Resistance training presents beneficial effects on bone development of adolescents engaged in swimming but not in impact sports: ABCD Growth Study.

BACKGROUND: Sports practice during adolescence is important to enhance bone development, although it may provide different effects depending on the mechanical impact present in the sport. Besides, resistance training (RT) may also induce bone changes directly (via muscle contractions) and indirectly (via myokines). However, there have been no studies analyzing the longitudinal influence of engaging in sport with and without added mechanical load. Thus, this study aims to analyze the combined effects of sports participation and resistance training on areal bone mineral density (aBMD) accrual in adolescent athletes participating in swimming and impact sports for 12-months. METHODS: This was a 12-month longitudinal study. The sample comprised 91 adolescents (21 females) aged 10 to 18 years, engaged in impact sports (basketball, tennis, track & field, baseball and gymnastics, n = 66) and non-impact sport (swimming, n = 25). The sample was divided according to resistance training participation: impact sports only (n = 45), impact sports + resistance training (n = 21), swimming-only (n = 17) and swimming + resistance training (n = 8). aBMD and soft tissues were measured using dual-energy X-ray absorptiometry. Generalized linear models analysis was used for the resistance training (RT) x type of sport interaction in predicting aBMD changes overtime, adjusting for maturation, sex and baseline aBMD. RESULTS: After 12-months, all groups showed a significant increase in aBMD, except for the swimming groups (regardless of resistant training), which showed a significant loss in spine aBMD (-0.045 [-0.085 to -0.004] g/cm2 in swimming-only and - 0.047 [-0.073 to -0.021] g/cm2 in swimming + RT). In comparisons between groups, only swimming + RT group, compared with swimming-only group presented higher upper limbs aBMD (0.096 g/cm2 [0.074 to 0.118] in swimming + RT vs. 0.046 [0.032 to 0.060] g/cm2 in swimming only; p < 0.05) and whole body less head (WBLH) aBMD (0.039 [0.024 to 0.054] g/cm2 in swimming + RT vs. 0.017 [0.007 to 0.027] g/cm2 swimming-only; p < 0.05). CONCLUSION: Despite the significant gain in aBMD in all groups and body sites after 12-months, except for the spine site of swimmers, the results indicate that participation in RT seems to improve aBMD accrual in swimmers at the upper limbs and WBLH.

Dimensionality of locomotor behaviors in developing C. elegans.

Adult animals display robust locomotion, yet the timeline and mechanisms of how juvenile animals acquire coordinated movements and how these movements evolve during development are not well understood. Recent advances in quantitative behavioral analyses have paved the way for investigating complex natural behaviors like locomotion. In this study, we tracked the swimming and crawling behaviors of the nematode Caenorhabditis elegans from postembryonic development through to adulthood. Our principal component analyses revealed that adult C. elegans swimming is low dimensional, suggesting that a small number of distinct postures, or eigenworms, account for most of the variance in the body shapes that constitute swimming behavior. Additionally, we found that crawling behavior in adult C. elegans is similarly low dimensional, corroborating previous studies. Further, our analysis revealed that swimming and crawling are distinguishable within the eigenworm space. Remarkably, young L1 larvae are capable of producing the postural shapes for swimming and crawling seen in adults, despite frequent instances of uncoordinated body movements. In contrast, late L1 larvae exhibit robust coordination of locomotion, while many neurons crucial for adult locomotion are still under development. In conclusion, this study establishes a comprehensive quantitative behavioral framework for understanding the neural basis of locomotor development, including distinct gaits such as swimming and crawling in C. elegans.

Inspiratory muscles pre-activation in young swimmers submitted to a tethered swimming test: effects on mechanical, physiological, and skin temperature parameters.

Inspiratory muscles pre-activation (IMPA) has been studied to improve subsequent performance in swimming. However, the effects of IMPA on various parameters in swimmers are still unknown. Therefore, this study aimed to investigate the effects of IMPA on the mechanical parameters, physiological responses, and their possible correlations with swimming performance. A total of 14 young swimmers (aged 16 ± 0 years) underwent a 30-s all-out tethered swimming test, preceded or not by IMPA, a load of 40% of the maximal inspiratory pressure (MIP), and with a volume of 2 sets of 15 repetitions. The mechanical (strength, impulse, and fatigue index) and physiological parameters (skin temperature and lactatemia) and the assessment of perceived exertion and dyspnea were monitored in both protocols. The IMPA used did not increase the swimming force, and skin temperature, decrease blood lactate concentration, or subjective perception of exertion and dyspnea after the high-intensity tethered swimming exercises. Positive correlations were found between mean force and blood lactate (without IMPA: r = 0.62, P = 0.02; with IMPA: r = 0.65, P = 0.01). The impulse was positively correlated with blood lactate (without IMPA: r = 0.71, P < 0.01; with IMPA: r = 0.56, P = 0.03). Our results suggest that new IMPA protocols, possibly with increased volume, should be developed in order to improve the performance of young swimmers.

A Single Dose of Beetroot Juice not Enhance Performance during Intervallic Swimming Efforts.

Despite the numerous scientific evidence on the topic, there is no clear and consistent answer that clarifies the true effects of beetroot juice (BJ) supplementation on different types of physical performance. This study examined whether an acute intake of BJ improves swimming performance, physiological variables of anaerobic metabolism, or subjective measures during high-intensity interval exercise with incomplete rest in competitive swimmers. Eighteen competitive swimmers (nine females and nine males) participated in this cross-over randomized, placebo-controlled, double-blind and counterbalanced study. In two trials, swimmers ingested BJ (70 mL, 6.4 mmol/400 mg NO3-) or placebo (PLA) (70 mL, 0.04 mmol/3 mg NO3-) three hours before a 2×6×100 m maximal effort with 40 seconds rest between repetitions and three minutes between blocks. The 100 m times showed no differences between groups (p > 0.05), but there was an interaction between block×repetition×condition (F5 = 3.10; p = 0.046; ηp2 = 0.54), indicating that the BJ group decreased the time of the sixth repetition of block2 compared to block1 (p = 0.01). Lactate concentration showed no differences between conditions (p > 0.05), but there was a main effect of block (ηp2 = 0.60) and a block×repetition interaction (ηp2 = 0.70), indicating higher values in block2 and increasing values between repetitions in block1. The subjective scales, perception of exertion (RPE) and Total Quality Recovery (TQR), showed no effects of condition (p > 0.05), but BJ swimmers had a greater TQR in the last repetitions of each block. In conclusion, a single dose of BJ did not enhance intermittent swimming performance or modified the physiological (lactate and heart rate) or subjective (RPE and TQR) variables; although there was a possible positive effect on the exercise tolerance at the end of effort.

Benefits and limitations of isokinetic force assessments in swimmer's shoulders: A systematic review.

OBJECTIVE: To indicate the benefits and limitations of the isokinetic test results for the performance of the main shoulder joint movements in swimmers, considering the different competitive levels, swimming techniques, race distances, and sex. METHODS: Search on the PubMed, CENTRAL, Medline, LILACS, and SCOPUS databases for the oldest records up to October 2022. Risk of bias, methodological quality, and level of evidence were evaluated based on the NHLBI checklist. RESULTS: 29 articles met the criteria and were included in this study. The quality analysis classified three as "good" and 26 as "regular", with a KAPPA index of 0.87. The main benefits found involved assessments of the clinical condition of the shoulder joint complex, relationships with performance, and reliability studies. The limitations found point to the participant's positioning in the instrument, use of angular velocity above 180°/s, and sample size. CONCLUSION: The use of the isokinetic dynamometer allows verifying the levels of strength, endurance, balance, and asymmetries among swimmers of different techniques, distances, competitive levels, and sex. Thus, it helps in the analysis and monitoring of the clinical conditions of swimmers' shoulder joints, contributing to the decision-making process of physiotherapists and coaches.

Variation vs. specialization: the dose-time-effect of technical and physiological variety in the development of elite swimmers.

OBJECTIVE: It is heavily discussed whether larger variety or specialization benefit elite performance at peak age. Therefore, this study aimed to determine technical (number of different swimming strokes) and physiological (number of different race distances) variety required to become an international-class swimmer (> 750 swimming points) based on 1'522'803 race results. RESULTS: Correlation analyses showed lower technical variety in higher ranked swimmers (P < 0.001), yet with small effects (0.11-0.30). However, Poisson distribution revealed dose-time-effects and specified number of swimming strokes required during each age group. Specifically, freestyle swimmers showed highest chances when starting to compete in three to four swimming strokes but reduced their variety to three swimming strokes at the ages of 12/13yrs with another transition to two swimming strokes at the ages of 19/21yrs (female/male swimmers, respectively). Although both sexes showed similar specialization pattern throughout their career, earlier specialization was generally evident in female compared to male swimmers. At peak performance age, freestyle was most frequently combined with butterfly. Swimmers who either kept competing in all five swimming strokes or focused on only one at the beginning of their careers showed lowest probability of becoming an international-class swimmer. Physiological variety increased during junior age but declined again to three race distances towards elite age.

Electromechanical enhancement of live jellyfish for ocean exploration.

The vast majority of the ocean's volume remains unexplored, in part because of limitations on the vertical range and measurement duration of existing robotic platforms. In light of the accelerating rate of climate change impacts on the physics and biogeochemistry of the ocean, the need for new tools that can measure more of the ocean on faster timescales is becoming pressing. Robotic platforms inspired or enabled by aquatic organisms have the potential to augment conventional technologies for ocean exploration. Recent work demonstrated the feasibility of directly stimulating the muscle tissue of live jellyfish via implanted microelectronics. We present a biohybrid robotic jellyfish that leverages this external electrical swimming control, while also using a 3D printed passive mechanical attachment to streamline the jellyfish shape, increase swimming performance, and significantly enhance payload capacity. A six-meter-tall, 13 600 l saltwater facility was constructed to enable testing of the vertical swimming capabilities of the biohybrid robotic jellyfish over distances exceeding 35 body diameters. We found that the combination of external swimming control and the addition of the mechanical forebody resulted in an increase in swimming speeds to 4.5 times natural jellyfish locomotion. Moreover, the biohybrid jellyfish were capable of carrying a payload volume up to 105% of the jellyfish body volume. The added payload decreased the intracycle acceleration of the biohybrid robots relative to natural jellyfish, which could also facilitate more precise measurements by onboard sensors that depend on consistent platform motion. While many robotic exploration tools are limited by cost, energy expenditure, and varying oceanic environmental conditions, this platform is inexpensive, highly efficient, and benefits from the widespread natural habitats of jellyfish. The demonstrated performance of these biohybrid robots suggests an opportunity to expand the set of robotic tools for comprehensive monitoring of the changing ocean.

Is thermal sensitivity affected by predation risk? A case study in tadpoles from ephemeral environments.

Changes in environmental temperature may induce variations in thermal tolerance and sensitivity in ectotherm organisms. These variations generate plastic responses that can be analyzed by examining their Thermal Performance Curves (TPCs). Additionally, some performance traits, like locomotion, could be affected by other factors such as biological interactions (e.g., predator-prey interaction). Here, we evaluate if the risk of predation modifies TPCs in Mendoza four-eyed frog (Pleurodema nebulosum, Burmeister, 1861) and Guayapa's four-eyed frog (Pleurodema guayapae, Barrio, 1964), two amphibian species that occur in ephemeral ponds in arid environments. We measured thermal tolerances and maximum swimming velocity at six different temperatures in tadpoles under three situations: control, exposure to predator chemical cues, and exposure to conspecific alarm cues. TPCs were fitted using General Additive Mixed Models. We found that curves of tadpoles at risk of predation differed from those of control mainly in thermal sensitivity parameters. Our work confirms the importance of biotic interactions have in thermal physiology.

Kinematics and muscle activity of pectoral fins in rainbow trout (Oncorhynchus mykiss) station holding in turbulent flow.

Pectoral fins play a crucial role in fish locomotion. Despite fishes living in complex fluid environments that exist in rivers and tidal flows, the role of the pectoral fins in navigating turbulent flows is not well understood. This study investigated the kinematics and muscle activity of pectoral fins in rainbow trout as they held station in the unsteady flows behind a D-section cylinder. We observed two distinct pectoral fin behaviors, one during braking and the other during Kármán gaiting. These behaviors were correlated to whole-body movements in response to the hydrodynamic conditions of specific regions in the cylinder wake. Sustained fin extensions during braking, where the fin was held out to maintain its position away from the body and against the flow, were associated with the cessation of forward body velocity, where the fish avoided the suction region directly downstream of the cylinder. Transient fin extensions and retractions during Kármán gaiting controlled body movements in the cross-stream direction. These two fin behaviors had different patterns of muscle activity. All braking events required recruitment from both the abductor and adductor musculature to actively extend a pectoral fin. In contrast, over 50% of fin extension movements during Kármán gaiting proceed in the absence of muscle activity. We reveal that in unsteady fluid environments, pectoral fin movements are the result of a complex combination of passive and active mechanisms that deviate substantially from canonical labriform locomotion, the implications of which await further work on the integration of sensory and motor systems.

The impact of swimming training on physiological and psychological indicators in individuals of different age groups: a cross-sectional study

Swimming training is a kind of aquatic exercise that has been shown to be beneficial to physical fitness at any age. This study aimed to determine how mental and physical aspects of swimming affect aerobic and anaerobic capacity describes the physiologicaland psychological effects of swimming training at different ages. This studyexamines how swimming impacts youthful and elderly cardio-respiratory fitness, muscular strength, flexibility, and body composition. A correlation and stepwise regression analysis was performed on the information gathered from a RESTQ-76 sport questionnaire, aHeart Rate Variability (HRV) test, and the efforts of swimmers to improve their aerobic and anaerobic swimming performance. We also investigate the benefits that swimming has on lowering stress, boosting self-esteem, and improving mental health for people of varying ages. We useSPSS version 17.0 was used for the statistical analysis. An examination of the relevant research reveals that swimmers of all ages enjoy significant advantages as a result of their training, including enhancements to their physical and mental health. In that case, they can be able to tailor swimming programs to match the changing physiological and psychological needs of their swimmers. Findings from this study add to a growing body of evidence that open-water swimming is perceived to have positive effects on participants' mental and physical health regardless of age and can be used to inform co-created policy formation to advance outdoor recreation possibilities that are safer, healthier, and more sustainable about this expanding outside activity (AU)

Novel peptides from sea cucumber intestines hydrolyzed by neutral protease alleviate exercise-induced fatigue via upregulating the glutaminemediated Ca2+ /Calcineurin signaling pathway in mice.

Sea cucumber intestines are considered a valuable resource in the sea cucumber processing industry due to their balanced amino acid composition. Studies have reported that peptides rich in glutamate and branched-chain amino acids have anti-fatigue properties. However, the function of the sea cucumber intestine in reducing exercise-induced fatigue remains unclear. In this study, we enzymatically hydrolyzed low molecular weight peptides from sea cucumber intestines (SCIP) and administered SCIP orally to mice to examine its effects on exercise-induced fatigue using swimming and pole-climbing exhaustion experiments. The results revealed that supplementation with SCIP significantly prolonged the exhaustion time of swimming in mice, decreased blood lactate and urea nitrogen levels, and increased liver and muscle glycogen levels following a weight-loaded swimming test. Immunofluorescence analysis indicated a notable increase the proportion of slow-twitch muscle fiber and a significant decrease the proportion of fast-twitch muscle fiber following SCIP supplementation. Furthermore, SCIP upregulated mRNA expression levels of Ca2+ /Calcineurin upstream and downstream regulators, thereby contributing to the promotion of skeletal muscle fiber type conversion. This study presents the initial evidence establishing SCIP as a potential enhancer of skeletal muscle fatigue resistance, consequently providing a theoretical foundation for the valuable utilization of sea cucumber intestines.

Effects of caudal fin size on tail-flip jump performance.

Fishes are generally considered to be fully aquatic, but some voluntarily strand themselves on land to escape poor water conditions, predators, or to exploit terrestrial niches. The tail-flip jump is a method of terrestrial locomotion performed by small fishes without apparent morphological specialization, but few studies have investigated the role the caudal fin has on the tail-flip jump. We hypothesized that fish with larger caudal fins would perform shorter individual tail-flip jumps and not be able to sustain jumping in extended terrestrial excursions. Zebrafish (Danio rerio) are an excellent model to investigate this because these fish perform the tail-flip jump and some strains have been selectively bred in the pet trade industry for larger fins. In this study, wildtype and longfin zebrafish were compared because of the larger caudal fins of the longfin zebrafish. Individuals of each strain performed three consecutive jump trials with 48 h between each trial: kinematic, voluntary, and exhaustion. The kinematic trial used a high-speed camera to measure kinematic variables of individual jumps. The voluntary trial recorded each fish's voluntary response to stranding for three minutes. The exhaustion trial recorded the fish's response to be constantly elicited to jump until exhaustion was reached. Despite differences in caudal fin area, there were no differences in the kinematic characteristics of individual jump performances, including jump distance. However, wildtype zebrafish performed more jumps, jumped more than they flopped, and moved a greater total distance in both voluntary and exhaustion trials despite moving for similar durations and reaching exhaustion at similar times. These findings imply that larger fins do not affect a fish's ability to perform individual tail-flip jumps but does cause fish to employ different behavioral strategies when stranded for longer durations on land.

Comparison of Muscle Coordination During Front Crawl and Backstroke With and Without Swimmer's Shoulder Pain.

BACKGROUND: Shoulder pain, known as swimmer's shoulder, is the most common injury for swimmers. Studies that have analyzed muscle activity have focused on the shoulder joint. However, the whole-body muscle coordination of swimmers with swimmer's shoulder is not clear, although swimming requires movements of the upper limbs, trunk, and lower limbs to obtain propulsive force. This study investigated differences in muscle coordination between swimmers with and without swimmer's shoulder during the front crawl and backstroke using muscle synergy analysis. HYPOTHESIS: Swimmers with swimmer's shoulder have muscle synergies differing from those without it. STUDY DESIGN: Case-control study. LEVEL OF EVIDENCE: Level 4. METHODS: A total of 20 elite swimmers who regularly swam front crawl and backstroke were included (swimmer's shoulder, n = 8; control, n = 12). Muscle synergy data were analyzed using the nonnegative matrix factorization method and compared between groups. RESULTS: For both front crawl and backstroke, there were 2 synergies in the control group and 3 synergies in the swimmer's shoulder group. During recovery, the control group showed coordinated triceps brachii, serratus anterior, upper trapezius, lower trapezius, internal oblique, and external oblique muscles activities; however, in the swimmer's shoulder group, the contribution of the upper limbs decreased and only that of the trunk muscles increased. CONCLUSION: A comparison of muscle coordination during the front crawl and backstroke performed by swimmers with and without swimmer's shoulder revealed that coordination differed during the recovery phase. During both front crawl and backstroke, the swimmer's shoulder group could not maintain coordination with the upper limb when the trunk rolled, and split synergy was formed between the upper limbs and trunk. CLINICAL RELEVANCE: Because coordination of the upper limbs and trunk is important during the recovery phase of front crawl and backstroke, swimmer's shoulder rehabilitation should introduce exercises to improve their coordination between the upper limbs and the trunk.

Physiological Responses and Swimming-Performance Changes Induced by Altering the Sequence of Training Sets.

PURPOSE: Interval-training sets may be applied in a different sequence within a swimming training session. The aim of this study was to investigate the effect of different set sequences on performance and physiological responses in a training session. METHODS: Twelve highly trained male swimmers performed 4 sessions in randomized order. Each session included a different combination of 2 training sets: set A-set C, set C-set A, set B-set C, or set C-set B. Set A consisted of 8 × 200 m at speed corresponding to lactate threshold (30-s recovery), set B included 8 × 100 m at maximum aerobic speed (30-s recovery), and set C included 4 × 50-m all-out swimming (2-min recovery). Performance and physiological responses (lactate concentration, pH, base excess, bicarbonate, heart rate, and heart-rate variability) were measured. RESULTS: Performance in each set was similar between sessions irrespective of set sequence. Blood lactate, heart rate, and acid-base responses during set C were similar in all sessions, but blood lactate was higher in sets A and B during C-A and C-B sessions (P = .01). The overall blood lactate and acid-base response was higher in C-A and C-B sessions compared with A-C and B-C sessions, respectively (P = .01). Heart-rate variability in each set, separately as well as the overall session effect, did not differ and was thus independent to the set sequence applied. CONCLUSIONS: Training sessions including all-out swimming as a first set increase the magnitude of metabolic responses to the subsequent aerobic-dominated training set.

Protocol for using UV stimuli to evoke prey capture strikes in head-fixed zebrafish larvae.

Hunting in larval zebrafish begins with eye convergence and orienting turns, proceeds to approach swims, and ends with the strike, where larvae consume the prey. Here, we describe a protocol to present UV stimuli to zebrafish, which greatly increases the occurrence of hunting initiation and strikes. We also describe how we record and analyze strike behavior in head-fixed larvae. Our goals are to increase the robustness of prey capture and to allow other labs to implement the strike behavioral assay. For complete details on the use and execution of this protocol, please refer to Khan et al. (2023).1.

The effect of fishing-capture stress on the oxygen uptake rate and swimming activity of the holocephalan Callorhinchus milii.

Overfishing, capture mortality, and consequences following the release of surviving animals represent severe threats to chondrichthyans. Although holocephalans are common bycaught and discarded species, other than postrelease mortality, little is known of fishing capture stress impacts. The stress response elicited after capture, essential to increase survival chances, is energetically demanding and affects the amount of energy available for other biological activities, with potential long-term impairments. We measured the effect of 30-min simulated gillnet capture on oxygen uptake rate (MO2 ), a proxy for metabolic rate and energy use, on recovery pattern, and on swimming activity of elephant fish (Callorhinchus milii). Immediately after simulated capture, Active and Inactive MO2 , measured during swimming and resting periods, respectively, were 27.5% and 43.1% lower than precapture values. This metabolic decline is likely an adaptation for reducing the energy allocated to non-essential activities, thus preserving it to sustain the stress response and processes essential for immediate survival. Supporting this, after gillnet capture, animals decreased their swimming time by 26.6%, probably due to a reduction in the energy allocated to movement. After 7 days, swimming activity and both Inactive MO2 and Active MO2 returned to precapture values. Although metabolic decline may enhance survival chances, the associated decreased swimming activity might increase predation risk and slow the physiological recovery after a fishing event. Moreover, some of the activities involved in Inactive MO2 are fundamental for life maintenance and therefore its depression after a capture event might have long-term repercussions for life sustenance and health.

Neural Endophenotype Assessment in Zebrafish Larvae Using Optomotor and ZebraBox Locomotion Assessment.

Due to the highly conserved genetics across the central nervous system, the easily probed visual system can act as an endophenotype for assessing neurological function. Here, we describe a psychophysics approach to assess visually driven swimming behavior in the high-throughput zebrafish genetic model system. We use the optomotor response test together with general locomotion behavior to assess neural processing while excluding motor defects related to muscle function.

Swimming alters some proteins of skeletal muscle tissue in rats with Alzheimer-like phenotype.

OBJECTIVES: Exercise training plays a significant role in preventing the destruction of central nerve neurons and muscle atrophy. The purpose of the present study was to investigate the effect of a period of swimming training on the expression of Neural cell adhesion molecule (NCAM), Semaphorin 3A (SEMA3A), and Profilin-1 (PFN1) proteins in the gastrocnemius muscle of Alzheimer-like phenotype rats. METHODS & MATERIALS: 32 Wistar males were (6 weeks of age) divided into four groups: Healthy Control (HC), Alzheimer-like phenotype's Control (AC), Healthy Training (HT), and Alzheimer-like phenotype's Training (AT). Alzheimer-like phenotypes were induced by beta-amyloid injection in the hippocampus. The training program consisted of 20 swimming sessions. Gastrocnemius muscle was removed after the intervention, and NCAM, SEMA3A, and PFN1 proteins were measured by the immunohistoflorescent method. RESULTS: The results showed that SEMA3A was increased (p = 0.001), and NCAM (p = 0.001), and PFN1 (p = 0.001) were decreased in AC compared to the HC group. Also, the results showed that NCAM (p = 0.001) and Pfn1 (p = 0.002) increased in the HT group compared to HC, and the NCAM (p = 0.001) and Pfn1 (p = 0.002) in AT group compared to AC (p = 0.001) increased significantly, while SEMA3A was reduced in the HT group compared to HC (p = 0.001) and AT group compared to AC (p = 0.001) CONCLUSION: Swimming effectively improves axon regeneration and neuronal formation in motor neurons and, therefore, can be an effective intervention to prevent and control the complications of Alzheimer-like phenotype.

Diving into Recovery. The Effects of Different Post-Competition Protocols for Enhancing Physio-Psychological Parameters in National Level Youth Swimmers.

The purpose of this study was to elucidate whether a specific approach regarding active swimming recovery could better promote psycho-physiological recovery right after competing in a high-level swimming race. To achieve this, we recruited 50 national level youth swimmers, randomly and equally assigning them to two groups, named "experimental" and "coach prescribed". Each group performed a specific post-competition recovery protocol, consisting of different swimming paces, rest times, self-management of the exercises. We gathered data about blood lactate (BL), heart rate (HR), and rate of perceived exertion (RPE) at two different moments, the first moment right after the swimming competition (named post-competition phase), the second moment right after swimming the respective recovery protocol assigned (named post-recovery phase). A mixed MANOVA with Tukey HSD post-hoc analysis revealed no significant differences between the experimental and coach-prescribed groups in BL, HR, and RPE at the post-competition phase. At the post-recovery phase, however, the experimental group presented lower BL levels than the coach-prescribed group (2.40 ± 1.18 vs. 4.29 ± 2.07 mmol/L, p < 0.05). Finally, we found no interaction of swimming race ranking on recovery capacities. We conclude that for immediate improvement of BL in a wide range of high-level swimmers, an efficient recovery protocol should consist of several paces, high volumes, fixed and short rest times, whereas the widely popular self-managed, lower intensity approach does not seem as equally effective. Our study advances the development of novel recommendations for optimizing immediate fatigue management in competitive swimming.

Energetic and Cognitive Demands of Treading Water: Effects of Technique and Expertise.

Being able to tread water effectively can improve the likelihood of survival following accidental immersion. People tread water in various ways, ranging from rudimentary 'doggy-paddle' to more elaborate techniques like the eggbeater, but little is known about the energetic and cognitive requirements of treading water. We therefore aimed to measure the demands of treading water techniques for people of different experience levels. Three cohorts, comprising 21 adult water treading experts (water polo players), 15 intermediate swimmers and 16 inexperienced swimmers, treaded water for 3 min each using four different techniques while cognitive and energetic economy measures were taken. For inexperienced swimmers, the flutter kick and breaststroke patterns produced the lowest self-reported physical and task load (rating of perceived exertion, NASA task load index), while cognitive (probe reaction time), cardiac (heart rate) and metabolic (oxygen consumption) load did not differ between techniques. In contrast, for expert water treaders, both breaststroke and eggbeater patterns produced lower cognitive, cardiac and metabolic loads. For intermediate swimmers, breaststroke resulted in the lowest cardiac and metabolic loads, as well as self-reported task load. Probe reaction time was highest while performing the eggbeater technique, indicating that this technique was challenging to coordinate and cognitively demanding. While the energetic demands of antiphase kicking patterns (such as eggbeater in experts or flutter kick in beginners) may be similarly low, the symmetric coordination of upright breaststroke may explain why this pattern's cognitive economy was favourable for all groups. As the eggbeater can be challenging to perform for many people, an upright breaststroke technique is an adequate alternative to adopt in survival situations.