Follow-Up Weekly Training Distribution and Accumulated Internal Load Effects on Young Football Players' Well-Being, Physical Fitness, and Technical Performance.

This study aimed to quantify the relationships among internal training load, wellness, physiological, isokinetic profile, and technical performance and assessed changes before and after a six-week pre-season structured combining physical fitness, small-sided-game and skill-based training program in young soccer players. Forty-five national-level young male soccer players (16.8 ± 0.9 years) were evaluated. There were no significant correlations between the wellness index and the physiological, isokinetic, or specific soccer skill parameters. Moderate correlations were observed between fatigue and stress (r = 0.47, moderate, p < 0.01), fatigue and average muscle soreness (r = 0.38, moderate, p = 0.01), and a large correlation between average stress and muscle soreness (r = 0.53, large, p < 0.01) were presented. All physiological, isokinetic, and technical parameters improved after a six-week pre-season training program (0.1 to -61.0%). Significant alterations in the physiological domain were observed after a six-week period, particularly in the fatigue index of the Bangsbo sprint test, YO-YO IR1 performance, and YO-YO peak La- (p < 0.01; -61.0%, 25.3%, and -19.8%, respectively). As such, the implementation of structured training and the monitoring of stress responses can lead to appropriate adaptation and balancing in the psychological and physical well-being of young national-level soccer players, particularly in the pre-season period.

Swimming With the COSMED AquaTrainer and K5 Wearable Metabolic System in Breath-by-Breath Mode: Accuracy, Precision, and Repeatability.

PURPOSE: To compare ventilatory and cardiorespiratory responses between the COSMED AquaTrainer coupled with the K4b2 and K5 wearable metabolic systems in breath-by-breath mode over a wide range of swimming speeds. METHODS: Seventeen well-trained master swimmers performed 2 front-crawl 7 × 200-m incremental intermittent protocols (increments of 0.05 m·s-1 and 30-s rest intervals, with a visual pacer) with AquaTrainer coupled with either K4b2 or K5. RESULTS: Post hoc tests showed that swimming speed was similar (mean diff.: -0.01 to 0.01 m·s-1; P = .73-.97), repeatable (intraclass correlation coefficient: .88-.99; P < .001), highly accurate, and precise (agreement; bias: -0.01 to 0.01 m·s-1; limits: -0.1 to 0.1 m·s-1) between all conditions. Ventilatory and cardiorespiratory responses were highly comparable between all conditions, despite a "small" effect size for fraction of expired carbon dioxide at the sixth 200-m step (0.5%; ηp2=.12; P = .04) and carbon dioxide production at the fifth, sixth, and seventh 200-m steps (0.3-0.5 L·min-1; ηp2=.11-.17; P = .01-.05). We also observed high accuracy, which was greater for tidal volume (0.0-0.1 L), minute ventilation (-3.7 to 5.1 L·min-1), respiratory frequency (bias: -2.1 to 1.9 breaths·min-1), and oxygen uptake (0.0-0.2 L·min-1). Bland-Altman plots showed that the distribution inside the limits of agreement and their respective 95% CIs were consistent for all ventilatory and cardiorespiratory data. The repeatability (intraclass correlation coefficient) of tidal volume (.93-.97), minute ventilation (.82-.97), respiratory frequency (.68-.96), fraction of expired carbon dioxide (.85-.95), carbon dioxide production (.77-.95), fraction of expired oxygen (.78-.92), and oxygen uptake (.94-.98) data ranged from moderate to excellent (P < .001-.05). CONCLUSIONS: Swimming with the AquaTrainer coupled with K5 (breath-by-breath mode) yields accurate, precise, and repeatable ventilatory and cardiorespiratory responses when compared with K4b2 (previous gold standard). Swimming support staff, exercise and health professionals, and researchers can now relate differences between physiological capacities measured with the AquaTrainer while coupled with either of these 2 devices.

Bioenergetic Analysis and Fatigue Assessment During the Fran Workout in Experienced Crossfitters.

AIM: To quantify the physiological demands and impact of muscle function t of the Fran workout, one of the most popular CrossFit benchmarks. METHODS: Twenty experienced CrossFitters-16 male: 29 (6) years old and 4 female: 26 (5) years old- performed 3 rounds (with 30-s rests in between) of 21-21, 15-15, and 9-9 front squats to overhead press plus pull-up repetitions. Oxygen uptake and heart rate were measured at baseline, during the workout, and in the recovery period. Rating of perceived exertion, blood lactate, and glucose concentrations were assessed at rest, during the intervals, and in the recovery period. Muscular fatigue was also monitored at rest and at 5 minutes, 30 minutes, and 24 hours postexercise. Repeated-measures analysis of variance was performed to compare time points. RESULTS: Aerobic (52%-29%) and anaerobic alactic (30%-23%) energy contributions decreased and the anaerobic lactic contribution increased (18%-48%) across the 3 rounds of the Fran workout. Countermovement jump height decreased by 8% (-12 to -3) mean change (95% CI), flight duration by 14% (-19 to -7), maximum velocity by 3% (-5 to -0.1), peak force 4% (-7 to -0.1), and physical performance (plank prone 47% [-54 to -38]) were observed. CONCLUSIONS: It appears that the Fran workout is a physically demanding activity that recruits energy from both aerobic and anaerobic systems. This severe-intensity workout evokes substantial postexercise fatigue and corresponding reduction in muscle function.

The Effect of a Hydroxytyrosol-Rich, Olive-Derived Phytocomplex on Aerobic Exercise and Acute Recovery.

There is current scientific interest in naturally sourced phenolic compounds and their potential benefits to health, as well as the effective role polyphenols may provide in an exercise setting. This study investigated the chronic effects of supplementation with a biodynamic and organic olive fruit water phytocomplex (OliPhenolia® [OliP]), rich in hydroxytyrosol (HT), on submaximal and exhaustive exercise performance and respiratory markers of recovery. Twenty-nine recreationally active participants (42 ± 2 yrs; 71.1 ± 2.1 kg; 1.76 ± 0.02 m) consumed 2 × 28 mL∙d−1 of OliP or a taste- and appearance-matched placebo (PL) over 16 consecutive days. Participants completed a demanding, aerobic exercise protocol at ~75% maximal oxygen uptake (V˙O2max) for 65 min 24 h before sub- and maximal performance exercise tests prior to and following the 16-day consumption period. OliP reduced the time constant (τ) (p = 0.005) at the onset of exercise, running economy (p = 0.015) at lactate threshold 1 (LT1), as well as the rating of perceived exertion (p = 0.003) at lactate turnpoint (LT2). Additionally, OliP led to modest improvements in acute recovery based upon a shorter time to achieve 50% of the end of exercise V˙O2 value (p = 0.02). Whilst OliP increased time to exhaustion (+4.1 ± 1.8%), this was not significantly different to PL (p > 0.05). Phenolic compounds present in OliP, including HT and related metabolites, may provide benefits for aerobic exercise and acute recovery in recreationally active individuals. Further research is needed to determine whether dose-response or adjunct use of OliP alongside longer-term training programs can further modulate exercise-associated adaptations in recreationally active individuals, or indeed support athletic performance.

The effect of combining HIIT and dry-land training on strength, technique, and 100-m butterfly swimming performance in age-group swimmers: a randomized controlled trial.

Combined interventions of pool-based and dry-land workouts are a common practice in swimming training. However, the effects on strength, technique and swimming performance are still not clear. Through a randomized controlled trial study, we investigated the effect of combining high intensity interval training (HIIT) and maximum strength training (MST) on strength, technique and 100-m butterfly swimming performance. Competitive age-group swimmers (N = 22, males) were randomly divided into two groups. The experimental group (EG: 14.1 ± 0.3 years old) performed 8 weeks of combined short-moderate HIIT and MST. The control group (CG: 14.5 ± 0.3 years old) subjects performed their usual training. Muscular strength, technique and swimming performance were evaluated before and after 8 weeks. Substantial improvements were observed in maximum muscle strength (mean diff: 22-28%; p < 0.001; d = 3.25-3.61), technique (p < 0.05; d = 0.98-1.96) and 100-m butterfly swimming performance (3.5%; p = 0.001; d = 1.81) when combining HIIT and MST during 8 weeks. Combining short-moderate HIIT and MST during 8 weeks can enhance maximum muscular strength, technique, and 100-m butterfly swimming performance. Coaches should adjust training programmes accordingly since it could yield important differences in swimming performance during competitions.

Biophysical Impact of 5-Week Training Cessation on Sprint Swimming Performance.

PURPOSE: To assess changes in swimming performance, anthropometrics, kinematics, energetics, and strength after 5-week training cessation. METHODS: Twenty-one trained and highly trained swimmers (13 males: 17.4 [3.1] y; 50-m front crawl 463 [77] FINA points; 8 females: 16.7 [1.7] y; 50-m front crawl 535 [48] FINA points) performed a 50-m front-crawl all-out swim test, dryland and pool-based strength tests, and 10-, 15-, 20-, and 25-m front-crawl all-out efforts for anaerobic critical velocity assessment before and after a 5-week training cessation. Heart rate and oxygen uptake (V˙O2) were continuously measured before and after the 50-m swim test (off-kinetics). RESULTS: Performance was impaired 1.9% (0.54 s) for males (P = .007, d = 0.91) and 2.9% (0.89 s) for females (P = .033, d = 0.93). Neither the anthropometrical changes (males: r2 = .516, P = .077; females: r2 = .096, P = .930) nor the physical activities that each participant performed during the off-season (males: r2 = .060, P = .900; females: r2 = .250, P = .734) attenuated performance impairments. Stroke rate and clean swimming speed decreased (P < .05), despite similar stroke length and stroke index (P > .05). Blood lactate concentrations remained similar (P > .05), but V˙O2 peak decreased in females (P = .04, d = 0.85). Both sexes showed higher heart rate before and after the 50-m swim test after 5 weeks (P < .05). Anaerobic metabolic power deterioration was only observed in males (P = .035, d = 0.65). Lower in-water force during tethered swimming at zero speed was observed in males (P = .033, d = 0.69). Regarding dryland strength, lower-body impairments were observed for males, while females showed upper-body impairments (P < .05). CONCLUSIONS: A 5-week training cessation yielded higher heart rate in the 50-m front crawl, anaerobic pathways, and dryland strength impairments. Coaches should find alternatives to minimize detraining effects during the off-season.

Supply of Antioxidants vs. Recruit Firefighters' Cellular Immune Status: A Randomized Double-Blinded Placebo-Controlled Parallel-Group Trial.

Background: Physical exercise can affect the immune system. We studied the effect of antioxidants on hematological and immune biomarkers after heavy training. Methods: 24 well-trained and well-fed male firefighters were randomly divided into supplemented and placebo groups, and tested for immunology-related variables using venous blood samples in the fasting state, pre- (M1) and post- (M2) five weeks of daily micronutrient supplementation (15 mg of beta-carotene, 200 mg of vitamin C, 136 mg of vitamin E, 200 µg of selenium, 15 mg of zinc, 100 mg of magnesium). Total leukocytes and a differential count for five populations were determined using standard procedures (MAXM­Beckman Coulter Diagnostics; Brea, CA, USA). Lymphocyte subsets were determined through immunophenotyping. Results: Although all values were within the normal range for healthy adults and athletes in the supplemented group (SG), mean CD3+CD8+, CD8+ and CD16+CD56+ decreased (p < 0.05; small to moderate effects), while mean CD4+, CD19+ and CD4+/CD8+ increased (p < 0.05; small effects) after five-weeks. Regarding the placebo group (PG), higher total leukocyte count (p < 0.05; trivial effect) and natural killer cells percentage (CD16+CD56+; p < 0.05; moderate effect) were observed when comparing M1 and M2. Conclusions: Antioxidants supplementation did not alter well-fed male firefighters recruit firefighters' immune cell response during the five-week physical training program.

Biomechanical Features of Backstroke to Breaststroke Transition Techniques in Age-Group Swimmers.

This study aimed to identify the biomechanical features of backstroke to breaststroke transition techniques (open, somersault, bucket, and crossover) in age-group swimmers. Eighteen preadolescent swimmers (12.2 ± 0.4 years old and 3-4 Tanner stages) underwent 4 weeks of systematic contextual interference training, comprising 16 sessions (40 min·session-1). Soon after, experimental testing was conducted where swimmers randomly performed 12 × 15 m maximal turns (composed of 7.5 m turn-in and 7.5 m turn-out of the wall segments), three in each transition technique. Kinematical, kinetic, and hydrodynamic variables were assessed with a dual-media motion capture system (12 land and 11 underwater cameras), triaxial underwater force plates, and inverse dynamics. Variables were grouped in turn-in (approach and rotation) and turn-out (wall contact, gliding, and pull-out) phases, with factor analysis used to select the variables entering on multiple regressions. For the turn-in phase, 86, 77, 89, and 87% of the variance for open, somersault, bucket, and crossover turning techniques, respectively, was accounted by the 7.5 and 2.5 m times, mean stroke length, and rotation time. For the turn-out phase, first gliding distance and time, second gliding depth, turn-out time, and dominating peak_Z push-off force accounted for 93% in open turn, while wall contact time, first gliding distance, breakout distance and time, turn-out time, dominating peak_Y push-off force, and second gliding drag coefficient accounted for 92% in a somersault turn. The foot plant index, push-off velocity, second gliding distance, and turn-out time accounted for 92% in bucket turn while breakout and turn-out time, non-dominating peak_Y and peak_Z push-off force, first and second gliding drag force and second gliding drag coefficient accounted for 90% in crossover turn, respectively. The findings in this study were novel and provided relevant biomechanical contribution, focusing on the key kinematic-temporal determinant during turn-in, rotation, and push-off efficacy, and the kinetic and hydrodynamic during turn-out, which would lead to improved backstroke to breaststroke transition techniques in 11-13 years-old age-group swimmers.

The Impact of a Swimming Training Season on Anthropometrics, Maturation, and Kinematics in 12-Year-Old and Under Age-Group Swimmers: A Network Analysis.

Understanding fluctuations and associations between swimming performance-related variables provide strategic insights into a swimmer's preparation program. Through network analysis, we verified the relationships between anthropometrics, maturation, and kinematics changes (Δ) in 25-m breaststroke (BREAST) and butterfly (FLY) swimming performance, before and after a 47-week swimming training season. Twenty age-group swimmers (n =11 girls: 10.0 ± 1.3 years and n = 9 boys: 10.5 ± 0.9 years) performed a 25-m all-out swim test (T25) in BREAST and FLY techniques, before and after 47 weeks. Three measures of centrality, transformed into a z-score, were generated: betweenness, closeness, and strength. Data were compared (t-test) and effect sizes were identified with Hedges' g. Large effect sizes were observed for swimming performance improvements in BREAST (32.0 ± 7.5 to 24.5 ± 3.8 s; g = 1.26; Δ = -21.9 %) and FLY (30.3 ± 7.0 to 21.8 ± 3.6 s; g = 1.52; Δ = -26.5 %). Small to moderate effect sizes were observed for anthropometric changes. Moderate effect size was observed for maturity offset changes (-2.0 ± 0.9 to -1.3 ± 1.0; g = 0.73; Δ = 50.9 ± 281 %). Changes in maturity offset, stroke rate (SR), and stroke length for both BREAST and FLY swimming speeds were highlighted by the weight matrix. For betweenness, closeness, and strength, changes in arm span (AS) (BREAST) and stroke length (FLY) were remarkable. The dynamic process of athletic development and the perception of complexity of fluctuations and associations between performance-related variables were underpinned, particularly for simultaneous swimming techniques in age-group swimmers.

Case Study: Comparison of Swimsuits and Wetsuits Through Biomechanics and Energetics in Elite Female Open Water Swimmers.

AIM: The authors investigated how the Arena Powerskin R-EVO Closed Back swimsuit and Arena Carbon Triwetsuit (full-sleeve wetsuit), both approved by the Fédération Internationale de Natation (FINA) regulations, affect biomechanics and energetics of 3 elite female open water (OW) swimmers at maximal and 4 submaximal swimming intensities. METHODS: Three elite female OW swimmers (OW1 = 24 y, 1.64 m, 60 kg; OW2 = 23 y, 1.69 m, 65 kg; OW3 = 27 y, 1.63 m, 64.5 kg) were tested 1 week prior to a FINA/CNSG (China National Sports Group) Marathon Swim World Series event and 40 days before the 18th FINA World Championships 2019. Each OW swimmer completed 2 identical testing sessions, one with a swimsuit and other with a wetsuit, involving shoulder flexion power output assessed from medicine-ball throw, maximal performance and drag coefficient assessment, and an incremental intermittent swim test at 4 different relative intensities. RESULTS: Estimated peak oxygen uptake was 4.4 L·min-1 for OW1, 5.6 L·min-1 for OW2, and 5.0 L·min-1 for OW3. Despite a distinct behavior observed on index of coordination for OW3, a null index of synchronization, increased stroke rate (mean difference = 2%-8%), reduced drag factor (minimum = -14%; maximum = -30%), lower energy cost (mean difference = -2% to -6%), and faster performance (mean difference = 2% to 3%) were observed with the wetsuit compared with swimsuit for all elite OW swimmers. CONCLUSION: The wetsuit enhances submaximal swimming performance, and this increase is dependent on the OW swimmer's characteristics. The higher stroke rate and lower stroke length detected with wetsuit could be related to movement constraints imposed by the suit.

200-m front crawl performance over a training season in 12 years and underage-group swimmers: growth and kinematics effects

Abstract Aims: analyze kinematics, anthropometrics, and maturation during a training season in 12 y and underage-group swimmers, quantifying changes and estimating their contributions to the 200-m maximal front crawl time trial test (T200) (time trial/fixed distance), as an event representative of the swimming performance. Methods: Nineteen age-group swimmers (11 girls and 8 boys; age 10.0 ± 1.3 y and 10.6 ± 1.0 y) performed a T200 four times during the training season. Changes in kinematic and anthropometric variables throughout the season were calculated. We applied generalized estimating equations to compare the variables over the four experimental tests. Multiple linear regressions were applied to identify the most influential variables and the relative contribution of anthropometrics and kinematics to swimming performance of T200 at baseline (pre-season) and after (using delta values) each macrocycle. Results: Large improvements (d = 1.76) were observed in the T200's performance (from 85.5 ± 38.2 at pre-season to 175.2 ± 50.1 FINA points at the end season). A gender effect was not identified. Stroke rate, stroke length, and stroke index explained, respectively 59, 23, and 17% of the T200 performance changes along the season (R2 = 0.81; F = 26.9; p < 0.001; Durbin-Watson: 1.5). Anthropometric was not related to performance changes, with kinematic being the most determinant factor. Conclusion: Kinematical approaches must be carefully considered by coaches when planning 12 y and underage-group swimmers training programs.

Swimming with Swimsuit and Wetsuit at Typical vs. Cold-water Temperatures (26 vs. 18 ℃).

This study aimed to compare three swimming conditions in a swimming flume with water at 26 ℃ (using swimsuit) and 18 ℃ (randomly with swimsuit and wetsuit). Seventeen swimmers (32.4±14.7 years old, 175.6±0.06 cm height, and 70.4±9.8 kg body mass) performed three bouts until exhaustion at a 400-m front crawl pace (24 h intervals). ANOVA repeated measures compared the experimental conditions. Swimming at 26 ℃ with swimsuit evidenced a higher metabolic demand (total energy expenditure; (E)), comparing to 18 ℃ swimsuit (p=0.05) and with 18 ℃ wetsuit (p=0.04). The 26 ℃ swimsuit condition presented higher peak oxygen uptake (VO2peak), blood lactate concentrations ([La-]peak), rate of perceived exertion (RPE), maximal heart rate (HRmax), anaerobic lactic energy (AnL), E, energy cost (C), V̇O2 amplitude (Ap), and stroke rate (SR), but lower stroke length (SL) and stroke index (SI) than 18 ℃ wetsuit. The 18 ℃ swimsuit condition (comparing to wetsuit) lead to higher V̇O2peak, [La-]peak, HRmax, E, C, Ap, and SR but lower SL and SI. Swimming at aerobic power intensity with swim and wetsuit at 18 ℃ does not induce physiologic and biomechanical disadvantages compared to 26 ℃. The results suggested that the use of wetsuit might increase performance at 18 ℃ water temperature for competitive master swimmers. Its use is thus recommended in open water swimming competitions when the water temperature is 18-20 ℃.

Strength Training versus Stretching for Improving Range of Motion: A Systematic Review and Meta-Analysis.

(1) Background: Stretching is known to improve range of motion (ROM), and evidence has suggested that strength training (ST) is effective too. However, it is unclear whether its efficacy is comparable to stretching. The goal was to systematically review and meta-analyze randomized controlled trials (RCTs) assessing the effects of ST and stretching on ROM (INPLASY 10.37766/inplasy2020.9.0098). (2) Methods: Cochrane Library, EBSCO, PubMed, Scielo, Scopus, and Web of Science were consulted in October 2020 and updated in March 2021, followed by search within reference lists and expert suggestions (no constraints on language or year). Eligibility criteria: (P) Humans of any condition; (I) ST interventions; (C) stretching (O) ROM; (S) supervised RCTs. (3) Results: Eleven articles (n = 452 participants) were included. Pooled data showed no differences between ST and stretching on ROM (ES = -0.22; 95% CI = -0.55 to 0.12; p = 0.206). Sub-group analyses based on risk of bias, active vs. passive ROM, and movement-per-joint analyses showed no between-protocol differences in ROM gains. (4) Conclusions: ST and stretching were not different in their effects on ROM, but the studies were highly heterogeneous in terms of design, protocols and populations, and so further research is warranted. However, the qualitative effects of all the studies were quite homogeneous.

The impact of a single surfing paddling cycle on fatigue and energy cost.

Surfing is one additional sport proposed by the Tokyo 2020 Organizing Committee. Surprisingly, substantial efforts to understand surfing energetics are recent, and the impact of a single surfing paddling cycle on fatigue and energy cost is still not clear. Since surfing paddling technique is highly specific, experiments in real practice conditions are necessary to provide deeper insights. Through a biophysical approach, biomechanical and energetics responses of surfing paddling were quantified and compared from 16 competitive male surfers (23.5 ± 10.0 years old, 65.3 ± 11.4 kg and 1.72 ± 0.01 m) during two sets (PRE and POST) of 10 s all-out tethered paddling plus 20 m sprint paddling, interposed by 6 min of endurance paddling. Faster surfers presented lower energy cost during sprint PRE (r2 = 0.30, p = 0.03) and endurance (r2 = 0.35, p = 0.02) relative surfing paddling velocities. Although the energy cost was higher for a lower velocity at maximal paddling velocity POST, the energy cost of surfing paddling increased with absolute velocity according to a power function (R2 = 0.83). Our results suggest that fatigue seems to occur even following a single surfing paddling cycle. Developing a powerful and endurable metabolic base while reducing energy cost during surfing paddling should be seen as key factors in surfing training programs.

Multi-Micronutrient Supplementation and Immunoglobulin Response in Well-Fed Firefighters.

Intensive physical training programs can affect the immune system. This study aims to verify the multi-micronutrient supplementation effects on serum immunoglobulins levels prior to and after a five-week physical training program. Twenty-four male recruit firefighters were randomly allocated into supplemented (with Prisfar Ever-Fit Plus over 35 consecutive days) and placebo groups (n=12 each). Serum immunoglobulins G, A, and M were assessed. Supplementation effect was detected for immunoglobulin G (eta-squared, η 2 : 0.09; p =0.035; power: 0.56), A (η 2 : 0.24; p =0.001; power: 0.95), and M (η 2 : 0.09; p =0.036; power: 0.56). Although immunoglobulin A was different between groups at baseline (mean difference: 42.58; 95%CI: 7.00 to 78.16 mg/dL; p =0.021; d =2.48), within-group (before vs . after five weeks) showed no differences for both supplemented and control groups. In addition, even if immunoglobulin G and M were similar at baseline, immunoglobulin G decreased (mean diff.: 46.4; 95%CI: 6.7 to 86.1 mg/dL; p =0.03; d =0.74) and immunoglobulin M increased (mean diff.: -10.7; 95%CI: -15.8 to -5.5 mg/dL; p =0.001; d =-1.33) in the control group. Although mean values remained within the reference values, changes observed for immunoglobulin G and M may reflect some immune protection for firefighters engaged in recruit training.

Post-swim oxygen consumption: assessment methodologies and kinetics analysis.

OBJECTIVE: This study aimed at comparing different recovery-based methods to assess the highest exercise oxygen uptake value ([Formula: see text]O2peak) when swimming at low-moderate, heavy and severe intensities. Complementarily, the different recovery curve kinetics were analysed. APPROACH: Eighteen competitive swimmers performed a 5 × 200 m front crawl intermittent protocol (0.05 m · s-1 increments and 3 min intervals), with respiratory gas exchange being continuously measured breath-by-breath during and post-exercise using a portable gas analyser. The directly determined [Formula: see text]O2peak ([Formula: see text]O2dir) was compared with the values obtained by linear and exponential backward extrapolations (of different intervals) and the recovery curve mathematical modelling. MAIN RESULTS: [Formula: see text]O2dir rose with intensity increase: 41.96 ± 6.22, 46.36 ± 6.89 and 50.97 ± 7.28 ml · kg-1 min-1 for low-moderate, heavy and severe swims. Linear and exponential regressions applied to the first 20 s of recovery presented the [Formula: see text]O2peak values closest to [Formula: see text]O2dir at low-moderate (42.80 ± 5.54 vs 42.88 ± 5.58 ml kg-1 min-1), heavy (47.12 ± 4.91 vs 47.48 ± 5.09 ml kg-1 min-1) and severe intensity domains (51.24 ± 6.89 vs 53.60 ± 8.54 ml kg-1 · min-1, respectively; r = 0.5-0.8, p < 0.05). The mono-exponential function was the best fit at low-moderate and heavy intensities, while the bi-exponential function better characterized the severe exercise domain (with a slow component amplitude, time delay and time constant of 6.2 ± 2.3 ml kg-1 min-1, 116.6 ± 24.3 and 39.9 ± 15.2 s, respectively). SIGNIFICANCE: The backward extrapolation of the first 20 s of recovery is the best method to assess the [Formula: see text]O2peak for a large spectrum of swimming intensities. Complementarily, intensity increases imply different recovery curve kinetics, particularly a mono-exponential behaviour for low-moderate and heavy exertions and a bi-exponential dynamics for severe paces.

5 km front crawl in pool and open water swimming: breath-by-breath energy expenditure and kinematic analysis.

PURPOSE: Breath-by-breath energy expenditure during open water swimming has not yet been explored in an ecological environment. This study aimed to investigate and compare energetics and kinematics of 5 km swimming, in both swimming pool and open water conditions. METHODS: Through four independent studies, oxygen uptake ([Formula: see text]2) kinetics, heart rate (HR), blood lactate concentration ([La-]) and glucose level (BGL), metabolic power ([Formula: see text]), energy cost (C) and kinematics were assessed during 5 km front crawl trials in a swimming pool and open water conditions. A total of 38 competitive open water swimmers aged 16-27 years volunteered for this four part investigation: Study A (pool, ten females, 11 males), Study B (pool, four females, six males), Study C (pool case study, one female) and Study D (open water, three females, four males). RESULTS: In the swimming pool, swimmers started with an above average swimming speed (v), losing efficiency along the 5 km, despite apparent homeostasis for [La-], BGL, [Formula: see text]2, [Formula: see text] and C. In open water, swimmers started the 5 km with a below average v, increasing the stroke rate (SR) in the last 1000 m. In open water, [Formula: see text]2 kinetics parameters, HR, [La-], BGL, respiratory exchange ratio and C were affected by the v and SR fluctuations along the 5 km. CONCLUSIONS: Small fluctuations were observed for energetic variables in both conditions, but changes in C were lower in swimming pool than in open water. Coaches should adjust the training plan accordingly to the specificity of open water swimming.