and 4.0 mmol l(-1) fixed blood lactate accumulations (FBLA), a 1 mmol l(-1) rise from baseline, and the markers: the deviation maximum (Dmax), the Dmax of the second curve derivative (D2L(max)), the lactate threshold (LT) and log-log LT.
RESULTS:
The 2.0 mmol l(-1) FBLA reported the lowest mean bias between 4 min trials (-0.06 km h(-1)), with the narrowest limits of agreement (LoA) (-1.78 to 1.66 km h(-1)). The Dmax had the second lowest bias (0.14 km h(-1)), D2L(max) the second narrowest LoA (-1.93 to 2.90 km h(-1)). For 8 min stages, the 1 mmol l(-1) rise demonstrated, low mean bias (-0.13 km h(-1)) and narrowest LoA (-1.22 to 0.97 km h(-1)) between trials.
CONCLUSIONS:
This preliminary report suggests the reproducibility of running speed at lactate summary markers is influenced by stage duration for incremental treadmill running. Varied marker reproducibility between 4 and 8 min stages indicates different blood lactate response, and therefore workload calculation, according to stage length. Consideration of marker construct is recommended
Effect of eccentric exercise with reduced muscle glycogen on plasma interleukin-6 and neuromuscular responses of m. quadriceps femoris.
Get PDFEccentric exercise can result in muscle damage and interleukin-6 (IL-6) secretion. Glycogen availability is a potent stimulator of IL-6 secretion. We examined effects of eccentric exercise in a low glycogen state on neuromuscular function and plasma IL-6 secretion. Twelve active males (23 ± 4 years, 179 ± 5 cm, 77 ± 10 kg) completed two downhill treadmill runs (gradient, -12%, 5x8 min; speed, 12.1 ± 1.1 km∙h-1) with normal (NG) and reduced muscle glycogen (RG) in randomized order and at least six weeks apart. Muscle glycogen was reduced using an established cycling protocol until exhaustion and dietary manipulation the evening before the morning run. Physiological responses were measured up to 48 h after the downhill runs. During recovery, force deficits of m. quadriceps femoris by maximal isometric contractions were similar. Changes in low-frequency fatigue were larger with RG. Voluntary activation and plasma IL-6 levels were similar in recovery between conditions. It is concluded that unaccustomed, damaging eccentric exercise with low muscle glycogen of the m. quadriceps femoris: i) exacerbated low-frequency fatigue, but ii) had no additional effect on IL-6 secretion. Neuromuscular impairment after eccentric exercise with low muscle glycogen appears to have a greater peripheral component in early recovery
The effect of glycogen reduction on cardiorespiratory and metabolic responses during downhill running
Get PDFPurpose Exercise-induced muscle damage and lowered glycogen are common during heavy training periods, and may prolong recovery. We examined the effects of lowered glycogen on cardiorespiratory, metabolic and perceptual responses to downhill running. Methods Twelve men performed two downhill runs (−12 % gradient, 12.1 ± 1.1 km/h) separated by 6 weeks, under normal (NORM) and reduced glycogen (RED) conditions in a crossover design. For RED, participants performed exhaustive cycling at 60 % VO2max power (95 ± 13 min) in the evening, and the next morning completed a downhill run comprising of five stages of 8 min running, with 2 min recovery (1 % gradient, 8 km/h) between each stage. Expired gas, heart rate, rating of perceived exertion (RPE) and blood lactate (bLa) and glucose were measured for each stage. Results Blood glucose (P < 0.05) and respiratory exchange ratio (P < 0.01) were lower in RED, than NORM, throughout the downhill run. RED demonstrated higher bLa until stage Four (P < 0.05), and RPE for stages Two and Five (P < 0.05). Ventilatory equivalent of carbon dioxide output (VE/VCO2) was higher for stages One (P < 0.01), Two and Five (P < 0.05), and oxygen uptake (VE/VO2) was lower for stages Three and Four (P < 0.05) for RED. Conclusions Downhill running with reduced glycogen, elevated fat oxidation and bLa response, and, in part, increased effort perception. The alterations in VE/VO2 and bLa may suggest that carbon dioxide removal was somewhat impaired
Neuromuscular responses to mild-muscle damaging eccentric exercise in a low glycogen state.
Get PDFThe aim of this study was to examine the effect of low muscle glycogen on the neuromuscular responses to maximal eccentric contractions. Fourteen healthy men (22±3years) performed single-leg cycling (20min at ∼75% maximal oxygen uptake (V̇O2 max); eight 90 s sprints at a 1:1 work-to-rest ratio (5% decrements from 90% to 55% V̇O2 max until exhaustion) the evening before 100 eccentric (1.57rads(-1)) with reduced (RED) and normal glycogen (NORM). Neuromuscular responses were measured during and up to 48h after with maximal voluntary and involuntary (twitch, 20Hz and 50Hz) isometric contractions. During eccentric contractions, peak torque decreased (RED: -16.1±2.5%; NORM: -6.2±5.1%) and EMG frequency increased according to muscle length. EMG activity decreased for RED only. After eccentric contractions, maximal isometric force was reduced up to 24h for NORM (-13.5±5.8%) and 48h for RED (-7.4±10.9%). Twelve hours after eccentric contractions, twitch force and the 20:50Hz ratio were decreased for RED but not for NORM. Immediate involuntary with prolonged voluntary force loss suggests that reduced glycogen is associated with increased susceptibility to mild muscle-damaging eccentric exercise with contributions of peripheral and central mechanisms to be different during recovery
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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