1,720,996 research outputs found
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
Oxygen consumption and muscle fatigue induced by whole-body electromyostimulation compared to equal-duration body weight circuit training
No full textBackground: Whole-body electromyostimulation (WB-EMS) has become increasingly popular under the promise to offer a time-saving and effective exercise protocols. Few studies estimating the training intervention intensity of WB-EMS are available in the literature. Aim: The aim of this study was first to estimate the metabolic demand and muscle fatigue induced by a training session with WB-EMS, and second to compare them to a control intervention. Methods: Ten young participants performed two training sessions: an experimental condition constituted by five exercises with superimposed WB-EMS and a control condition constituted by five body weight exercises. Both sessions lasted 15 min and were based on isometric intermittent contraction (6 of contraction interspersed by 4 s of rest). Muscle fatigue was assessed by determining the force decrease in the following tests: isometric mid-thigh pull; plyometric push-up; counter-movement jump. Oxygen consumption and energy expenditure were recorded by measuring respiratory gases exchange to quantify the metabolic demand of the exercises. Results: The WB-EMS intervention required greater volume of oxygen consumed (WB-EMS 1584 ± 251 ml/min; control 1465 ± 216 ml/min, p = 0.006) and energy expenditure (WB-EMS 470 ± 71 kcal/h; control 438 ± 61 kcal/h, p = 0.013) than in control intervention. Overall, the WB-EMS training induced muscle fatigue (all PRE vs POST tests p ≤ 0.02) whereas the body weight exercises did not (all p > 0.14). Conclusions: These results indicate that WB-EMS intervention constituted a vigorous physical activity. The WB-EMS required also a greater metabolic demand and greater muscle fatigue than a traditional body weight circuit training. Thus, WB-EMS can be considered as an alternative training tool for physically active individuals. © 2016, Springer-Verlag Italia
Talent development in young cross-country skiers: longitudinal analysis of anthropometric and physiological characteristics
Full text linkIntroduction: Very little is known about talent development and selection processes in young cross-country skiers. Aim: (1) to analyze the effect of age on anthropometric and physiological parameters in medium-to-high level cross-country skiers during the late teenage period; (2) to describe parameters' trend in selected talents after the late teenage period; (3) to define which characteristics during the late teenage period could discriminate against further talent selection. Method: We found 14 male (M) and nine (F) athletes in our database, identified as talents by regional teams during the late teenage period, who performed the same diagonal-stride roller-skiing incremental test to exhaustion at 17 and 18 years old. Of these, four M and three F teenagers performed four further evaluations, and were selected by the national team. Age effect during the late teenage period was verified on anthropometric and physiological parameters measured at maximal intensity (MAX), first (VT1), and second (VT2) ventilatory thresholds, and 3° and 6° of treadmill incline. An observational analysis allowed to evaluate parameters' trend after the late teenage period in selected athletes, and to determine possible characteristics early discriminating further selection. Results: During the late teenage period, height, weight, and BMI was still raising in M as well as V'O2 at VT2 and 6° of treadmill incline (all P > 0.05). In F, mass-scaled V'O2 MAX increased while heart rate (HR) at MAX and VT2 decreased (all P > 0.05). Since the late teenage period, all selected males showed maximal ventilation volumes, absolute V'O2 at MAX, VT1, and VT2 that were within or above the 75th percentile of their group; the same was found in selected females for mass-scaled V'O2 MAX, VT1, and VT2 time. After the late teenage period, all selected athletes showed an increasing trend for VT2 time, while a decreasing trend for sub-maximal energetic cost, %V'O2 and HR. Discussion: During the late teenage period, males are still completing their maturation process. Since the late teenage period, some physiological parameters seem good indicators to early discriminate for further talents. A progressive increase in skiing efficiency was demonstrated in developing talents of both sexes after the late teenage period
Moderate heart rate-matched hypoxic exercise: autonomic and cardiovascular responses to different degrees of hypoxic stress
Full text linkPurpose This study aims to assess the impact of HR-matched exercises under varying hypoxic stress levels on exercise and post-exercise autonomic and cardiovascular responses. Methods Twelve moderately aerobically trained healthy men (mean age: 23 +/- 2 years, height: 179 +/- 8 cm, weight: 71.2 +/- 9.9 kg, BMI: 22.2 +/- 2.2 kg/m(2), VO(2)max: 53.1 +/- 4.2 mL/min/kg) completed an interval exercise session at 75% of their normoxic maximum heart rate (75%HRmax) under three hypoxic conditions: FiO(2) = 16.2% (2000 m a.s.l; H16), FiO(2) = 14.3% (3000 m a.s.l; H14), and FiO(2) = 12.6% (4000 m a.s.l; H12). Each session included 5 min of seated rest, a 5-min sub-maximal load warm-up, and five 5-min work intervals with 1-min passive recovery periods. Results During hypoxic exercise, RMSSD decreased significantly following the first bout coinciding with an increase in heart rate. The RMSSD increase during 60-s recovery intervals was significantly lower after the 4th and 5th bouts compared to the 1st and 2nd bouts (p < 0.05). At 15 min post-exercise, mean RR, systolic blood pressure and stroke volume decreased. No changes were observed in cardiac output or baroreflex sensitivity. At 60 min post-exercise, SDNN, RMSSD, mean arterial pressure and diastolic blood pressure increased significantly compared to 15 min post-exercise. No condition or interaction differences were found. Conclusion Despite the decreased oxygen saturation with increased hypoxia levels, HR-matched interval exercise induced similar cardiac and autonomic responses across all hypoxic conditions. Baseline cardiac autonomic function and hemodynamics recovered within 60 min with no impact of hypoxia on baroreflex sensitivity
Combined effects of normobaric hypoxia and cold on respiratory system responses to high-intensity exercise
Full text linkCold temperatures (<-15°C) increase exercise-induced bronchoconstriction (EIB), while hypoxic-induced hyperventilation exacerbates respiratory muscle fatigue for a given exercising task. This study aimed to determine the individual and combined effects of cold and normobaric hypoxia on the respiratory system responses to high-intensity exercise. Fourteen trained male runners ( V̇O2max : 64 ± 5 mL/kg/min) randomly performed an incremental cardiopulmonary exercise test (CPET) to volitional exhaustion under four environmental conditions: normothermic (18°C) normoxia ( FIO2 : 20.9%) and hypoxia ( FIO2 : 13.5%), and cold (-20°C) normoxia and hypoxia. Ventilatory responses during exercise and lung function (LF), maximal inspiratory (MIP) and expiratory (MEP) pressure measurements before and after exercise were evaluated. Volume of air forcefully exhaled in 1 s (FEV1), FEV1/forced vital capacity (FVC), peak expiratory flow, forced expiratory flow during the mid (25-75%) portion of the FVC, and maximal expiratory flow at 50% of FVC were affected by cold exposure. No significant pre- to post-exercise change in MIP and MEP was found, independent of environmental conditions. Greater LF impairments in cold-normoxia and coldhypoxia were associated with the lowest peak ventilatory responses during exercise. Cold exposure was found to negatively impact peak ventilatory responses and post-exercise LF, further highlighting a relationship between EIB presence and the blunted ventilatory response in the cold. Respiratory muscle strength remained unchanged after exercise regardless of the environmental condition, suggesting no detrimental effect of hypoxia on this parameter when intermittent short-duration high-intensity exercises are performed. Future studies should investigate the combined cold-hypoxic effect on longer exercise durations at a sustained high intensity, accounting for differences between normobaric and hypobaric hypoxia exposures
State-of-the art concepts and future directions in modelling oxygen consumption and lactate concentration in cycling exercise
No full textPurpose: Bioenergetic models are used in cycling to estimate the acute physiological response in terms of oxygen consumption (V ̇ O2) and lactate concentration ([La]). First, our aim is to review the bioenergetic modelling literature, presenting historical evolution of concepts, techniques and related limitations. Second, our aim is to discuss how and where new approaches can stem and evolve. Methods: This is a narrative review, where different modelling solutions are compared and qualitatively discussed. First, the principal features of the V ̇ O2 and [La] kinetics are presented, and then the models available in the literature are compared in light of what aspects of the physiological responses they can describe. Results: Currently, models can detect most features of V ̇ O2 and [La] kinetics, but no single existing model appears appropriate for every exercising conditions. Limitations hindering the creation of an ultimate model are: the large variability of an exercise, the required mathematical complexity, and lack of reliable physiological data. To overcome these issues, new modelling solutions are being explored in the emerging AI technologies. However, in AI-models, parameters do not have direct physiological meaning and require massive amounts of experimental data for parameter calibration. Conclusions: Despite the great efforts made by model developers and exercise physiologists, universal modelling solutions for the variety of potential exercising conditions remain unavailable. At present, further research is needed to assess the accuracy and predictive power of AI models to move the method forward in our field, as it is being done so in many others. © 2019, Springer-Verlag Italia S.r.l., part of Springer Nature
The energetics during the world most challenging mountain ultramarathon: a case study
No full textThe energy requirements during ultra-endurance events are likely to be at the extremes ofhuman tolerance (Millet and Millet, 2012). This is of further importance for extreme mountain ultra-marathon (MUM), where the ultra-long distance performance is coupled to run and/or walk on mountain trails with considerable positive and negative elevation change. For instance, it was shown that after the world’s most challenging MUM the energy cost of uphill running decreased, likely due to changes in the uphill-running step mechanics that lead to a ‘smoother’ and more economical running style (Vernillo et al., 2013). However, that study focused only on longitudinal (i.e., pre-post) changes. Thus, there are few data examining the physiological changes during a MUM with a high fatiguing potential in ecologically valid environments. Accordingly, we report the case of an experienced MUM runner who was participating in the world’s most challenging MUM with the aim to provide the first data about the energy requirements as well as the physiological adaptations of MUM
Natural images and hypoxia: a study on the effects of exposure to natural images in simulated high-altitude conditions.
No full textA high mountain environment is characterized by a decrease in the ambient partial pressure of oxygen (hypoxia), representing a stressful condition capable of altering cognitive functions and emotional states (Ruffini & Cera, 2020). Previous studies have shown that exposure to nature is associated with greater well-being (Bowler, 2010) and promotes recovery from stressful events (Berto, 2014). This contribution aims to examine the psychological and physiological effects of exposure to nature in a controlled laboratory setting, and its potential role as a moderator of the negative effects of hypoxia. In a randomized within-subjects design, participants are shown images of natural or urban environments for 10 minutes while exposed to a normoxia (i.e., air oxygen pressure at sea level) or hypoxia (i.e., air oxygen pressure at 4200 m altitude) laboratory condition. Measures of emotional states are collected before (T1) and after exposure to the images (T2). At the same time, physiological indices (e.g., heart rate, heart rate variability, blood pressure, and ventilatory response) are monitored for the entire experiment duration. Preliminary results on a partial sample confirm the effect of hypoxia on emotional states, with higher levels of negative emotions and lower levels of positive emotions in the hypoxia condition. Finally, natural images appear to moderate this effect; results show a reduction in negative emotions and an increase in positive emotions in both conditions (I.e., normoxia and hypoxia). The potential implications of our findings will be discussed
Assessing recovery after high-intensity anaerobic exercise: a comparison between physiological and psychological measures
No full textDrawing from established theories in environmental psychology, including Stress
Reduction Theory and Attention Restoration Theory, which underscore the restorative
potential of natural environments, we seek to understand the e>ects of restorative
environments on athletic performance and health.
This study will assess the reliability of psychological measures compared to
physiological measures, examining the influence of exposure to restorative natural
environments on athlete recovery following anaerobic exercise through a mixed
design. Data collection is still ongoing in three di>erent countries: Italy, Spain and
Denmark.
Participants engage in anaerobic exercise on stationary bikes and are then exposed to
a 3-minute video showing either a restorative natural environment or an urban non-
restorative environment. The restorativeness of both videos was previously assessed
on a di>erent sample. Pre and post-exercise measures encompass muscular,
metabolic, and autonomic indices to comprehensively assess physiological
responses. Psychological measures include core a>ect, perceived e>ort, state
anxiety, psychological restoration and perceived restorativeness of the environment.
Through rigorous experimental design and meticulous data collection, this study aims
to elucidate whether exposure to restorative natural environments yields discernible
impacts on physiological markers of recovery in athletes.
Findings from this investigation will contribute to clarifying the e>ectiveness of
psychological and physiological measures within the framework of studying the
restorativeness benefits of natural environments on wellbeing and mental health.
Furthermore, novel insights into the potential physiological benefits of restorative
environments within the context of athletic recovery offer valuable implications for
sports science and performance optimisation strategies
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