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Acute progressive hypoxia: effects on endurance performance and its physiology
Full text linkIntroduction Hypoxia is defined as a reduction in the amount of oxygen (O2) available to any cell, tissue, or organism (Semenza, 2009). Research examined the effects of this reduction on endurance performance [see (Fulco et al., 1998) for review] and the benefits deriving from the exposure (and training) in hypoxia on the sea level endurance performance [see (Millet et al., 2010) for review]. However, endurance and ultra-endurance performances can also be performed in hypoxic environments. This is an intrinsic feature of those performances that either start from an altitude level and finish at a higher one or where the altitude profile changes during the race (e.g. uphill cycling time trial, running vertical kilometres, etc.). Accordingly, to date less is known about the determinants of performance where the severity of hypoxia changes during the trial (i.e. Progressive Hypoxia, PH). Therefore, the aim of this project was to investigate the effects of acute progressive hypoxia on the endurance performance and fatigue. A secondary aim was to determine the main physiological responses during these tasks in PH at different intensities of effort. Study I There are competitions like the mass start events (e.g. running and ski mountaineering vertical kilometres, cycling stages with uphill arrival, etc.) that take place in hypoxia, or even in progressive hypoxia, with the final high intensity effort at a higher altitude compared with the starting one. The aim of the study was to understand if a different hypoxic stimulus, during a submaximal cycling exercise (50% of relative Peak Power Output, PPO) impairs the high intensity performance of the final high intensity effort. After a maximal ramp test to obtain the PPO and baseline measurements of endurance performance (time to exhaustion, TTE) in a non-fatigued state (both in normoxia and in hypoxia) 8 subjects completed an 1-hour cycling protocol in normoxia (at 50% of PPO obtained in normoxia, N), constant hypoxia and progressive hypoxia (FiO2 = 13.4%, and FiO2 starting from 16.25 to 13.4%, at 50% of PPO obtained in hypoxia, Hcost and HH, respectively). TTE duration was reduced both after the N and Hcost session (-27.9% P=0.03 and -21.6% P=0.007, respectively) with no effect after HH. Higher oxygen saturation (SpO2) was observed during cycling exercise in N compared to the other two conditions. Hcost resulted in a lower SpO2 compared to HH, until the end of the 1-h bout, where Hcost and HH presented similar SpO2 due to similar altitude levels reached. Oxygen consumption was similar during the HH and Hcost condition, but Hcost is lower than in N (P=0.03). Rate of perceived exertion was similar in the three conditions. The primary finding of this study was that an impairment of ~25% in the endurance performance (tested through a TTE test and compared to a non-fatigued trial at baseline) was observed after both a normoxic (P=0.03) and a constant hypoxic (P=0.007) task; no effects after 1-h in HH. A possible explanation to the different effect of HH and Hcost on TTE performance can be related to the hypoxic dose (5.25 VS 3.75 kilometres/hour in Hcost VS HH, respectively). Study II There are competitions that take place in progressive hypoxia at a submaximal intensity throughout the entire duration with the final part of the race at a higher altitude compared to the starting one. The aim of this study was to investigate the effects of an 1-h exposure at different cycling submaximal intensities at progressive hypoxia on fatigue and endurance performance (tested through a Time To Exahustion, TTE). Peak power output (PPO) and baseline duration in a TTE were obtained in a non-fatigued state (both in normoxia and in hypoxia) in 11 subjects. Subsequently, in three separated days, they completed an 1-h protocol under the same progressively hypoxic stimulus (FiO2 starting from 16.25 to 13.4%, simulating an increase in altitude from 2000 to 3500 m) at different intensities: no effort (H_NoPO), 50% of the PPO in hypoxia (HH) and 50% of the PPO in normoxia (HN). Oxygen consumption, heart rate, blood lactate, cerebral blood flow and pulse oxygen saturation were monitored during each session. Neuromuscular fatigue was assessed pre and post the 1-h intervention as well as after the subsequent TTE. We observed a reduced duration of TTE only after 1-h HN, when compared to baseline and H_NoPO (-37.2% P<0.001 and -30.8% P=0.016). One of the reason of this impairment in performance can be the higher blood lactate accumulation and the higher RPE during 1-h HN. The general reduction in SpO2 during the three interventions may be one of the causes of the reduction in voluntary activation, as an index of central fatigue, even though cerebral blood flow increased with time without any differences between conditions. The novelty of this study was to investigate the acute effects on performance and fatigue at different submaximal intensities when athletes are exposed to a progressively increased hypoxia. The main finding was that the endurance performance (assessed by means of TTE, that can be considered as the final high intensity effort at a higher altitude compared with the starting one) was only compromised after 1-h of cycling at 50% of the absolute peak power output obtained in normoxia. Therefore, it can be a good practice to test athletes that need to perform at altitude, in simulated condition. General conclusion Progressive hypoxia is a condition encountered during several endurance and ultra endurance performances. The understanding of the effects driven by a PH exposure at different intensities on a subsequent endurance performance can be useful for coaches and athletes that need to plan and pace their efforts in similar environments. We need to be conscious that in altitude, and especially in PH, the threshold between choosing the correct intensity of an effort and the intensity that can results in a subsequent impairment during an endurance performance (TTE) is really thin. Therefore, it can be a good practice to test athletes that need to perform at altitude, in a similar condition. Finally, we can conclude that a small step forward in the understanding of efforts during a progressive hypoxic stimulus has been provided. More work is needed, and the next step could be to study PH in field performances
Application to cycling of a bioenergetic model: Towards a multi-level biomechanical model for global cyclist performance analysis
No full textModels of bioenergetic systems are developed to explain how a biological system behaves while interacting with the environment. Recent attempts in sport science research advocate the evidence-based training prescription and performance assessment and help in translating laboratory-based research into real world practice by the means of bioenergetic models. Such models have been developed for cycling activity for constant work rate or intermittent exercise for a single training session (e.g. critical power CP model and reconstitution of the anaerobic work capacity, (Chidnok et al., 2012, Medicine & Science in Sports and Exercise, 44(5), 966-976)), as well as for describing how the performance capacity changes over time (Clarke & Skiba, 2013: Advances in Physiological Education, 37, 134-152). The model here adopted (Moxnes et. al, 2012, Theoretical Biology and Medical Modelling, 9:29) claims to predict both oxygen consumption (V’O2) and lactate production [La]’ dynamically at a given power output requirement. In this work we model the bioenergetics processes involved in human exercise and recovery for the case of a cyclist in outdoor training
Cost of force generation as an index of performance ability in cross coun try skiers
No full textMetabolic power depends on mean force applied to the ground during a cycle , on rate of force application and on cost of force generation. This cost is constant at different speeds and describe the amount of energy spent to perform a Newton of muscular force
In a sport where energy consumption, muscular capabilities and force application strategies can influence performance capabilities, the computation of cost of force generation could be a good index of performance ability
Energy cost of running in middle-aged amateur runners: Is it affected by fatigue?
No full textBackground: The energy cost of running per unit mass and distance (Cr) is reported to increase or to remain constant after a fatigue test in young healthy adults. No studies were performed on master athletes about this topic.
Research question: Does the energy cost of running increase after a half marathon in a group of master athletes?
Type of study: Pre-Post single group design.
Methods: Ten healthy master athletes took part in the experiment. The experimental protocol involved an incremental test to exhaustion, a half marathon simulation and two sessions of energy cost assessments before and after the race simulation.
Results: Neither comparing fatigue to no-fatigue conditions (p>0.05) nor as a function of the running speed (p>0.05) could a change in the group mean energy cost be revealed.
Conclusions: The energy cost of running is not affected by a half marathon race within a group of master athletes
COM displacement influences the energetic cost of lococmotion during the double poling technique
No full textDouble poling technique (DP) is a particular type of skiing locomotion due to the extensive use of the upper body. Cost of locomotion is generally related to metabolic adaptations to training, but also biomechanical strategies can concur to set the amount of energy spent to travel at a given speed. The aim of this investigation was to analyze metabolic and biomechanical characteristics of two differently skilled groups of cross-country skiers, in relation to the energetic cost of DP locomotion
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
Development of a Low-Cost System for Analytical Performance Analysis in Alpine Skiing
No full textMonitoring the performance of athletes during training is crucial for technical sports such as alpine skiing. Recent technological advancements have led to the development of wearable devices capable of monitoring athletes in real time and providing trainers with comprehensive performance reports. In this study, we present a preliminary investigation into the feasibility of a Global Navigation Satellite System (GNSS) tracking system for analyzing gate-to-gate performance in alpine skiing training. The system utilizes Real-Time Kinematic (RTK) GNSS technology for precise satellite positioning. An Android application designed for this purpose collects the corrected position data and transmits it to the cloud. A Matlab script elaborates the data and generates the gate-to-gate trajectory analysis. The system was tested with ten skiers at the national level and compared against a professional timing system. The results demonstrate the feasibility and usability of this solution, indicating its potential for implementation in alpine ski training
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
Exercising at the time of the COVID-19 pandemic: acute physiological, perceptual and performance responses of wearing face masks during sports activity
Full text linkBackground: The COVID-19 pandemic requires the adoption of strict preventive measures, such as wearing a protective face mask , but few studies investigated its impact during exercise. We investigated the effects of wearing a protective face mask while exercising at different intensities and verified whether differences between two types of protective face masks exist. Methods: Twenty subjects performed 4-min running at 8 km•h-1 and at 10 km•h-1, 8 x 90-m Intermittent running bouts and the Yo-Yo Intermittent Recovery Test Level-1, while wearing either a surgical mask, a sports-reusable mask or no mask. Physiological responses (HR, [La], SpO2), overall and breathlessness perceived exertion and YYIRT1-distance were assessed. Results: Breathlessness RPE was greater with surgical than without mask at the end of the run at 8 km•h-1 (+7.18 [3.21, 11.50]) and with both surgical and sports-reusable mask than without mask at the end of the run at 10 km•h-1 (+8.09 [4.09, 12.60] and +8.21 [4.53, 12.70]) and intermittent exercise (+11.10 [6.41, 16.10] and +10.50 [6.18, 15.30]). Overall RPE was greater with surgical than without mask at the end of the run at 8 (+3.71 [1.15, 6.91]) and 10 km•h-1 (+5.29 [2.26, 8.85]). Furthermore, YYIRT1 performance was lower with surgical (-150 m [44, 240]) and sports-reusable mask (-201 m [108, 286]) than without mask. Conclusions: Regardless of exercise intensity and mask type, wearing a protective face mask mostly affects perceptual responses, also causing a performance reduction during maximal exercise. These findings must be considered when prescribing/practicing exercise while wearing a protective face mask
Validity of the SenseWear ArmbandTM to Assess Energy Expenditure in Graded Walking
No full textBackground: Accurate assessments of physical activity and energy expenditure (EE) are needed to advance research on positive and negative graded walking. Purpose: To evaluate the validity of two SenseWearTM Armband monitors (Pro3 and the recently released Mini) during graded walking. Methods: Twenty healthy adults wore both monitors during randomized walking activities on a motorized treadmill at seven grades (0%, ±5%, ±15% and ±25%). Estimates of total EE from the monitors were computed using different algorithms and compared to values derived from indirect calorimetry methodology using a 2-way mixed model ANOVA (Device x Condition), correlation analyses and Bland-Altman plots. Results: There was no significant difference in EE between the two armbands in any of the conditions examined. Significant main effects for device and condition as well as a consistent bias were observed during positive and negative graded walking, with a greater over- and under-estimation at higher slope. Conclusions: Both the armbands produced similar EE values and seem to be not accurate in estimation of EE during activities involving uphill and downhill walking. Additional work is needed to understand factors contributing to this discrepancy and to improve the ability of these monitors to accurately measure EE during graded walking
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