Nocturnal Melatonin Ingestion Improves Soccer Players' Short-Term Maximal Performances on the Following Day

Purpose: Exogenous melatonin has been proven to have beneficial effects on sleep. A good sleep quality promotes recovery and improves physical performance. In this sense, the present study aimed to explore the potential effect of nocturnal melatonin ingestion on psycho-cognitive and short-term maximal performances, in the following morning. Method: Twelve professional soccer players (22.9 ± 1.3 years, 1.80 ± 0.05 m, and 72.0 ± 8.8 kg) volunteered to perform two separate testing sessions after either nocturnal melatonin or placebo ingestion. The next morning, participants performed the following psycho-cognitive and physical tests: Hooper's index, reaction time, vigilance, handgrip strength (HG), squat jump (SJ), modified agility T-test (MAT) and Wingate anaerobic test (WanT). Rating of perceived exertion (RPE) and blood lactate [La] were recorded, respectively, immediately and 3 min after the WanT. Blood glucose [GL] was measured before and 3 min after WanT. Results: Compared with placebo, melatonin improved subjective sleep quality, short-term maximal performances (HG and SJ), reaction-time, as well as peak and mean WanT powers and decreased fatigue index and RPE scores. However, [La] and [GL] were not affected by melatonin ingestion. Conclusion: Nocturnal melatonin intake before sleep has beneficial effects on cognitive and physical performances the following day.

Effects of paddles and fins on front crawl kinematics, arm stroke efficiency, coordination, and estimated energy cost

Paddles and fins are used in swimmers training with different objectives (e.g., increase propulsive areas of hands and feet, improve the feeling of water flow). These artificial modifications of the stroke might be viewed as external constraints of the stroke task, both will either disturb or facilitate swimming modalities, so the coaches should manipulate its use to extract benefits for performance. This study seeks to investigate the precise effects of wearing either paddles (PAD) or fins (FINS) vs. a no-equipment (NE) trial in three all-out front crawl exercises on swimmer kinematics, arm stroke efficiency (ηp), upper-limbs coordination patterns (Index of Coordination, IdC), and estimated energy cost (C). Eleven regional to national-level male swimmers participated in the study (age: 25.8 ± 5.5 years, body mass: 75.2 ± 5.5 kg, height: 177 ± 6.5 cm) and were recorded from both sides of the swimming pool to collect all variables. Repeated measures ANOVA and Bonferroni post hoc were used to compare the variables. Effects sizes were calculated. Time to cover the distance and velocity were higher in FINS swimming, with larger values of stroke length (SL) and lower kick amplitude in comparison to the other trials (PAD and NE). The use of FINS also modified the stroke phases durations by presenting significant lower propulsion time during the stroke in comparison to PAD or NE. Values of IdC were lower (IdC < -1%, so catch-up pattern of coordination) for FINS in comparison to NE. In terms of ηp, using PAD or FINS demonstrate higher arm stroke efficiency than swimming without equipment. Finally, C was significantly higher in FINS swimming in comparison to NE and PAD. From the present results, it should be noted that the use of equipment such as fins deeply modify the structure of the swimming stroke (from the performance-related parameters through the kinematics of both upper and lower limbs to the stroke efficiency and coordination pattern). So, using equipment should be appropriately scaled by the coaches to the objectives of the training session in swimming, and in emergent sports such as "SwimRun", paddles and fins must be viewed as tools to achieve higher velocities to cover a given distance.

Cold water immersion after a soccer match: Does the placebo effect occur?

Although cold water immersion (CWI) is one of the most widely used post-exercise strategies to accelerate recovery processes, the benefits of CWI may be associated with placebo effects. This study aimed to compare the effects of CWI and placebo interventions on time course of recovery after the Loughborough Intermittent Shuttle Test (LIST). In a randomized, counterbalanced, crossover study, twelve semi-professional soccer players (age 21.1 ± 2.2 years, body mass 72.4 ± 5.9 kg, height 174.9 ± 4.6 cm, V ˙ O_2max 56.1 ± 2.3 mL/min/kg) completed the LIST followed by CWI (15 min at 11°C), placebo (recovery Pla beverage), and passive recovery (Rest) over three different weeks. Creatine kinase (CK), C-reactive protein (CRP), uric acid (UA), delayed onset muscle soreness (DOMS), squat jump (SJ), countermovement jump (CMJ), 10-m sprint (10 mS), 20-m sprint (20 mS) and repeated sprint ability (RSA) were assessed at baseline and 24 and 48 h after the LIST. Compared to baseline, CK concentration was higher at 24 h in all conditions (p < 0.01), while CRP was higher at 24 h only in CWI and Rest conditions (p < 0.01). UA was higher for Rest condition at 24 and 48 h compared to Pla and CWI conditions (p < 0.001). DOMS score was higher for Rest condition at 24 h compared to CWI and Pla conditions (p = 0.001), and only to Pla condition at 48 h (p = 0.017). SJ and CMJ performances decreased significantly after the LIST in Rest condition (24 h: -7.24%, p = 0.001 and -5.45%, p = 0.003 respectively; 48 h: -9.19%, p < 0.001 and -5.70% p = 0.002 respectively) but not in CWI and Pla conditions. 10 mS and RSA performance were lower for Pla at 24 h compared to CWI and Rest conditions (p < 0.05), while no significant change was observed for 20 mS time. These data suggests that CWI and Pla intervention were more effective than the Rest conditions in recovery kinetics of muscle damage markers and physical performance. Furthermore, the effectiveness of CWI would be explained, at least in part, by the placebo effect.

Exponential Relationship Between Maximal Apnea Duration and Exercise Intensity in Non-apnea Trained Individuals

It is well known that the duration of apnea is longer in static than in dynamic conditions, but the impact of exercise intensity on the apnea duration needs to be investigated. The aim of this study was to determine the relationship between apnea duration and exercise intensity, and the associated metabolic parameters. Ten healthy active young non-apnea trained (NAT) men participated in this study. During the first visit, they carried out a maximum static apnea (SA) and a maximal progressive cycle exercise to evaluate the power output achieved at peak oxygen uptake (PVO₂peak). During the second visit, they performed four randomized dynamic apneas (DAs) at 20, 30, 40, and 50% of PVO₂peak (P20, P30, P40, and P50) preceded by 4 min of exercise without apnea. Duration of apnea, heart rate (HR), arterial oxygen saturation (SpO₂), blood lactate concentration [La], rating of perceived exertion (RPE), and subjective feeling were recorded. Apnea duration was significantly higher during SA (68.1 ± 23.6 s) compared with DA. Apnea duration at P20 (35.6 ± 11.7 s) was higher compared with P30 (25.6 ± 6.3 s), P40 (19.2 ± 6.7 s), and P50 (16.9 ± 2.5 s). The relationship between apnea duration and exercise intensity followed an exponential function (y = 56.388e^{-0.025 x} ). SA as DA performed at P20 and P30 induces a bradycardia. Apnea induces an SpO₂ decrease which is higher during DA (-10%) compared with SA (-4.4%). The decreases of SPO₂ recorded during DA do not differ despite the increase in exercise intensity. An increase of [La] was observed in P30 and P40 conditions. RPE and subjective feeling remained unchanged whatever the apnea conditions might be. These results suggest that the DA performed at 30% of VO₂peak could be the best compromise between apnea duration and exercise intensity. Then, DA training at low intensity could be added to aerobic training since, despite the moderate hypoxia, it is sufficient to induce and increase [La] generally observed during high-intensity training.

Effects of Extended Underwater Sections on the Physiological and Biomechanical Parameters of Competitive Swimmers

Despite changes in the underwater sections of swimming races affecting overall performance, there is no information about the effects of the apnea-induced changes on the physiological state of competitive swimmers. The aim of the present research was to examine the effect of changes in the underwater race sections on the physiological [blood lactate concentration, heart rate, and rating of perceived exertion (RPE)] and biomechanical (underwater time, distance, and velocity) parameters of competitive swimmers. Twelve youth competitive swimmers belonging to the national team (706 ± 28.9 FINA points) performed 2 × 75 m efforts under three different conditions, while maintaining a 200 m race pace: (1) free underwater sections, (2) kick number of condition 1 plus two kicks, and (3) maximum distance underwater. Overall performance was maintained, and underwater section durations increased from condition 1 to 3 as expected according to the experimental design. Heart rate and blood lactate concentration values did not show differences between conditions, but the RPE values were significantly greater (F_{2, 36} = 18.00, p = 0.001, η²: 0.50) for the constrained (conditions 2 and 3) vs. the free underwater condition. Underwater parameters were modified within the 75 m efforts (lap 1 to lap 3), but the magnitude of changes did not depend on the experimental condition (all lap × condition effects p > 0.05). Controlled increases of underwater sections in trained swimmers can led to optimizing performance in these race segments despite small increases of perceived discomfort.

Underwater and Surface Swimming Parameters Reflect Performance Level in Elite Swimmers

Although the role of underwater phases is well-known, no study has taken an interest in describing and quantifying the distance and time spent in apnea as a condition for optimal performance. This study aimed to investigate the impact of time and distance spent underwater and surface parameters on the swimming performance of elite swimmers. The performances of 79 swimmers in 100-m freestyle were analyzed (short-course). The underwater and spatiotemporal parameters of three groups have been recorded: finalists of the 2018 World Swimming Championships (WORLD), French swimmers who reached a 100 m performance time under 50 s at the 2018 French National Championships (UND50), and those who reached a 100 m performance time above 50 s (UP50). The WORLD group spent more distance underwater (37.50 ± 4.92 m) in comparison with UND50 (31.90 ± 4.88 m, p < 0.05) and UP50 (31.94 ± 4.93 m, p < 0.01) groups. The total percentage of non-swimming time was higher for WORLD (39.11 ± 4.73%) vs. UND50 (34.21 ± 4.55%, p < 0.05) and UP50 (33.94 ± 5.00%, p < 0.01). In addition, underwater speed was higher for WORLD (2.54 ± 0.05 m/s) compared with UND50 (2.46 ± 0.09 m/s, p < 0.05) and UP50 (2.38 ± 0.11 m/s, p < 0.01). Three parameters among the underwater phases (i.e. distance underwater, speed underwater, and total percentage of non-swimming time) determine the 100-m freestyle short course performance. These data suggest an appropriate focus on specific apnea training to improve underwater skills during short-course swimming performances.

Effect of swim intensity on responses to dynamic apnoea

The aim of this study was to determine the influence of swim intensity on acute responses to dynamic apnoea. 9 swimmers performed one 50 m front crawl trial in four different conditions: at 400 m velocity (V₄₀₀) with normal breathing (NB), at V₄₀₀ in complete apnoea (Ap), at maximal velocity (V_max) with NB and at V_max in Ap. Peak heart rate (HR_peak), blood lactate concentration after exercise (Lac_{post ex}) and Borg rating of perceived exertion (RPE) were measured. Arterial oxygen saturation (SpO₂) was monitored with a pulse oximeter at forehead level during and after exercise. In Ap, swimming at V₄₀₀ induced a significantly lower HR_peak and Lac_{post ex} than swimming at V_max whilst RPE and the kinetics of SpO₂ were not different at V₄₀₀ and at V_max. The minimal value of SpO₂ in Ap was reached 10 to 11 s after the end of V₄₀₀ and V_max (81.7 ± 10.1% and 84.4 ± 10.6%, respectively). Swimming a 50 m front crawl in Ap resulted in a large decrease in SpO₂ which occurred only after the cessation of exercise. The higher duration of apnoea during submaximal exercise could explain why SpO₂ and RPE reached the same values as for maximal exercise.​.

Physiological Dynamic Apnea Responses in Relation to Apnea Capacity in Triathletes

The aim was to assess the cardiac, arterial oxygen saturation, lactate, hormonal and Borg rating of perceived exertion (RPE) responses to acute apnea in relation to apnea capacity in 18 middle-aged triathletes. Subjects were monitored while swimming two 50-m freestyle exercise trials with fins at maximal speed: with normal frequency breathing (NB) and with complete apnea (Ap); the latter was used to assess apnea capacity. The subjects with significant alteration in swimming performance inducing a time increase greater than 2.5% during Ap vs. NB were put in the group: bad apnea capacity (Bad Ap); the others, who showed no significant alteration in performance, were put in the group: Good Ap. Under apnea, both groups showed a decrease in arterial oxygen saturation (p<0.05). In Ap conditions, only Bad Ap had a significant lower maximal heart rate vs. NB (p<0.05), with lower blood lactate (p<0.05) and arm stroke frequency (p<0.01). No change in saliva hormonal concentrations was found during the experiment for both groups, whereas RPE responses were increased in the Good Ap group under Ap vs. NB conditions. In conclusion, a good apnea capacity seems to be associated with lower cardiovascular and metabolic apnea alterations in middle-aged recreationally-trained triathletes.

Acute apnea swimming: metabolic responses and performance

Competitive swimmers regularly perform apnea series with or without fins as part of their training, but the ergogenic and metabolic repercussions of acute and chronic apnea have not been examined. Therefore, we aimed to investigate the cardiovascular, lactate, arterial oxygen saturation and hormonal responses to acute apnea in relation to performance in male swimmers. According to a randomized protocol, 15 national or regional competitive swimmers were monitored while performing four 100-m freestyle trials, each consisting of four 25-m segments with departure every 30 seconds at maximal speed in the following conditions: with normal frequency breathing with fins (F) and without fins (S) and with complete apnea for the four 25-m segments with (FAp) and without fins (SAp). Heart rate (HR) was measured continuously and arterial oxygen saturation, blood, and saliva samples were assessed after 30 seconds, 3 minutes, and 10 minutes of recovery, respectively. Swimming performance was better with fins than without both with normal frequency breathing and apnea (p < 0.001). Apnea induced no change in lactatemia, but a decrease in arterial oxygen saturation in both SAp and FAp (p < 0.001) was noted and a decrease in HR and swimming performance in SAp (p < 0.01). During apnea without fins, performance alteration was correlated with bradycardia (r = 0.63) and arterial oxygen desaturation (r = -0.57). Saliva dehydroepiandrosterone was increased compared with basal values whatever the trial (p ≤ 0.05), whereas no change was found in saliva cortisol or testosterone. Further studies are necessary to clarify the fin effect on HR and performance during apnea swimming.