Variability of external load measures during soccer match play: Influence of player fitness or pacing?

Purpose: The aims of this study were to examine the variability of selected external load metrics within 15-min intervals during soccer match play and examine their relationship with players’ high-intensity intermittent fitness. Methods: A total of 18 male soccer players were monitored for their external load metrics during 26 matches which included: total distance (TD), high metabolic load distance (HMLD), and mechanical work (MW) (defined as the sum of accelerations and decelerations >3 m2). Additionally, players completed the 30-15 Intermittent Fitness Test (VIFT). Results: TD had lower coefficient of variation (CV) values than HMLD and MW (ES; 5.2 to 6.4; very large). Within-players’ ∆-15min showed moderate-to-large decreases (ES; -0.7 to -1.6) and increases (ES; 0.9 to 1.8) in absolute and CV values, respectively. Large relationships (r= 0.55 to 0.61) were observed between VIFT and 15-minmean and 15-minbest in all selected external load metrics. However, small-to-moderate (0.27 to 0.41) associations were observed between VIFT and ∆-15min in selected external load metrics. Conclusion: These findings suggest that those players with relatively lower intermittent running capacity might show lower variability during the match, as evidenced by smaller reductions in high intensity actions during the final 15 minutes. We attribute these observations to players’ possessing better pacing strategies

Short Duration Small Sided Football and to a Lesser Extent Whole Body Vibration Exercise Induce Acute Changes in Markers of Bone Turnover.

We aimed to study whether short-duration vibration exercise or football sessions of two different durations acutely changed plasma markers of bone turnover and muscle strain. Inactive premenopausal women (n = 56) were randomized to complete a single bout of short (FG15) or long duration (FG60) small sided football or low magnitude whole body vibration training (VIB). Procollagen type 1 amino-terminal propeptide (P1NP) was increased during exercise for FG15 (51.6 ± 23.0 to 56.5 ± 22.5 μg·L-1, mean ± SD, P 0.05). An increase in osteocalcin was observed 48 h after exercise (P < 0.05), which did not differ between exercise groups. C-terminal telopeptide of type 1 collagen was not affected by exercise. Blood lactate concentration increased during exercise for FG15 (0.6 ± 0.2 to 3.4 ± 1.2 mM) and FG60 (0.6 ± 0.2 to 3.3 ± 2.0 mM), but not for VIB (0.6 ± 0.2 to 0.8 ± 0.4 mM) (P < 0.05). Plasma creatine kinase increased by 55 ± 63% and 137 ± 119% 48 h after FG15 and FG60 (P < 0.05), but not after VIB (26 ± 54%, NS). In contrast to the minor elevation in osteocalcin in response to a single session of vibration exercise, both short and longer durations of small sided football acutely increased plasma P1NP, osteocalcin, and creatine kinase. This may contribute to favorable effects of chronic training on musculoskeletal health

Improved Exercise Tolerance with Caffeine Is Associated with Modulation of both Peripheral and Central Neural Processes in Human Participants

BackgroundCaffeine has been shown to enhance exercise performance and capacity. The mechanisms remain unclear but are suggested to relate to adenosine receptor antagonism, resulting in increased central motor drive, reduced perception of effort, and altered peripheral processes such as enhanced calcium handling and extracellular potassium regulation. Our aims were to investigate how caffeine (i) affects knee extensor PCr kinetics and pH during repeated sets of single-leg knee extensor exercise to task failure and (ii) modulates the interplay between central and peripheral neural processes. We hypothesized that the caffeine-induced extension of exercise capacity during repeated sets of exercise would occur despite greater disturbance of the muscle milieu due to enhanced peripheral and corticospinal excitatory output, central motor drive, and muscle contractility.MethodsNine healthy active young men performed five sets of intense single-leg knee extensor exercise to task failure on four separate occasions: for two visits (6 mg·kg−1 caffeine vs placebo), quadriceps 31P-magnetic resonance spectroscopy scans were performed to quantify phosphocreatine kinetics and pH, and for the remaining two visits (6 mg·kg−1 caffeine vs placebo), femoral nerve electrical and transcranial magnetic stimulation of the quadriceps cortical motor area were applied pre- and post exercise.ResultsThe total exercise time was 17.9 ± 6.0% longer in the caffeine (1,225 ± 86 s) than in the placebo trial (1,049 ± 73 s, p = 0.016), and muscle phosphocreatine concentration and pH (p &lt; 0.05) were significantly lower in the latter sets of exercise after caffeine ingestion. Voluntary activation (VA) (peripheral, p = 0.007; but not supraspinal, p = 0.074), motor-evoked potential (MEP) amplitude (p = 0.007), and contractility (contraction time, p = 0.009; and relaxation rate, p = 0.003) were significantly higher after caffeine consumption, but at task failure MEP amplitude and VA were not different from placebo. Caffeine prevented the reduction in M-wave amplitude that occurred at task failure (p = 0.039).ConclusionCaffeine supplementation improved high-intensity exercise tolerance despite greater-end exercise knee extensor phosphocreatine depletion and H+ accumulation. Caffeine-induced increases in central motor drive and corticospinal excitability were attenuated at task failure. This may have been induced by the afferent feedback of the greater disturbance of the muscle milieu, resulting in a stronger inhibitory input to the spinal and supraspinal motor neurons. However, causality needs to be established through further experiments

The effect of two consecutive soccer games on muscle damage and performance markers

High‐intensity activities during a soccer game, such as sprints, accelerations, change of direction, jumps, shoot, requires high force through the Stretch – Shortening Cycle (SSC), which is associated with the exercise – induced muscle damage. Consequences of muscle damage are muscle soreness and loss of muscle power. The aim of this study was to investigate the effect of two consecutive soccer games on indices of exercise – induced muscle damage (EIMD) and physical performance (PP). In this study participated 10 soccer players (age: 20.7years, height: 177cm, weight: 73kg, body fat: 6.4%, VO2max 55 ml/kg/min) who joined the first week of experimental design without playing in matches. The second week included two soccer games which had 90 minutes duration and separated 72 hours. Measurements executed daily in the morning during first and second week up to 48 hours after the second soccer game. The EIMD determined through thigh circumferences, knee joint of range motion (KJRM) and delayed onset of muscle damage (DOMS). The PP determined through squat jump (SJ) and countermovement jump (CJ). Data was analyzed with ANOVA repeated measures. Results show that thigh circumferences were significantly different 48 hours after the first and second game, and DOMS was higher 24 and 48 hours after second game. PP deteriorated in both SJ and CJ which is ranged between 10‐20% with the greatest decrement 48 hours after the soccer games. In conclusion, the two soccer games caused noticeable changes in the EIMD and PP indices. Coaches should plan suitable training sessions after games taking account of enough recovery period for the players

Improved Exercise Tolerance with Caffeine Is Associated with Modulation of both Peripheral and Central Neural Processes in Human Participants

This is the author accepted manuscript. The final version is available from Frontiers Media via the DOI in this record.Background: Caffeine has been shown to enhance exercise performance and capacity. The mechanisms remain unclear but are suggested to relate to adenosine receptor antagonism, resulting in increased central motor drive, reduced perception of effort, and altered peripheral processes such as enhanced calcium handling and extracellular potassium regulation. Our aims were to investigate how caffeine (i) affects knee extensor PCr kinetics and pH during repeated sets of single-leg knee extensor exercise to task failure and (ii) modulates the interplay between central and peripheral neural processes. We hypothesized that the caffeine-induced extension of exercise capacity during repeated sets of exercise would occur despite greater disturbance of the muscle milieu due to enhanced peripheral and corticospinal excitatory output, central motor drive, and muscle contractility. Methods: Nine healthy active young men performed five sets of intense single-leg knee extensor exercise to task failure on four separate occasions: for two visits (6 mg·kg−1 caffeine vs placebo), quadriceps 31P-magnetic resonance spectroscopy scans were performed to quantify phosphocreatine kinetics and pH, and for the remaining two visits (6 mg·kg−1 caffeine vs placebo), femoral nerve electrical and transcranial magnetic stimulation of the quadriceps cortical motor area were applied pre- and post exercise. Results: The total exercise time was 17.9 ± 6.0% longer in the caffeine (1,225 ± 86 s) than in the placebo trial (1,049 ± 73 s, p = 0.016), and muscle phosphocreatine concentration and pH (p < 0.05) were significantly lower in the latter sets of exercise after caffeine ingestion. Voluntary activation (VA) (peripheral, p = 0.007; but not supraspinal, p = 0.074), motor-evoked potential (MEP) amplitude (p = 0.007), and contractility (contraction time, p = 0.009; and relaxation rate, p = 0.003) were significantly higher after caffeine consumption, but at task failure MEP amplitude and VA were not different from placebo. Caffeine prevented the reduction in M-wave amplitude that occurred at task failure (p = 0.039). Conclusion: Caffeine supplementation improved high-intensity exercise tolerance despite greater-end exercise knee extensor phosphocreatine depletion and H+ accumulation. Caffeine-induced increases in central motor drive and corticospinal excitability were attenuated at task failure. This may have been induced by the afferent feedback of the greater disturbance of the muscle milieu, resulting in a stronger inhibitory input to the spinal and supraspinal motor neurons. However, causality needs to be established through further experiments.No funding was associated with this work, but JF’s salary is supported by NIHR

Short-term high-intensity interval exercise training attenuates oxidative stress responses and improves antioxidant status in healthy humans

This study investigated the changes in oxidative stress biomarkers and antioxidant status indices caused by a 3-week high-intensity interval training (HIT) regimen. Eight physically active males performed three HIT sessions/week over 3. weeks. Each session included four to six 30-s bouts of high-intensity cycling separated by 4. min of recovery. Before training, acute exercise elevated protein carbonyls (PC), thiobarbituric acid reactive substances (TBARS), glutathione peroxidase (GPX) activity, total antioxidant capacity (TAC) and creatine kinase (CK), which peaked 24. h post-exercise (252 ± 30%, 135 ± 17%, 10 ± 2%, 85 ± 14% and 36 ± 13%, above baseline, respectively; p&lt;. 0.01), while catalase activity (CAT) peaked 30. min post-exercise (56 ± 18% above baseline; p&lt;. 0.01). Training attenuated the exercise-induced increase in oxidative stress markers (PC by 13.3 ± 3.7%; TBARS by 7.2 ± 2.7%, p&lt;. 0.01) and CK activity, despite the fact that total work done was 10.9 ± 3.6% greater in the post- compared with the pre-training exercise test. Training also induced a marked elevation of antioxidant status indices (TAC by 38.4 ± 7.2%; CAT by 26.2 ± 10.1%; GPX by 3.0 ± 0.6%, p&lt;. 0.01). Short-term HIT attenuates oxidative stress and up-regulates antioxidant activity after only nine training sessions totaling 22. min of high intensity exercise, further supporting its positive effect not only on physical conditioning but also on health promotion. © 2013 Elsevier Ltd

A MICROCYCLE OF INFLAMMATION FOLLOWING A TEAM HANDBALL GAME

Chatzinikolaou, A, Christoforidis, C, Avloniti, A, Draganidis, D, Jamurtas, AZ, Stampoulis, T, Ermidis, G, Sovatzidis, A, Papassotiriou, I, Kambas, A, and Fatouros, IG. A microcycle of inflammation following a team handball game. J Strength Cond Res 28(7): 1981-1994, 2014-This study investigated the timecourse of performance and inflammatory responses during a simulated 6-day in-season microcycle following a team handball (TH) game. Twenty-four handball players participated in a 1-week control trial and in an experimental trial (TH game participation followed by a 6-day training microcycle). Concentrations of lactate, glucose, glycerol, triglycerides, nonesterified fatty acids (NEFAs), and ammonia were measured pregame and postgame. Heart rate (HR) was monitored during the game. Performance (jumping, speed, agility, line-drill testing, and strength), muscle damage (knee range of motion [ROM], knee extensors/flexors delayed onset muscle soreness [DOMS], and creatine kinase activity [CO, inflammatory (leukocyte count, C-reactive protein, interleukins 13 and 6 [IL-beta and IL-6], soluble vascular adhesion molecule 1 [sVCAM-11, p-selectin, uric acid, cortisol, and testosterone), and oxidative stress (malondialdehyde [MDA], protein carbonyls [PC], reduced [GSH] and oxidized glutathione [GSSG], total antioxidant capacity (TAC), catalase, glutathione peroxidase activity [GPX]) markers were determined pregame, postgame, and daily for 6 consecutive days postgame. The game induced a marked rise of HR (similar to 170 b.min(-1)), lactate (similar to 8-fold), glycerol (60%), NEFA (105%), and ammonia (similar to 62%). Performance deteriorated until 24 hours postgame. Knee ROM decreased (3-5%), whereas DOMS and CK increased (3- to 5-fold and 80-100%, respectively) 24 hours postgame. Leukocyte count, IL-13, IL-6, cortisol, MDA, PC, and catalase increased only immediately postgame. C-reactive protein and uric acid increased at 24 hours; sVCAM-1, GSSG, and GPX peaked postgame and remained elevated for 24 hours. The GSH declined until 24 hours postgame. Results suggest that a TH game represents a strong metabolic challenge and induces a short-lived and modest inflammatory response that may affect performance for as long as 24 hours postgame

Skeletal muscle phenotype and game performance in elite women football players

We combined game activity analyses with skeletal muscle phenotypes and comprehensive physiological testing to elucidate factors of importance for physical performance in elite women's football. GPS-data from an experimental game, sprint and endurance testing, and muscle tissue analysis of metabolic enzyme activity, protein expression and fiber type composition were completed for international top-level women players (n = 20; age; 23 ± 4 yrs, height; 166 ± 10 cm, weight; 60 ± 8 kg; VO2max; 51 ± 6 ml/min/kg). Muscle monocarboxylate transporter 4 (MCT4) protein expression explained 46% of the variance in total game distance, while the ability to maintain high-intensity running (HIR) during the final 15 min of the game correlated to myosin heavy chain 1 (MHCI) and Na+-K+ ATPase β1, FXYD1 (phospholemman) and superoxide dismutase 2 (SOD2) protein expression (range: r = 0.51–0.71; all p &lt; 0.05). Total HIR distance correlated with (MHCIIa) protein expression (r = 0.51; p &lt; 0.05), while muscle Na+/H+ exchanger 1 (NHE1) protein explained 36% of the variance in game sprint distance (p &lt; 0.05). Total game accelerations (actions &gt;4 m/s2) correlated with platelet endothelial cell adhesion molecule (PECAM-1) protein expression (r = 0.51; p &lt; 0.05), while concentric knee flexor strength explained 42–62% of the variance in intense decelerations (&gt;4 m/s2). In conclusion, for elite women players’ game endurance performance and resistance to end-game fatigue were affected by monocarboxylate transporter expression and myosin heavy chain profile. HIR was also correlated to ion transporter expression and muscle antioxidative capacity. Finally, the importance of functional strength and measures of muscle vascularization in relation to total game decelerations and accelerations, respectively, illustrates the complex physiological demands in elite women's football. © 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd