Understanding soccer players' match-related fatigue and recovery profiles likely helps with developing conditioning programs that increase team performance and reduce injuries and illnesses. In order ...to improve match recovery (the return-to-play process and ergogenic interventions) it is also pivotal to determine if match simulation protocols and actual match-play lead to similar responses.
(1) To thoroughly describe the development of fatigue during actual soccer match play and its recovery time course in terms of physiological, neuromuscular, technical, biochemical and perceptual responses, and (2) to determine similarities of recovery responses between actual competition (11 vs. 11) and match simulations.
A first screening phase consisted of a systematic search on PubMed (MEDLINE) and SportDiscus databases until March 2016. Inclusion criteria were: longitudinal study with soccer players; match or validated protocol; duration > 45 min; and published in English.
A total of 77 eligible studies (n = 1105) were used to compute 1196 effect sizes (ES). Half-time assessments revealed small to large alterations in immunological parameters (e.g. leukocytes, ES = 1.9), a moderate decrement in insulin concentration (ES = - 0.9) and a small to moderate impairment in lower-limb muscle function (ES = - 0.5 to - 0.7) and physical performance measures (e.g. linear sprint, ES = - 0.3 to - 1.0). All the systematically analyzed fatigue-related markers were substantially altered at post-match. Hamstrings force production capacity (ES = - 0.7), physical performance (2-4%, ES = 0.3-0.5), creatine kinase (CK, ES = 0.4), well-being (ES = 0.2-0.4) and delayed onset muscle soreness (DOMS, ES = 0.6-1.3) remained substantially impaired at G + 72 h. Compared to simulation protocols, 11 vs. 11 match format (CK, ES = 1.8) induced a greater magnitude of change in muscle damage (i.e. CK, ES = 1.8 vs. 0.7), inflammatory (IL-6, ES = 2.6 vs. 1.1) and immunological markers and DOMS (ES = 1.5 vs. 0.7) than simulation protocols at post-assessments. Neuromuscular performances at post-match did not differ between protocols.
While some parameters are fully recovered (e.g. hormonal and technical), our systematic review shows that a period of 72 h post-match play is not long enough to completely restore homeostatic balance (e.g. muscle damage, physical and well-being status). The extent of the recovery period post-soccer game cannot consist of a 'one size fits all approach'. Additionally, the 'real match' (11 vs. 11 format) likely induces greater magnitudes of perceptual (DOMS) and biochemical alterations (e.g. muscle damage), while neuromuscular alterations were essentially similar. Overall, coaches must adjust the structure and content of the training sessions during the 72-h post-match intervention to effectively manage the training load within this time-frame.
Inhomogeneous Magnetization Transfer (ihMT) is a development from the MT MRI technique. IhMT can be considered as a dipolar order relaxation time (T1D) weighted imaging modality whose signal has ...shown an enhanced selectivity for myelin-rich structures. However, a formal validation of the ihMT sensitivity relative to a gold standard myelin density measurement has not yet been reported. To address this need, we compared ihMT MRI with green fluorescence protein (GFP) microscopy, in a study performed on genetically-modified plp-GFP mice, considered as a reference technique for myelin-content assessment. Various ihMT protocols consisting of variable T1D-filtering and radiofrequency power temporal distributions, were used for comparison with fluorescence microscopy. Strong and significant linear relationships (r2 (0.87–0.96), p < 0.0001) were found between GFP and ihMT ratio signals across brain regions for all tested protocol variants. Conventional MT ratios showed weaker correlations (r2 (0.24–0.78), p ≤ 0.02) and a much larger signal fraction unrelated to myelin, hence corresponding to a much lower specificity for myelin. T1D-filtering reduced the ihMT signal fraction not attributed to myelin by almost twofold relative to zero filtering suggesting that at least half of the unrelated signal has a substantially shorter T1D than myelin. Overall, these results strongly support the sensitivity of ihMT to myelin content.
Validation of ihMT as a myelin sensitive technique by comparison of ihMTR values derived from various RF irradiation preparations with GFP fluorescence intensity, measured in different brain structures. Display omitted
•Inhomogeneous magnetization transfer (ihMT) was validated as a myelin sensitive imaging technique against fluorescence microscopy.•IhMT signal was strongly and significantly correlated with myelin-related plp-GFP (proteolipid - Green Fluorescence Protein) signal.•Short dipolar relaxation time (T1D) filtering is an efficient way to reduce non-myelin contribution in ihMT signal.•MT signal was more weakly correlated with plp-GFP signal and had a much larger non-myelin contribution.•IhMT contrast can be modulated with pulse timing, leading to signals with variable sensitivity and specificity for myelin.
Sprint performance under heat stress: A review Girard, O.; Brocherie, F.; Bishop, D. J.
Scandinavian journal of medicine & science in sports,
June 2015, Letnik:
25, Številka:
S1
Journal Article
Recenzirano
Odprti dostop
Training and competition in major track‐and‐field events, and for many team or racquet sports, often require the completion of maximal sprints in hot (>30 °C) ambient conditions. Enhanced short‐term ...(<30 s) power output or single‐sprint performance, resulting from transient heat exposure (muscle temperature rise), can be attributed to improved muscle contractility. Under heat stress, elevations in skin/core temperatures are associated with increased cardiovascular and metabolic loads in addition to decreasing voluntary muscle activation; there is also compelling evidence to suggest that large performance decrements occur when repeated‐sprint exercise (consisting of brief recovery periods between sprints, usually <60 s) is performed in hot compared with cool conditions. Conversely, poorer intermittent‐sprint performance (recovery periods long enough to allow near complete recovery, usually 60–300 s) in hotter conditions is solely observed when exercise induces marked hyperthermia (core temperature >39 °C). Here we also discuss strategies (heat acclimatization, precooling, hydration strategies) employed by “sprint” athletes to mitigate the negative influence of higher environmental temperatures.
Normobaric hypoxic conditioning (HC) is defined as exposure to systemic and/or local hypoxia at rest (passive) or combined with exercise training (active). HC has been previously used by healthy and ...athletic populations to enhance their physical capacity and improve performance in the lead up to competition. Recently, HC has also been applied acutely (single exposure) and chronically (repeated exposure over several weeks) to overweight and obese populations with the intention of managing and potentially increasing cardio-metabolic health and weight loss. At present, it is unclear what the cardio-metabolic health and weight loss responses of obese populations are in response to passive and active HC. Exploration of potential benefits of exposure to both passive and active HC may provide pivotal findings for improving health and well being in these individuals. A systematic literature search for articles published between 2000 and 2017 was carried out. Studies investigating the effects of normobaric HC as a novel therapeutic approach to elicit improvements in the cardio-metabolic health and weight loss of obese populations were included. Studies investigated passive (
= 7; 5 animals, 2 humans), active (
= 4; all humans) and a combination of passive and active (
= 4; 3 animals, 1 human) HC to an inspired oxygen fraction (Formula: see text) between 4.8 and 15.0%, ranging between a single session and daily sessions per week, lasting from 5 days up to 8 mo. Passive HC led to reduced insulin concentrations (-37 to -22%) in obese animals and increased energy expenditure (+12 to +16%) in obese humans, whereas active HC lead to reductions in body weight (-4 to -2%) in obese animals and humans, and blood pressure (-8 to -3%) in obese humans compared with a matched workload in normoxic conditions. Inconclusive findings, however, exist in determining the impact of acute and chronic HC on markers such as triglycerides, cholesterol levels, and fitness capacity. Importantly, most of the studies that included animal models involved exposure to severe levels of hypoxia (Formula: see text = 5.0%; simulated altitude >10,000 m) that are not suitable for human populations. Overall, normobaric HC demonstrated observable positive findings in relation to insulin and energy expenditure (passive), and body weight and blood pressure (active), which may improve the cardio-metabolic health and body weight management of obese populations. However, further evidence on responses of circulating biomarkers to both passive and active HC in humans is warranted.
Aim
To determine whether repeated maximal‐intensity hypoxic exercise induces larger beneficial adaptations on the hypoxia‐inducible factor‐1α pathway and its target genes than similar normoxic ...exercise, when combined with chronic hypoxic exposure.
Methods
Lowland elite male team‐sport athletes underwent 14 days of passive normobaric hypoxic exposure ≥14 h·day−1 at inspired oxygen fraction (FiO2) 14.5–14.2% with the addition of six maximal‐intensity exercise sessions either in normobaric hypoxia (FiO2 ~14.2%; LHTLH; n = 9) or in normoxia (FiO2 20.9%; LHTL; n = 11). A group living in normoxia with no additional maximal‐intensity exercise (LLTL; n = 10) served as control. Before (Pre), immediately after (Post‐1) and 3 weeks after (Post‐2) the intervention, muscle biopsies were obtained from the vastus lateralis.
Results
Hypoxia‐inducible factor‐1α subunit, vascular endothelial growth factor, myoglobin, peroxisome proliferator‐activated receptor‐gamma coactivator 1‐α and mitochondrial transcription factor A mRNA levels increased at Post‐1 (all P ≤ 0.05) in LHTLH, but not in LHTL or LLTL, and returned near baseline levels at Post‐2. The protein expression of citrate synthase increased in LHTLH (P < 0.001 and P < 0.01 at Post‐1 and Post‐2, respectively) and LLTL (P < 0.01 and P < 0.05 at Post‐1 and Post‐2, respectively), whereas it decreased in LHTL at Post‐1 and Post‐2 (both P < 0.001).
Conclusion
Combined with residence in normobaric hypoxia, repeated maximal‐intensity hypoxic exercise induces short‐term post‐intervention beneficial changes in muscle transcriptional factors that are of larger magnitude (or not observed) than with similar normoxic exercise. The decay of molecular adaptations was relatively fast, with most of benefits already absent 3 weeks post‐intervention.
Blood flow restriction (BFR) is an alternative hypoxic strategy utilizing inflatable cuffs on the legs that limit arterial inflow of blood and mostly occlude venous return. ...the purpose of this ...study was to investigate adaptive responses in RSA and physiology for team-sport players following 3 weeks of RST with BFR compared to unrestricted training. Results: Mean power output during the cycling RSA and anaerobic capacity test improved (p < 0.002) in both BFR (dz = 0.49 and 0.57, respectively) and Non-BFR (dz = 0.86 and 0.83, respectively) groups after training, without between-group differences (p = 0.801 and 0.500, respectively). ...3 weeks of cycling RST did not improve maximal aerobic capacity and maximal quadriceps isometric strength. ...to previous research examining systemic hypoxia, the addition of BFR to RST did not provide further benefits to RSA or physiology potentially due to the brief training duration.
The purpose of this study was to examine the influence of cuff application method during repeated-sprint exercise (RSE) on acute performance, physiological and perceptual responses in Australian ...Rules football players. ...perceived limb discomfort was higher during I-BFRREST (dz = 0.94 and 0.66; respectively) and C-BFR (dz = 1.19 and 0.84; respectively) than Non-BFR and I-BFRWORK Discussion: Similar blood lactate concentration was observed between conditions despite lower mean power output during C-BFR and I-BFRREST than Non-BFR. ...reduced oxygen delivery and phosphocreatine resynthesis with C-BFR and I-BFRREST likely increases peripheral fatigue development and is preferential for athletes who want to obtain a greater metabolic load during RSE for a given mechanical stress. ...C-BFR and I-BFRREST were perceived as more difficult which was driven by greater perceptions of limb discomfort due to increased metabolic stress and discomfort associated with cuff pressure.
We investigated whether perceptually-regulated high-intensity intervals in hypoxia are associated with slower running velocities versus normoxia, when physiological responses and exercise-related ...sensations remain the same. Nineteen trained runners (33.4 ± 9.1 years) completed a high-intensity interval running protocol (4 × 4-min intervals at a clamped perceived rating exertion of 16 on the 6–20 Borg scale, 3-min passive recoveries) in either hypoxic (HYP; FiO2 15.0%) or normoxic (NOR; FiO2 20.9%) conditions. Participants adjusted to a progressively slower running velocity from interval 1–4 (−7.0%), and more so in HYP vs. NOR for intervals 2, 3 and 4 (−4.6%, −6.4% and − 7.9%, respectively; p < .01). Heart rate increased from interval 1–4 (+4.8%; p < .01), independent of condition. Arterial oxygen saturation was lower in HYP vs. NOR (86.0% vs. 94.8%; p < .01). Oxyhemoglobin (−23.7%) and total hemoglobin (−77.0%) decreased, whilst deoxyhemoglobin increased (+44.9%) from interval 1–4 (p < .01), independent of condition. Perceived recovery (−41.6%) and motivation (−21.8%) were progressively lower from interval 1–4, and more so in HYP vs. NOR for intervals 2, 3 and 4 (recovery: −8.8%, −24.2% and − 29.3%; motivation: −5.3%, −20.3% and − 22.4%, respectively; p < .01). Perceived breathlessness (+18.6%), limb discomfort (+44.0%) and pleasure (−32.2%) changed from interval 1–4, with significant differences (+21.8%, +11.3% and − 31.3%, respectively) between HYP and NOR (p < .01). Slower interval running velocities in hypoxia achieve similar heart rate and muscle oxygenation responses to those observed in normoxia when perceptually-regulated, yet at the expense of less favourable exercise-related sensations.
•We investigated psycho-physiological responses to perceptually-regulated high-intensity intervals in hypoxia vs. normoxia.•Runners adjusted to a progressively slower running velocity across intervals, and more so in hypoxia vs. normoxia.•Heart rate and muscle oxygenation values changed across intervals but were matched between environmental conditions.•Exercise-related sensations were negatively impacted across intervals, and more so in hypoxia vs. normoxia.•Overall, a slower external workload in hypoxia achieves a similar internal load than normoxia when perceptually-regulated.•Practitioners should be aware of potential negative carry-over effects following perceptually-regulated exercise in hypoxia.
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