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1.
Appl Environ Microbiol ; 86(2)2020 01 07.
Artículo en Inglés | MEDLINE | ID: mdl-31676481

RESUMEN

Dietary fiber provides growth substrates for bacterial species that belong to the colonic microbiota of humans. The microbiota degrades and ferments substrates, producing characteristic short-chain fatty acid profiles. Dietary fiber contains plant cell wall-associated polysaccharides (hemicelluloses and pectins) that are chemically diverse in composition and structure. Thus, depending on plant sources, dietary fiber daily presents the microbiota with mixtures of plant polysaccharides of various types and complexity. We studied the extent and preferential order in which mixtures of plant polysaccharides (arabinoxylan, xyloglucan, ß-glucan, and pectin) were utilized by a coculture of five bacterial species (Bacteroides ovatus, Bifidobacterium longum subspecies longum, Megasphaera elsdenii, Ruminococcus gnavus, and Veillonella parvula). These species are members of the human gut microbiota and have the biochemical capacity, collectively, to degrade and ferment the polysaccharides and produce short-chain fatty acids (SCFAs). B. ovatus utilized glycans in the order ß-glucan, pectin, xyloglucan, and arabinoxylan, whereas B. longum subsp. longum utilization was in the order arabinoxylan, arabinan, pectin, and ß-glucan. Propionate, as a proportion of total SCFAs, was augmented when polysaccharide mixtures contained galactan, resulting in greater succinate production by B. ovatus and conversion of succinate to propionate by V. parvula Overall, we derived a synthetic ecological community that carries out SCFA production by the common pathways used by bacterial species for this purpose. Systems like this might be used to predict changes to the emergent properties of the gut ecosystem when diet is altered, with the aim of beneficially affecting human physiology.IMPORTANCE This study addresses the question as to how bacterial species, characteristic of the human gut microbiota, collectively utilize mixtures of plant polysaccharides such as are found in dietary fiber. Five bacterial species with the capacity to degrade polymers and/or produce acidic fermentation products detectable in human feces were used in the experiments. The bacteria showed preferential use of certain polysaccharides over others for growth, and this influenced their fermentation output qualitatively. These kinds of studies are essential in developing concepts of how the gut microbial community shares habitat resources, directly and indirectly, when presented with mixtures of polysaccharides that are found in human diets. The concepts are required in planning dietary interventions that might correct imbalances in the functioning of the human microbiota so as to support measures to reduce metabolic conditions such as obesity.


Asunto(s)
Bacterias/metabolismo , Microbioma Gastrointestinal , Técnicas de Cocultivo/métodos , Glucanos/metabolismo , Pectinas/metabolismo , Xilanos/metabolismo , beta-Glucanos/metabolismo
2.
J Sports Sci ; 38(22): 2517-2524, 2020 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-32648521

RESUMEN

Interrupting sedentary behaviour with regular activity breaks benefits glycaemic control; however, the influence of the energy utilised during these activity breaks on postprandial metabolic response is relatively unknown. Therefore, the aim of this study was to investigate whether the energy utilisation of regular (every 30 min) short (1 min 40 s or 2 min) activity breaks was associated with the lowering of postprandial glycaemia, insulinemia and lipidemia.Using separate data from two previously performed studies (ALPhA Study n = 65, age 25.7 (5.2) y, 40% male, BMI 23.6 (4.1) kg · m-2. ABPA study n = 35, age 25.1 (3.7) y, 31% male, BMI 23.4 (3.2) kg · m-2) we investigated the association between energy utilisation (measured by indirect calorimetry) and postprandial glucose, insulin and triglycerides during prolonged sitting, and regular activity breaks.Results.Mixed effects regression models indicated that energy utilisation was not consistently associated with postprandial glucose, insulin or triglyceride responses (p > 0.05 for all). Additionally, there was some indication that energy utilisation was obscuring (mildly suppressing) the effects of regular activity breaks on glucose, insulin and triglyceride iAUC.Conclusions.If energy utilisation does not mediate the association between regular activity breaks and postprandial glycaemic response, it is possible that it is the frequency of the activity breaks that is beneficial.


Asunto(s)
Metabolismo Energético , Ejercicio Físico/fisiología , Periodo Posprandial/fisiología , Conducta Sedentaria , Sedestación , Adolescente , Adulto , Área Bajo la Curva , Glucemia/metabolismo , Calorimetría Indirecta , Metabolismo de los Hidratos de Carbono , Femenino , Humanos , Insulina/sangre , Metabolismo de los Lípidos , Masculino , Oxidación-Reducción , Triglicéridos/sangre , Adulto Joven
3.
J Strength Cond Res ; 32(8): 2166-2173, 2018 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-28301443

RESUMEN

Salmon, DM, Handcock, PJ, Sullivan, SJ, Rehrer, NJ, and Niven, BE. Can neck strength be measured using a single maximal contraction in a simulated contact position? J Strength Cond Res 32(8): 2166-2173, 2018-Neck strengthening has been postulated to potentially reduce the incidence and severity of concussions and neck injuries in collision-based sports. A quick and reliable method to assess neck strength would permit identification of those at risk and tracking of progress after injury. The purpose of this study was to determine if neck strength could be reliably assessed in a simulated contact posture using a single maximal contraction. During a single session, 30 healthy male university students performed 3 maximal voluntary contractions of the neck musculature in each of the following directions: extension (Ext), flexion (Flx), left lateral flexion (LtFlx), and right lateral flexion (RtFlx). To evaluate the reliability of these measures, intraclass correlation coefficients (ICCs) were calculated. The findings revealed a significant effect for direction (p < 0.01), where Ext (234.8 N) tested stronger than Flx (141.0 N), LtFlx (134.5 N), and RtFlx (123.0 N). In addition, Flx tested stronger than RtFlx (p = 0.03). No other differences were observed between LtFlx and RtFlx. When the combined mean values of the trials (1: 151.6 N, 2: 160.0 N, 3: 163.5 N) and the interaction contrast were compared, these were not significant (p = 0.08-1.0), indicating no changes in peak force occurred over the 3 trials. The ICC values for Ext, RtFlx, and LtFlx were all "excellent" (0.91-0.94), whereas Flx demonstrated "good" reliability (0.86). In a simulated contact posture, a reliable measure of peak force was obtained using a single maximal contraction. This may have practical applications for the quick and reliable assessment of contact sport athletes in a position that has functional relevance to their sports.


Asunto(s)
Prueba de Esfuerzo/normas , Contracción Isométrica/fisiología , Fuerza Muscular/fisiología , Músculos del Cuello/fisiología , Adolescente , Humanos , Masculino , Rango del Movimiento Articular , Reproducibilidad de los Resultados , Adulto Joven
4.
J Strength Cond Res ; 29(3): 637-46, 2015 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-25226308

RESUMEN

The purpose of this study was to examine the reliability of repeated isometric measurements of neck strength and endurance in a simulated rugby contact posture. Data were collected from healthy active university students (n = 20) over 3 sessions. Each session consisted of a single maximal voluntary contraction (MVC) and endurance trial for extension and flexion. The endurance trials were analyzed to determine the area under the force curve (%AUC) and the time to fatigue (TTF). Reliability was calculated using the SEM and minimal detectable change (MDC). The results revealed that the MVC values for extension were nonsignificant for session (p = 0.21), whereas some session differences were seen for flexion (p = 0.01), where session 1, 115.3 N was less than session 3, 126.4 N (p = 0.03). For %AUC, flexion values (%AUC 86.0) were greater than extension (%AUC 59.4) (p = 0.02). A similar effect was observed for TTF with flexion (125.0 seconds) having significantly greater TTF than extension (86.1 seconds). For peak force, the greatest SEM and MDC were achieved for extension (15.3 and 42.3 N), while flexion produced lower values (11.3 and 31.2 N). In contrast, for the endurance trials, SEM and MDC were greater in flexion than in extension. The findings from this study indicate that the neck musculature can be reliably assessed in a simulated contact posture. For peak force, extension provided more consistent measures across time as there seems to be a learning effect for flexion. Additionally, the SEM and MDC scores provide a useful tool for future assessment of neck strength and endurance.


Asunto(s)
Fútbol Americano/fisiología , Contracción Isométrica/fisiología , Músculos del Cuello/fisiología , Resistencia Física/fisiología , Adulto , Atletas , Femenino , Humanos , Masculino , Reproducibilidad de los Resultados , Adulto Joven
5.
J Sports Sci ; 32(4): 301-6, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24050682

RESUMEN

We investigated the effect of added load and intense exercise on jump and landing performance and ground reaction force (GRF) during landings where attentional demand was varied. Fifty-two males (37 ± 9.2 years, 180.7 ± 6.1 cm, 90.2 ± 11.6 kg, maximal aerobic fitness (VO(2max)) 50 ± 8.5 ml (.) kg(-1 .) min(-1), BMI 27.6 ± 3.1, mean ± s) completed a VO(2max) test. Experimental sessions were completed (≥4 days in between) in a randomised counterbalanced order, one while wearing body armour and appointments (loaded) and one without load (unloaded). A vertical jump, a drop landing concentrating on safe touchdown, a drop jump and a drop landing with an attentional distraction were performed. These were repeated 1 min after a 5-min treadmill run. Mean jump height decreased by 12% (P < 0.001) with loading and a further by 6% following the running task. Peak GRFs were increased by 13-19% with loading (P < 0.001) depending on the landing task demands and a further by 4-9% following intense exercise. The distracted drop landing had significantly higher GRFs compared to all other landings. Results demonstrate that added load impacts on jumping and landing performance, an effect that is amplified by prior intense exercise, and distraction during landing. Such increases in GRF apply to police officer performance in their duties and may increase the risk of injury.


Asunto(s)
Atención , Movimiento , Carrera , Estrés Mecánico , Análisis y Desempeño de Tareas , Soporte de Peso , Adulto , Fenómenos Biomecánicos , Prueba de Esfuerzo , Humanos , Masculino , Persona de Mediana Edad , Policia , Adulto Joven
6.
Int J Sport Nutr Exerc Metab ; 24(3): 333-40, 2014 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-24458212

RESUMEN

Effects of protein versus mixed macronutrient supplementation on total energy intake (TEI) and protein intake during an ad libitum diet were examined. Trained males undertook two, 2-week dietary interventions which were randomized, double blinded, and separated by 2 weeks. These were high-protein supplementation (HP: 1034.5 kJ energy, 29.6 g protein, 8.7 g fat and 12.3 g CHO) and standard meal supplementation (SM: 1039 kJ energy, 9.9 g protein, 9.5 g fat, and 29.4 g CHO) consumed daily following a week of baseline measures. Eighteen participants finished both interventions and one only completed HP. TEI (mean ± SD) was not different between baseline (11148 ± 3347 kJ) and HP (10705 ± 3143 kJ) nor between baseline and SM (12381 ± 3877 kJ), however, TEI was greater with SM than HP (923 ± 4015 kJ p = .043). Protein intake (%TEI) was greater with HP (22.4 ± 6.2%) than baseline (19.4 ± 5.4%; p = .008) but not SM (20.0 ± 5.0%). No differences in absolute daily protein intake were found. Absolute CHO intake was greater with SM than HP (52.0 ± 89.5 g, p = .006). No differences in fat intake were found. Body mass did not change between baseline (82.7 ± 11.2 kg) and either HP (83.1 ± 11.7 kg) or SM (82.9 ± 11.0 kg). Protein supplementation increases the relative proportion of protein in the diet, but doesn't increase the absolute amount of total protein or energy consumed. Thus some compensation by a reduction in other foods occurs. This is in contrast to a mixed nutrient supplement, which does not alter the proportion of protein consumed but does increase TEI.


Asunto(s)
Atletas , Carbohidratos de la Dieta/administración & dosificación , Proteínas en la Dieta/farmacología , Suplementos Dietéticos , Ingestión de Energía/efectos de los fármacos , Conducta Alimentaria/efectos de los fármacos , Fenómenos Fisiológicos en la Nutrición Deportiva , Adulto , Peso Corporal/efectos de los fármacos , Dieta , Grasas de la Dieta/administración & dosificación , Proteínas en la Dieta/administración & dosificación , Método Doble Ciego , Humanos , Masculino , Adulto Joven
7.
Nutrients ; 15(4)2023 Feb 10.
Artículo en Inglés | MEDLINE | ID: mdl-36839262

RESUMEN

The physiological, perceptual, and functional effects of dehydration may depend on how it is incurred (e.g., intense exercise releases endogenous water via glycogenolysis) but this basic notion has rarely been examined. We investigated the effects of active (exercise) heat- vs. passive heat-induced dehydration, and the kinetics of ad libitum rehydration following each method. Twelve fit participants (five females and seven males) completed four trials in randomised order: DEHydration to -3% change in body mass (∆BM) under passive or active heat stress, and EUHydration to prevent ∆BM under passive or active heat stress. In all trials, participants then sat in a temperate-controlled environment, ate a standard snack and had free access to water and sports drink during their two-hour recovery. During mild dehydration (≤2% ∆BM), active and passive heating caused comparable increases in plasma osmolality (Posm: ~4 mOsmol/kg, interaction: p = 0.138) and reductions in plasma volume (PV: ~10%, interaction: p = 0.718), but heat stress per se was the main driver of hypovolaemia. Thirst in DEHydration was comparably stimulated by active than passive heat stress (p < 0.161) and shared the same relation to Posm (r ≥ 0.744) and ∆BM (r ≥ 0.882). Following heat exposures, at 3% gross ∆BM, PV reduction was approximately twice as large from passive versus active heating (p = 0.003), whereas Posm perturbations were approximately twice as large from EUHydration versus DEHydration (p < 0.001). Rehydrating ad libitum resulted in a similar net fluid balance between passive versus active heat stress and restored PV despite the incomplete replacement of ∆BM. In conclusion, dehydrating by 2% ∆BM via passive heat stress generally did not cause larger changes to PV or Posm than via active heat stress. The heat stressors themselves caused a greater reduction in PV than dehydration did, whereas ingesting water to maintain euhydration produced large reductions in Posm in recovery and therefore appears to be of more physiological significance.


Asunto(s)
Deshidratación , Volumen Plasmático , Femenino , Humanos , Masculino , Deshidratación/etiología , Respuesta al Choque Térmico , Concentración Osmolar , Volumen Plasmático/fisiología , Agua , Equilibrio Hidroelectrolítico/fisiología
8.
Eur J Appl Physiol ; 112(5): 1827-37, 2012 May.
Artículo en Inglés | MEDLINE | ID: mdl-21915701

RESUMEN

Effectiveness of short-term acclimation has generally been undertaken using untrained and moderately-trained participants. The purpose of this study was to determine the impact of short-term (5-day) heat acclimation on highly trained athletes. Eight males (mean ± SD age 21.8 ± 2.1 years, mass 75.2 ± 4.6 kg, VO(2peak) 4.9 ± 0.2 L min(-1) and power output 400 ± 27 W) were heat acclimated under controlled hyperthermia (rectal temperature 38.5 °C), for 90-min on five consecutive days (T(a) = 39.5 °C, 60% relative humidity). Acclimation was undertaken with dehydration (no fluid-intake) during daily bouts. Participants completed a rowing-specific, heat stress test (HST) 1 day before and after acclimation (T(a) = 35 °C, 60% relative humidity). HST consisted 10-min rowing at 30% peak power output (PPO), 10 min at 60% PPO and 5-min rest before a 2-km performance test, without feedback cues. Participants received 250 mL fluid (4% carbohydrate; osmolality 240-270 mmol kg(-1)) before the HST. Body mass loss during acclimation bouts was 1.6 ± 0.3 kg (2.1%) on day 1 and 2.3 ± 0.4 kg (3.0%) on day 5. In contrast, resting plasma volume increased by 4.5 ± 4.5% from day 1 to 5 (estimated from [Hb] & Hct). Plasma aldosterone increased at rest (52.6 pg mL(-1); p = 0.03) and end-exercise (162.4 pg mL(-1); p = 0.00) from day 1 to 5 acclimation. During the HST T(re) and f(c) were lowered 0.3 °C (p = 0.00) and 14 b min(-1) (p = 0.00) after 20-min exercise. The 2-km performance time (6.52.7 min) improved by 4 s (p = 0.00). Meaningful physiological and performance improvements occurred for highly trained athletes using a short-term (5-day) heat acclimation under hyperthermia control, with dehydration.


Asunto(s)
Aclimatación/fisiología , Aldosterona/sangre , Regulación de la Temperatura Corporal/fisiología , Ejercicio Físico/fisiología , Respuesta al Choque Térmico/fisiología , Resistencia Física/fisiología , Atletas , Temperatura Corporal , Deshidratación/etiología , Prueba de Esfuerzo , Fiebre/fisiopatología , Humanos , Masculino , Volumen Plasmático , Adulto Joven
9.
Scand J Public Health ; 39(5): 492-500, 2011 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-21406480

RESUMEN

INTRODUCTION: A decrease in physical activity amongst adolescents has been observed and it is well documented that low levels of activity are associated with poor health. In an attempt to understand factors that influence physical activity (PA) in young people research was undertaken with high school students in New Zealand to identify preferred places for PA and establish factors that they felt influenced levels of PA. METHODS: One hundred males and 73 females in year nine (aged 12-13) in health and physical education classes completed mapping exercises in which they delineated favourite and least favourite places for PA, where they went on a particular Sunday, how they got there and what they did, and chosen after-school activities and how they got there. RESULTS: Open public spaces were the most favoured places for PA with a nearby beach and park most frequently cited. Specific physical activities, having fun, and having friends to do an activity with were the most frequently cited reasons for liking these places. An industrial harbour area, other schools, and cemeteries were the least favoured places. Less than 2% biked somewhere on the Sunday surveyed and only 23% walked somewhere. The majority were driven to activities by car and a similar reliance on cars was observed for after-school activities. CONCLUSIONS: A combination of environmental and social factors is important in both encouraging and discouraging PA and should be taken into account when seeking to enhance PA of young people.


Asunto(s)
Ambiente , Ejercicio Físico , Actividad Motora , Deportes , Adolescente , Conducta del Adolescente , Niño , Planificación Ambiental , Femenino , Humanos , Actividades Recreativas , Masculino , Nueva Zelanda , Educación y Entrenamiento Físico , Juego e Implementos de Juego
10.
PLoS One ; 16(1): e0244841, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33395691

RESUMEN

The objective of this study was to compare acute effects of prolonged sitting, prolonged standing and sitting interrupted with regular activity breaks on vascular function and postprandial glucose metabolism. In a randomized cross-over trial, 18 adults completed: 1. Prolonged Sitting; 2. Prolonged Standing and 3. Sitting with 2-min walking (5 km/h, 10% incline) every 30 min (Regular Activity Breaks). Flow mediated dilation (FMD) was measured in the popliteal artery at baseline and 6 h. Popliteal artery hemodynamics, and postprandial plasma glucose and insulin were measured over 6 h. Neither raw nor allometrically-scaled FMD showed an intervention effect (p = 0.285 and 0.159 respectively). Compared to Prolonged Sitting, Regular Activity Breaks increased blood flow (overall effect of intervention p<0.001; difference = 80%; 95% CI 34 to 125%; p = 0.001) and net shear rate (overall effect of intervention p<0.001; difference = 72%; 95% CI 30 to 114%; p = 0.001) at 60 min. These differences were then maintained for the entire 6 h. Prolonged Standing increased blood flow at 60 min only (overall effect of intervention p<0.001; difference = 62%; 95% CI 28 to 97%; p = 0.001). Regular Activity Breaks decreased insulin incremental area under the curve (iAUC) when compared to both Prolonged Sitting (overall effect of intervention P = 0.001; difference = 28%; 95% CI 14 to 38%; p<0.01) and Prolonged Standing (difference = 19%; 95% CI 4 to 32%, p = 0.015). There was no intervention effect on glucose iAUC or total AUC (p = 0.254 and 0.450, respectively). In normal-weight participants, Regular Activity Breaks induce increases in blood flow, shear stress and improvements in postprandial metabolism that are associated with beneficial adaptations. Physical activity and sedentary behaviour messages should perhaps focus more on the importance of frequent movement rather than simply replacing sitting with standing.


Asunto(s)
Presión Arterial/fisiología , Ejercicio Físico/fisiología , Hiperglucemia/metabolismo , Adulto , Área Bajo la Curva , Glucemia/metabolismo , Estudios Cruzados , Femenino , Glucosa/metabolismo , Hemodinámica/fisiología , Humanos , Insulina/metabolismo , Insulina Regular Humana/metabolismo , Masculino , Periodo Posprandial , Conducta Sedentaria , Sedestación , Posición de Pie , Triglicéridos/sangre , Caminata/fisiología
13.
J Nutr Metab ; 2020: 9382521, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33083056

RESUMEN

OBJECTIVE: To quantify energy drink consumption and influences affecting consumption in those who participate in or watch extreme sports. METHODS: An online survey, informed by focus groups, was administered via Quadrics®. Advertisement was via social media, emailing extreme sport clubs, flyers at extreme sport locations, and word of mouth. Participation was limited to those >18 y who watched and/or participated in extreme sports. The study was conducted in New Zealand, with international online availability. Variables measured comprised age, sex, energy drink consumption, reasons for their use, extreme sport viewing, advertising, and sponsorship. Logistic regression models were utilised. RESULTS: Amongst participants who completed the questionnaire (n = 247), the mean (SD) age was 26.2 (8.2) y, 40.5% were female, 57.9% consumed energy drinks, and 25.5% consumed >one per week. For every year older, odds of consuming energy drinks were 3.1% lower (p=0.04). A 31% increase in energy drink consumption for every single increase of viewing extreme sport per week was observed (p=0.009); however, reported viewing of advertising was not associated with increased consumption. CONCLUSIONS: A large proportion of extreme sport enthusiasts regularly consume energy drinks, especially younger adults. Extreme sport viewing, where energy drink sponsorship is common, appears to increase their consumption, even if not considered advertising by the viewers themselves.

14.
Eur J Clin Nutr ; 74(9): 1362-1365, 2020 09.
Artículo en Inglés | MEDLINE | ID: mdl-31969698

RESUMEN

The gut microbiota harvests energy from indigestible plant polysaccharides, forming short-chain fatty acids (SCFAs) that are absorbed from the bowel. SCFAs provide energy-presumably after easily digested food components have been absorbed from the small intestine. Infant night waking is believed by many parents to be due to hunger. Our objective was to determine whether faecal SCFAs are associated with longer uninterrupted sleep in infants. Infants (n = 57) provided faecal samples for determining SCFAs (7 months of age), and questionnaire data for determining infant sleep (7 and 8 months). Linear regression determined associations between SCFAs-faecal acetate, propionate and butyrate-and sleep. For each 1% higher propionate at 7 months of age, the longest night sleep was 6 (95% CI: 1, 10) minutes longer at both 7 and 8 months. A higher proportion of total faecal SCFA as propionate was associated with longer uninterrupted infant sleep.


Asunto(s)
Microbioma Gastrointestinal , Propionatos , Ácidos Grasos Volátiles , Heces , Humanos , Lactante , Sueño
15.
Eur J Appl Physiol ; 107(6): 659-70, 2009 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-19727796

RESUMEN

The purpose of this work was to investigate adaptation and decay from short-term (5-day) heat acclimation (STHA). Ten moderately trained males (mean +/- SD age 28 +/- 7 years; body mass 74.6 +/- 4.4 kg; VO2peak 4.26 +/- 0.37 l min(-1)) underwent heat acclimation (Acc) for 90-min on 5-days consecutively (T (a) = 39.5 degrees C, 60% RH), under controlled hyperthermia (rectal temperature 38.5 degrees C). Participants completed a heat stress test (HST) 1 week before acclimation (Acc), then on the 2nd and 8th day (1 week) following Acc (T (a) = 35 degrees C, 60% RH). Seven participants completed HSTs 2 and 3 weeks after Acc. HST consisted of 90-min cycling at 40% peak power output before an incremental performance test. Rectal temperature at rest (37.1 +/- 0.4 degrees C) was not lowered by Acc (95% CI -0.3 to 0.2 degrees C), after 90-min exercise (38.6 +/- 0.5 degrees C) it reduced 0.3 degrees C (-0.5 to -0.1 degrees C) and remained at this level 1 week later (-0.5 to -0.1 degrees C), but not two (0.1 degrees C -0.4 to 0.5 degrees C; n = 7) or 3 weeks. Similarly, heart rate after 90-min exercise (146 +/- 21 b min(-1)) was reduced (-13: -6 to -20 b min(-1)) and remained at this level after 1 week (-13: -6 to -20 b min(-1)) but not two (-9: 6 to -23 b min(-1); n = 7) or 3 weeks. Performance (746 s) increased 106 s: 59 to 152 s after Acc and remained higher after one (76 s: 31 to 122) but not two (15 s: -88 to 142 s; n = 7) or 3 weeks. Therefore, STHA (5-day) induced adaptations permitting increased heat loss and this persisted 1 week but not 2 weeks following Acc.


Asunto(s)
Aclimatación/fisiología , Trastornos de Estrés por Calor/fisiopatología , Calor , Adulto , Aldosterona/sangre , Ciclismo , Volumen Sanguíneo/fisiología , Monóxido de Carbono/sangre , Frecuencia Cardíaca/fisiología , Humanos , Hidrocortisona/sangre , Masculino , Consumo de Oxígeno/fisiología , Adulto Joven
16.
J Appl Physiol (1985) ; 105(1): 121-7, 2008 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-18436693

RESUMEN

This study was conducted to investigate effects of an acute sodium load on resting plasma volume (PV) and renal mechanisms across the menstrual cycle of endurance-trained women with natural (NAT) or oral contraceptive pill (OCP) controlled cycles. Twelve women were assigned to one of two groups, according to their usage status: 1) OCP [n = 6, 29 yr (SD 6), 59.4 kg (SD 3.2)], or 2) NAT [n = 6, 24 yr (SD 5), 61.3 kg (SD 3.6)]. The sodium load was administered as a concentrated sodium chloride/citrate beverage (164 mmol Na(+)/l, 253 mosmol/kgH(2)O, 10 ml/kg body mass) during the last high-hormone week of the OCP cycle (OCP(high)) or late luteal phase of the NAT cycle (NAT(high)) and during the low-hormone sugar pill week of OCP (OCP(low)) or early follicular phase of the NAT cycle (NAT(low)). The beverage ( approximately 628 ml) was ingested in seven portions across 60 min. Over the next 4 h, PV expanded more in the low-hormone phase for both groups (time-averaged change): OCP(low) 6.1% (SD 1.1) and NAT(low) 5.4% (SD 1.2) vs. OCP(high) 3.9% (SD 0.9) and NAT(high) 3.5% (SD 0.8) (P = 0.02). The arginine vasopressin increased less in the low-hormone phase [1.63 (SD 0.2) and 1.30 pg/ml (SD 0.2) vs. 1.82 (SD 0.3) and 1.57 pg/ml (SD 0.5), P = 0.0001], as did plasma aldosterone concentration ( approximately 64% lower, P = 0.0001). Thus PV increased more and renal hormone sensitivity was decreased in the low-hormone menstrual phase following sodium/fluid ingestion, irrespective of OCP usage.


Asunto(s)
Electrólitos/metabolismo , Hormonas Esteroides Gonadales/farmacología , Riñón/metabolismo , Volumen Plasmático/efectos de los fármacos , Descanso/fisiología , Sodio/farmacología , Adulto , Arginina Vasopresina/metabolismo , Ciclismo/fisiología , Agua Corporal/metabolismo , Anticonceptivos Hormonales Orales/farmacología , Etinilestradiol/farmacología , Femenino , Fase Folicular/fisiología , Hormonas/fisiología , Humanos , Levonorgestrel/farmacología , Fase Luteínica/fisiología , Modelos Estadísticos , Presión Osmótica , Progestinas/farmacología
17.
Int J Sports Physiol Perform ; 13(9): 1199-1207, 2018 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-29651857

RESUMEN

PURPOSE: To examine the movement and physiological demands of rugby union officiating in elite competition. METHODS: Movement demands of 9 elite officials across 12 Super Rugby matches were calculated, using global positioning system devices. Total distance (in m), relative distance (in m·min-1), and percentage time spent in various speed zones were calculated across a match. Heart-rate (HR) responses were also recorded throughout each match. Cohen d effect sizes were reported to examine the within-match variations. RESULTS: The total distance covered was 8030 (506) m, with a relative distance of 83 (5) m·min-1 and with no differences observed between halves. Most game time was spent at lower movement speeds (76% [2%]; <2.0 m·s-1), with large effects for time spent >7.0 m·s-1 between halves (d = 2.85). Mean HR was 154 (10) beats·min-1 (83.8 [2.9]%HRmax), with no differences observed between the first and second halves. Most game time was spent between 81%HRmax and 90%HRmax (40.5% [7.5%]) with no observable differences between halves. Distances covered above 5.1 m·s-1 were highest during the first 10 min of a match, while distance at speeds 3.7 to 5 m·s-1 decreased during the final 10 min of play. CONCLUSIONS: These findings highlight the highly demanding and intermittent nature of rugby union officiating, with only some minor variations in physical and physiological demands across a match. These results have implications for the physical preparation of professional rugby union referees.


Asunto(s)
Fútbol Americano/fisiología , Carrera/fisiología , Adulto , Conducta Competitiva/fisiología , Sistemas de Información Geográfica , Frecuencia Cardíaca , Humanos , Monitoreo Fisiológico , Movimiento/fisiología , Acondicionamiento Físico Humano , Factores de Tiempo , Estudios de Tiempo y Movimiento
18.
J Sports Med Phys Fitness ; 58(7-8): 1078-1089, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-28409514

RESUMEN

BACKGROUND: Neck strength has been reported to reduce the incidence of concussions and neck injuries. However, little is known about how neck strength changes over a playing season. The aim of this study was to understand the impact a 20-week rugby season has on neck strength, neck pain (NP) and neck stiffness (NS) in a cohort of rugby players, relative to a non-contact control group. METHODS: This prospective cohort study employed a fixed-frame dynamometer to measure neck strength in a simulated contact posture in rugby players (N.=32) and controls (N.=15). During each assessment, participants performed a single maximal voluntary contraction in extension, flexion, left (LtFlx) and right lateral flexion (RtFlx). To quantify neck dysfunction, "current," "average," and "worst" NP and NS were measured using visual analogue scales. RESULTS: Post-season improvements (35.3-59.1 N) in neck strength were observed for the forwards for all measured directions (P<0.01), and were significant when compared to controls. For the backs, improvements were seen in extension, flexion and LtFlx (P=0.01-0.05), with only extension (29.8 N) and flexion (35.14 N) remaining significant when contrasted against the controls. The controls' neck strength remained unchanged over the season. Despite improvements in peak force, NP increased (all three measures) for the forwards (P=0.01-0.04), while only current (P=0.03) and worst NP (P=0.04) increased for the backs. Unexpectedly, NS remained unchanged for the forwards, while backs reported increases for all three measures (P=0.01-0.02). CONCLUSIONS: A season of rugby resulted in neck strength adaptations in the rugby players. Despite these improvements, increased levels of NP and NS were reported.


Asunto(s)
Fútbol Americano/fisiología , Fuerza Muscular/fisiología , Cuello/fisiología , Adulto , Estudios de Casos y Controles , Humanos , Masculino , Dolor de Cuello/fisiopatología , Estudios Prospectivos , Rango del Movimiento Articular/fisiología , Autoinforme , Adulto Joven
19.
Temperature (Austin) ; 5(2): 175-183, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-30393753

RESUMEN

Heat is a major stressor during exercise, though its value in driving adaptation is not well understood. Muscle heating can upregulate pathways facilitating protein synthesis and could thereby enhance effects of exercise training, however, few studies have investigated this possibility. We examined whether heating active muscle during resistance training differentially affected physical and functional adaptations. Within a randomised contralateral-limb control study, ten healthy, resistance-untrained individuals (21 ± 3 y; 5 female) completed 30 sessions of progressive resistance training (12 weeks), performing 4 × 8 unilateral knee extensions at 70% of 1RM. One randomly-allocated thigh was heated during, and for 20 min after, each session using an electric pad eliciting muscle temperatures of >38 °C (HOT); the contralateral limb remained unheated (CON). Training intensity was progressed using 4-weekly strength assessments. Quadricep lean mass (measured using DXA) increased by 15 ± 7% in HOT (p = 0.00) and 15 ± 6% in CON (p = 0.00); the difference being trivial (p = 0.94). Peak isokinetic torque at 90°.s-1 increased by 30 ± 25% (HOT; p = 0.00) and 34 ± 33% (CON; p = 0.01), with no difference (p = 0.84) between limbs. Rate of torque development increased ∼40%, with no difference between limbs (p = 0.73). The increase in 3-RM strength was also similar in HOT (75 ± 16%) and CON (71 ± 14%; p = 0.80 for difference). No differences in mass or strength changes were evident between sexes. In conclusion, supplemental heating of active muscle during and after each bout of resistance training showed no clear positive (or negative) effect on training-induced hypertrophy or function.

20.
Nutrients ; 10(2)2018 Jan 26.
Artículo en Inglés | MEDLINE | ID: mdl-29373503

RESUMEN

Regular activity breaks increase energy expenditure; however, this may promote compensatory eating behaviour. The present study compared the effects of regular activity breaks and prolonged sitting on appetite. In a randomised, cross-over trial, 36 healthy adults (BMI (Body Mass Index) 23.9 kg/m² (S.D. = 3.9)) completed four, two-day interventions: two with prolonged sitting (SIT), and two with sitting and 2 min of walking every 30 min (RAB). Standardized meals were provided throughout the intervention, with an ad libitum meal at the end of Day 2. Appetite and satiety were assessed throughout both days of each intervention using five visual analogue scales. The five responses were combined into a single appetite response at each time point. The area under the appetite response curve (AUC) was calculated for each day. Intervention effects for appetite response AUC and ad libitum meal intake were tested using linear mixed models. Appetite AUC did not differ between interventions (standardised effect of RAB compared to SIT: Day 1: 0.11; 95% CI: -0.28, 0.06; p = 0.212; Day 2: 0.04; 95% CI: -0.15, 0.24; p = 0.648). There was no significant difference in energy consumed at the ad libitum lunch meal on Day 2 between RAB and SIT. Interrupting prolonged sitting with regular activity breaks does not acutely influence appetite or volume of food consumed, despite inferred increases in energy expenditure. Longer-term investigation into the effects of regular activity breaks on energy balance is warranted.


Asunto(s)
Regulación del Apetito , Conducta Sedentaria , Salud Urbana , Caminata , Adolescente , Adulto , Estudios Cruzados , Ingestión de Energía , Metabolismo Energético , Ejercicio Físico , Femenino , Humanos , Masculino , Comidas , Nueva Zelanda , Respuesta de Saciedad , Autoinforme , Factores de Tiempo , Adulto Joven
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