Endurance exercise begun with reduced muscle glycogen stores seems to potentiate skeletal muscle protein abundance and gene expression. However, it is unknown whether this greater signaling responses is due to performing two exercise sessions in close proximity—as a first exercise session is necessary to reduce the muscle glycogen stores. In the present study, we manipulated the recovery duration between a first muscle glycogen‐depleting exercise and a second exercise session, such that the second exercise session started with reduced muscle glycogen in both approaches but was performed either 2 or 15 hours after the first exercise session (so‐called “twice‐a‐day” and “once‐daily” approaches, respectively). We found that exercise twice‐a‐day increased the nuclear abundance of transcription factor EB (TFEB) and nuclear factor of activated T cells (NFAT) and potentiated the transcription of peroxisome proliferator‐activated receptor‐ɣ coactivator 1‐alpha (PGC‐1α), peroxisome proliferator‐activated receptor‐alpha (PPARα), and peroxisome proliferator‐activated receptor beta/delta (PPARβ/δ) genes, in comparison with the once‐daily exercise. These results suggest that part of the elevated molecular signaling reported with previous “train‐low” approaches might be attributed to performing two exercise sessions in close proximity. The twice‐a‐day approach might be an effective strategy to induce adaptations related to mitochondrial biogenesis and fat oxidation.

Caffeine increased total work done above CP, but this was not associated with greater anaerobic work. Rather, this was associated with a higher tolerance to maintain exercise at maximal oxidative metabolic rate.

This study aimed to investigate whether isolated or combined carbohydrate (CHO) and caffeine (CAF) supplementation have beneficial effects on performance during soccer-related tests performed after a previous training session. Eleven male, amateur soccer players completed 4 trials in a randomized, double-blind, and crossover design. In the morning, participants performed the Loughborough Intermittent Shuttle Test (LIST). Then, participants ingested (i) 1.2 g·kg(-1) body mass·h(-1) CHO in a 20% CHO solution immediately after and 1, 2, and 3 h after the LIST; (ii) CAF (6 mg·kg(-1) body mass) 3 h after the LIST; (iii) CHO combined with CAF (CHO+CAF); and (iv) placebo. All drinks were taste-matched and flavourless. After this 4-h recovery, participants performed a countermovement jump (CMJ) test, a Loughborough Soccer Passing Test (LSPT), and a repeated-sprint test. There were no main effects of supplementation for CMJ, LSPT total time, or best sprint and total sprint time from the repeated-sprint test (p>0.05). There were also no main effects of supplementation for heart rate, plasma lactate concentration, rating of perceived exertion (RPE), pleasure-displeasure, and perceived activation (p>0.05). However, there were significant time effects (p<0.05), with heart rate, plasma lactate concentration, RPE, and perceived activation increasing with time, and pleasure-displeasure decreasing with time. In conclusion, isolated and/or combined CHO and CAF supplementation is not able to improve soccer-related performance tests when performed after a previous training session.

Exercise training performed with lowered muscle glycogen stores can amplify adaptations related to oxidative metabolism, but it is not known if this is affected by the “train-low” strategy used (i.e., once-daily versus twice-a-day training). Fifteen healthy men performed 3 wk of an endurance exercise (100-min) followed by a high-intensity interval exercise 2 (twice-a-day group, n = 8) or 14 h (once-daily group, n = 7) later; therefore, the second training session always started with low muscle glycogen in both groups. Mitochondrial efficiency (state 4 respiration) was improved only for the twice-a-day group (group × training interaction, P < 0.05). However, muscle citrate synthase activity, mitochondria, and lipid area in intermyofibrillar and subsarcolemmal regions, and PGC1α, PPARα, and electron transport chain relative protein abundance were not altered with training in either group ( P > 0.05). Markers of aerobic fitness (e.g., peak oxygen uptake) were increased, and plasma lactate, O2 cost, and rating of perceived exertion during a 100-min exercise task were reduced in both groups, although the reduction in rating of perceived exertion was larger in the twice-a-day group (group × time × training interaction, P < 0.05). These findings suggest similar training adaptations with both training low approaches; however, improvements in mitochondrial efficiency and perceived effort seem to be more pronounced with twice-a-day training. NEW & NOTEWORTHY We assessed, for the first time, the differences between two “train-low” strategies (once-daily and twice-a-day) in terms of training-induced molecular, functional, and morphological adaptations. We found that both strategies had similar molecular and morphological adaptations; however, only the twice-a-day strategy increased mitochondrial efficiency and had a superior reduction in the rating of perceived exertion during a constant-load exercise compared with once-daily training. Our findings provide novel insights into skeletal muscle adaptations using the “train-low” strategy.

Acetaminophen has been combined with caffeine for therapeutic purpose, but the effect of co-ingestion of acetaminophen and caffeine on exercise performance has not been investigated. The aim of this study was to determine the effect of isolated and combined ingestion of caffeine and acetaminophen on performance during a 4-km cycling time-trial. In a double-blind, crossover design, eleven men, accustomed to cycling recreationally, completed a 4-km cycling time-trial one hour after the ingestion of cellulose (PLA), acetaminophen (20 mg . kg -1 body mass, ACT), caffeine (5 mg . kg -1 body mass, CAF) or combined acetaminophen and caffeine (20 and 5 mg . kg -1 body mass, respectively, ACTCAF). The perception of pain and rating of perceived exertion were recorded every 1-km, and electromyography and oxygen uptake were continually recorded and averaged each 1-km. Plasma lactate concentration was measured before and immediately after the trial. The time and mean power during the 4-km cycling time-trial was significantly improved (

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27Acetaminophen has been combined with caffeine for therapeutic purpose, but the effect 28 of co-ingestion of acetaminophen and caffeine on exercise performance has not been 29 investigated. The aim of this study was to determine the effect of isolated and combined 30 ingestion of caffeine and acetaminophen on performance during a 4-km cycling time-trial. In a 31 double-blind, crossover design, eleven men, accustomed to cycling recreationally, completed a 32 4-km cycling time-trial one hour after the ingestion of cellulose (PLA), acetaminophen (20 33 mg . kg -1 body mass, ACT), caffeine (5 mg . kg -1 body mass, CAF) or combined acetaminophen 34 and caffeine (20 and 5 mg . kg -1 body mass, respectively, ACTCAF). The perception of pain and 35 rating of perceived exertion were recorded every 1-km, and electromyography and oxygen 36 uptake were continually recorded and averaged each 1-km. Plasma lactate concentration was 37 measured before and immediately after the trial. The time and mean power during the 4-km 38 cycling time-trial was significantly improved (P < 0.05) in CAF (407.9 ± 24.5 s, 241.4 ± 16.1 39 W) compared to PLA (416.1 ± 34.1 s, 234.1 ± 19.2 W) and ACT (416.2 ± 26.6 s, 235.8 ± 19.7 40 W). However, there was no difference between ACTCAF (411.6 ± 27.7 s, 238.7 ± 18.7 W) and 41 the other conditions (P > 0.05). The perception of pain, rating of perceived exertion, 42 electromyography, oxygen uptake, and plasma lactate were similar across the conditions (P > 43 0.05). In conclusion, caffeine but not acetaminophen increases power output ultimately 44 increasing performance during a 4-km cycling time-trial. 45 46 47 48 49 50 51 52 53 3 54 Introduction 55 56During a self-paced, high-intensity cycling time-trial (e.g., 4-km cycling TT), the 57 exercise intensity must be strictly regulated to avoid an exacerbated early accumulation of 58 metabolites that can lead to fatigue [1][2][3]. A disturbance in the intramuscular metabolic milieu 59 (i.e., accumulation of the H + , ADP, AMP and Pi) at the beginning of a high-intensity cycling 60 TT, provoked by increased muscle recruitment (as inferred from electromyography signals, 61 EMG) ultimately increasing power output (PO) [2,3], will activate peripheral sensory nerve 62 terminals [4,5]. These increased afferent signals might result in increased perception of pain 63 [6], leading to a reduction in PO [2,3]. 64 65Acetaminophen (commonly known as paracetamol) has recently been introduced as a 66 potential pharmacological agent to increase exercise performance due to its analgesic 67 proprieties [7-9]. The mechanism by which acetaminophen reliefs pain feelings in humans is 68 not fully known, but it has been attributed to the inhibition of the cyclooxygenase enzymes [10-69 13], potentiation of descending serotoninergic pathways [14,15], and modulation of opioid and 70 cannabinoid CB 1 receptors [11,16]. Although there is not a consensus [17,18], several studies 71 have reported improved performance during high-intensity exercises after a single clinical dose 72(1-1.5 ...

The purpose of this study was to verify the date of birth is a decisive factor for the success of players selected by the coaches to participate in the FIFA U-17 World Cup Emirates 2013. The players' date of birth were classified into four quartiles of three months each (Q1 to Q4). In the qualifying round, 46.5% of the selected players born in Q1, while 12.5% in Q4. This significantly different distribution occurred until the semi-finals. However, in the final match, there were no significant differences between Q1 and Q4. A similar relative age effect also occurred when analyzed only players who actually participated to the matches. Interestingly, despite there was birth date effect on performance in all World Cup stages except in the final, other issues should take into consideration for a team became champion.