Decreased running economy is not associated with decreased force production capacity following downhill running in untrained, young men.

The present study investigated the relationships between changes in running economy (RE) and indirect muscle damage markers following downhill running (DHR) to test the hypothesis that decreased RE after DHR would be associated with decreases in muscle function. Forty-five young men ran downhill (-15%) for 30 min at the velocity corresponding to 70% of their peak oxygen uptake (VO2peak). Oxygen uptake (VO2) and other parameters possibly associated with RE (blood lactate concentration, perceived exertion, stride length and frequency) were measured during 5-minute level running at the velocity corresponding to 80%VO2peak before, immediately after and 1-3 days after DHR. Knee extensor maximal voluntary contraction torque (MVC), rate of torque development, vertical jump performance, muscle soreness and serum creatine kinase activity were assessed at the same time points. The values of the dependent variables were compared among time points by one-way ANOVAs followed by Bonferroni post-hoc tests when appropriate. Pearson's correlation tests were used to examine relationships between changes in VO2 (RE parameter) and changes in muscle damage parameters. VO2 during the level run increased (p < 0.05) immediately after DHR (18.3 ± 4.6%) and sustained until 2 days post-DHR (11.7 ± 4.2%). MVC decreased (p < 0.05) immediately (-21.8 ± 6.1%) to 3 days (-13.6 ± 5.9%) post-DHR, and muscle soreness developed 1-3 days post-DHR. The magnitude of changes in VO2 did not significantly (p < 0.05) correlate with the changes in muscle damage makers (r = -0.02-0.13) nor stride length (r = -0.05) and frequency (r = -0.05). The absence of correlation between the changes in VO2 and MVC suggests that strength loss was not a key factor affecting RE.

Consumption of An Anthocyanin-Rich Antioxidant Juice Accelerates Recovery of Running Economy and Indirect Markers of Exercise-Induced Muscle Damage Following Downhill Running.

This study examined the effects of anthocyanin-rich antioxidant juice (AJ) on the recovery of exercise-induced muscle damage (EIMD) and the running economy (RE) following downhill running (DHR). Thirty healthy young men were randomly divided into two blinded groups and consumed either AJ or placebo (PLA) for nine days (240 mL twice-a-day). On day 5, the participants from both groups ran downhill (-15%) for 30 min at 70% of their maximal oxygen uptake (VO2max) speeds. The changes in RE (oxygen uptake (VO2) and perceived effort (PE) during 5-min runs at 80%VO2max) and EIMD (isometric peak torque (IPT), muscle soreness (SOR) and serum creatine kinase activity (CK)) were compared over time and between the groups on the 4 days following DHR. VO2 and PE increased (p < 0.05) immediately following DHR for both groups and remained elevated for PLA until 48h post-DHR while fully recovering 24 h post-DHR for AJ. SOR was greater (p < 0.05) for PLA throughout the study. CK increased for both groups and was greater (p < 0.05) for PLA at 96 h post-DHR. IPT decreased for both groups but recovered faster for AJ (72 h) compared to PLA (no full recovery). AJ accelerated recovery of RE and EIMD and should be used in specific contexts, but not chronically.

Isometric pre-conditioning blunts exercise-induced muscle damage but does not attenuate changes in running economy following downhill running.

Running economy (RE) is impaired following unaccustomed eccentric-biased exercises that induce muscle damage. It is also known that muscle damage is reduced when maximal voluntary isometric contractions (MVIC) are performed at a long muscle length 2-4 days prior to maximal eccentric exercise with the same muscle, a phenomenon that can be described as isometric pre-conditioning (IPC). We tested the hypothesis that IPC could attenuate muscle damage and changes in RE following downhill running. Thirty untrained men were randomly assigned into experimental or control groups and ran downhill on a treadmill (-15%) for 30 min. Participants in the experimental group completed 10 MVIC in a leg press machine two days prior to downhill running, while participants in the control group did not perform IPC. The magnitude of changes in muscle soreness determined 48 h after downhill running was greater for the control group (122 ±â€¯28 mm) than for the experimental group (92 ±â€¯38 mm). Isometric peak torque recovered faster in the experimental group compared with the control group (3 days vs. no full recovery, respectively). No significant effect of IPC was found for countermovement jump height, serum creatine kinase activity or any parameters associated with RE. These results supported the hypothesis that IPC attenuates changes in markers of muscle damage. The hypothesis that IPC attenuates changes in RE was not supported by our data. It appears that the mechanisms involved in changes in markers of muscle damage and parameters associated with RE following downhill running are not completely shared.

Comparison of Different Methods for the Swimming Aerobic Capacity Evaluation.

Pelarigo, JG, Fernandes, RJ, Ribeiro, J, Denadai, BS, Greco, CC, and Vilas-Boas, JP. Comparison of different methods for the swimming aerobic capacity evaluation. J Strength Cond Res 32(12): 3551-3560, 2018-This study compared velocity (v) and bioenergetical factors using different methods applied for the swimming aerobic capacity evaluation. Ten elite female swimmers (17.6 ± 1.9 years, 1.70 ± 0.05 m, and 61.3 ± 5.8 kg) performed an intermittent incremental velocity protocol until voluntary exhaustion to determine the v associated with the individual anaerobic threshold (IAnT), ventilatory threshold (VT), heart rate threshold (HRT), lactate threshold fixed in 3.5 mmol·L (LT3.5), and maximal oxygen uptake (V[Combining Dot Above]O2max). Two-to-three 30-minute submaximal constant tests for the v assessment at maximal lactate steady state (MLSS). The v, gas exchange, heart rate, and blood lactate concentration variables were monitored in all tests. The values of all parameters at the v corresponding to MLSS, IAnT, VT, and HRT were similar (p ≤ 0.05), with high agreement (r > 0.400), except for carbon dioxide (V[Combining Dot Above]CO2) that was higher for MLSS compared with VT (p ≤ 0.05). However, the v at LT3.5 was higher when compared with other methods for v and bioenergetical factors. It is suggested that IAnT, VT, and HRT methods are better predictors of the intensity corresponding to the commonly accepted gold-standard method (i.e., MLSS) for the aerobic capacity evaluation compared with LT3.5.

Can the Critical Power Model Explain the Increased Peak Velocity/Power During Incremental Test After Concurrent Strength and Endurance Training?

Denadai, BS and Greco, CC. Can the critical power model explain the increased peak velocity/power during incremental test after concurrent strength and endurance training? J Strength Cond Res 31(8): 2319-2323, 2017-The highest exercise intensity that can be maintained at the end of a ramp or step incremental test (i.e., velocity or work rate at V[Combining Dot Above]O2max - Vpeak/Wpeak) can be used for endurance performance prediction and individualization of aerobic training. The interindividual variability in Vpeak/Wpeak has been attributed to exercise economy, anaerobic capacity, and neuromuscular capability, alongside the major determinant of aerobic capacity. Interestingly, findings after concurrent strength and endurance training performed by endurance athletes have challenged the actual contribution of these variables. The critical power model usually derived from the performance of constant-work rate exercise can also explain tolerance to a ramp incremental exercise so that, Vpeak/Wpeak can be predicted accurately. However, there is not yet discussion of possible concomitant improvements in the parameters of the critical power model and Vpeak/Wpeak after concurrent training and whether they can be associated with and therefore depend on different neuromuscular adaptations. Therefore, this brief review presents some evidence that the critical power model could explain the improvement of Vpeak/Wpeak and should be used to monitor aerobic performance enhancement after different concurrent strength- and endurance-training designs.

Endurance Performance during Severe-Intensity Intermittent Cycling: Effect of Exercise Duration and Recovery Type.

Slow component of oxygen uptake (VO2SC) kinetics and maximal oxygen uptake (VO2max) attainment seem to influence endurance performance during constant-work rate exercise (CWR) performed within the severe intensity domain. In this study, it was hypothesized that delaying the attainment of VO2max by reducing the rates at which VO2 increases with time (VO2SC kinetics) would improve the endurance performance during severe-intensity intermittent exercise performed with different work:recovery duration and recovery type in active individuals. After the estimation of the parameters of the VO2SC kinetics during CWR exercise, 18 males were divided into two groups (Passive and Active recovery) and performed at different days, two intermittent exercises to exhaustion (at 95% IVO2max, with work: recovery ratio of 2:1) with the duration of the repetitions calculated from the onset of the exercise to the beginning of the VO2SC (Short) or to the half duration of the VO2SC (Long). The active recovery was performed at 50% IVO2max. The endurance performance during intermittent exercises for the Passive (Short = 1523 ± 411; Long = 984 ± 260 s) and Active (Short = 902 ± 239; Long = 886 ± 254 s) groups was improved compared with CWR condition (Passive = 540 ± 116; Active = 489 ± 84 s). For Passive group, the endurance performance was significantly higher for Short than Long condition. However, no significant difference between Short and Long conditions was found for Active group. Additionally, the endurance performance during Short condition was higher for Passive than Active group. The VO2SC kinetics was significantly increased for CWR (Passive = 0.16 ± 0.04; Active = 0.16 ± 0.04 L.min-2) compared with Short (Passive = 0.01 ± 0.01; Active = 0.03 ± 0.04 L.min-2) and Long (Passive = 0.02 ± 0.01; Active = 0.01 ± 0.01 L.min-2) intermittent exercise conditions. No significant difference was found among the intermittent exercises. It can be concluded that the endurance performance is negatively influenced by active recovery only during shorter high-intensity intermittent exercise. Moreover, the improvement in endurance performance seems not be explained by differences in the VO2SC kinetics, since its values were similar among all intermittent exercise conditions.

Relationship Between Fatigue and Changes in Swim Technique During an Exhaustive Swim Exercise.

PURPOSE: To analyze the relationship between the responses of isometric peak torque (IPT) and maximal rate of force development (RFDmax) with the changes in stroking parameters in an exhaustive exercise performed in front crawl. METHODS: Fifteen male swimmers performed, on different days, the following protocols: maximal 400-m trial, strength tests before and after an exhaustive test at 100% of the mean speed obtained during the 400-m test, and the same procedures on day 2. RESULTS: The IPT of elbow flexors (79.9 ± 19.4 and 66.7 ± 20.0 N·m) and elbow extensors (95.1 ± 28.0 N·m and 85.8 ± 30.5 N·m) was decreased after the swim test, as was RFDmax (521.8 ± 198.6 and 426.0 ± 229.9 N·m/s; 420.6 ± 168.2 and 384.0 ± 143.5 N·m/s, respectively). Stroke length decreased during the swim test (1.96 ± 0.22 and 1.68 ± 0.29 m/stroke), while stroke rate increased (37.2 ± 3.14 and 41.3 ± 4.32 strokes/min). The propulsive phases increased while the nonpropulsive phases decreased during the test. Significant correlation was found between the changes in IPT and stroke length, stroke rate and recovery (elbow flexors), and entry and catch phase (elbow extensors). In addition, significant correlation was found between the changes in RFDmax of elbow flexors with the changes in pull and recovery phases. CONCLUSION: Changes in swim technique during an exhaustive test can be, at least in part, associated with fatigue of the arm muscles.

Prior heavy-intensity exercise's enhancement of oxygen-uptake kinetics and short-term high-intensity exercise performance independent of aerobic-training status.

UNLABELLED: Prior high-intensity exercise can improve exercise performance during severe-intensity exercise. These positive alterations have been attributed, at least in part, to enhancement of overall oxygen-uptake (VO2) kinetics. PURPOSE: To determine the effects of prior heavy-intensity exercise on VO2 kinetics and short-term high-intensity exercise performance in individuals with different aerobic-training statuses. METHODS: Fifteen active subjects (UT; VO2max = 43.8 ± 6.3 mL · kg-1 · min-1) and 10 well-trained endurance cyclists (T; VO2max = 66.7 ± 6.7 mL · kg-1 · min-1) performed the following protocols: an incremental test to determine lactate threshold and VO2max, 4 maximal constant-load tests to estimate critical power, and two 3-min bouts of cycle exercise, involving 2 min of constant-work-rate exercise at severe intensity followed by a 1-min all-out sprint test. This trial was performed without prior intervention and 10 min after prior heavy-intensity exercise (ie, 6 min at 90% critical power). RESULTS: The mean response time of VO2 was shortened after prior exercise for both UT (30.7 ± 9.2 vs 24.1 ± 7.2 s) and T (31.8 ± 5.2 vs 25.4 ± 4.3 s), but no group-by-condition interaction was detected. The end-sprint performance (ie, mean power output) was improved in both groups (UT ~4.7%, T ~2.0%; P < .05) by prior exercise. CONCLUSION: The effect of prior heavy-intensity exercise on overall VO2 kinetics and short-term high-intensity exercise performance is independent of aerobic-training status.

Reliability of cardiorespiratory parameters during cycling exercise performed at the severe domain in active individuals.

The purpose of this study was to determine the test-retest reliability of cardiorespiratory parameters during cycling exercise performed at severe domain in active individuals. Thirteen active males (24.5 ± 4.5 years) performed the following tests: (a) an incremental test to determine V[Combining Dot Above]O2max and the intensity associated with VO2max (IVO2max); and (b) 4 repetitions of square-wave transitions from rest to a power corresponding to 95% IVO2max to determine the parameters of VO2 kinetics and time to exhaustion (Tlim). Participants performed only 2 transitions on any given day. The interval between the 2 experimental sessions was 48-72 hours. The intraclass correlation coefficient (ICC) and typical error as the coefficient of variation were used to assess reliability. Although the 2 measures of Tlim were moderately related (ICC = 0.78; p < 0.01), Tlim from the second session (545.2 ± 103.1 seconds) was significantly higher than that of the first (492.5 ± 100.9 seconds; p = 0.02). Moderate to high reliability (ICC = 0.76-0.93) for the amplitudes of the VO2 kinetics responses was found. Poor reliability, however, was found for time constants and time delays of the VO2 kinetics responses. Thus, in nonfamiliarized individuals, Tlim shows a relatively low within-subject coefficient of variation. However, the second score in a series of 2 Tlim tests may be significantly greater than the first. We have also demonstrated that the amplitudes of the V[Combining Dot Above]O2 response have significantly moderate to high reliability. The time-based parameters, however, present an important day-to-day intraindividual variation. Therefore, several transitions are recommended to monitoring changes in an individual over any time frame.

How narrow is the spectrum of submaximal speeds in swimming?

The purpose of this study was to identify the boundary of submaximal speed zones (i.e., exercise intensity domains) between maximal aerobic speed (S-400) and lactate threshold (LT) in swimming. A 400-m all-out test, a 7 × 200 m incremental step test, and two to four 30-minute submaximal tests were performed by 12 male endurance swimmers (age = 24.5 ± 9.6 years; body mass = 71.3 ± 9.8 kg) to determine S-400, speed corresponding to LT, and maximal lactate steady state (MLSS). S-400 was 1.30 ± 0.09 m·s (400 m-5:08 minutes:seconds). The speed at LT (1.08 ± 0.02 m·s; 83.1 ± 2.2 %S-400) was lower than the speed at MLSS (1.14 ± 0.02 m·s; 87.5 ± 1.9 %S-400). Maximal lactate steady state occurred at 26 ± 10% of the difference between the speed at LT and S-400. Mean blood lactate values at the speeds corresponding to LT and MLSS were 2.45 ± 1.13 mmol·L and 4.30 ± 1.32 mmol·L, respectively. The present findings demonstrate that the range of intensity zones between LT and MLSS (i.e., heavy domain) and between MLSS and S-400 (i.e., severe domain) are very narrow in swimming with LT occurring at 83% S-400 in trained swimmers. Precision and sensitivity of the measurement of aerobic indexes (i.e., LT and MLSS) should be considered when conducting exercise training and testing in swimming.

Fatigue and rapid hamstring/quadriceps force capacity in professional soccer players.

The aim of this study was to investigate the effect of fatigue induced by an exhaustive laboratory-based soccer-specific exercise on different hamstrings/quadriceps (H:Q) ratios of soccer players. Twenty-two male professional soccer players (23·1 ± 3·4 year) performed maximal eccentric (ecc) and concentric (con) contractions for knee extensors (KE) and flexors (KF) at 60° s(-1) and 180° s(-1) to assess conventional (H(con) :Q(con)) and functional (H(ecc) :Q(con)) ratios. Additionally, they performed maximal voluntary isometric contraction for KE and KF, from which the maximal muscle strength, rate of force development (RFD) and RFD H:Q strength ratio (RFDH:Q) were extracted. Thereafter, subjects were performed an exhaustive laboratory-based soccer-specific exercise and a posttest similar to the pretest. There was significant reduction in H(con) :Q(con) (0·60 ± 0·06 versus 0·58 ± 0·06, P<0·05) and in H(ecc) :Q(con) (1·29 ± 0·2 versus 1·16 ± 0·2, P<0·01) after the soccer-specific exercise. However, no significant difference between Pre and Post exercise conditions was found for RFDH:Q at 0-50 (0·53 ± 0·23 versus 0·57 ± 0·24, P>0·05) and 0-100 ms (0·53 ± 0·17 versus 0·55 ± 0·17, P>0·05). In conclusion, H:Q strength ratios based on peak force values are more affected by fatigue than RFDH:Q obtained during early contraction phase. Thus, fatigue induced by soccer-specific intermittent protocol seems not reduce the potential for knee joint stabilization during the initial phase of voluntary muscle contraction.

Physiological and stroke parameters to assess aerobic capacity in swimming.

PURPOSE: To identify the speed corresponding to anaerobic threshold using the D-max method for both blood lactate and biomechanical stroke parameters determined in an incremental swimming test and to compare this information with the speed corresponding to the maximal lactate steady state (SMLSS). METHODS: Five male long-distance swimmers and 8 triathletes (N=13; age 23.8±9.5 y, height 1.76±0.1 m, weight 71.3±9.8 kg) performed the following protocols: maximal 400-m test to determine maximal aerobic speed (S400); 7×200-m incremental test to determine the speed corresponding to the D-max point on the blood lactate (SLa), stroke-rate (SSR), stroke-length (SSL), and stroke-index (SSI) responses; and two to four 30-min submaximal tests to determine the SMLSS. RESULTS: SLA (1.18±0.08 m/s), SSI (1.18±0.08 m/s), SSR (1.17±0.1 m/s), and SSL (1.16±0.09 m/s) were not significantly different from each other or from SMLSS (1.13±0.08 m/s). There were high correlations between SLA, SSI, SSR, SSL, and SMLSS (r=.91, .89, .85, and .80, respectively). The typical errors of estimate for SLA (3.2%), SSI (3.7%), SSR (4.1%), and SSL (4.7%) suggest good validity of these variables to predict SMLSS. Furthermore, all physiological and biomechanical variables were moderately to highly correlated with S400 (r=.73-.95). CONCLUSIONS: It is possible to obtain a physiological index of aerobic capacity and performance using simple biomechanical measurements during an incremental test without performing blood lactate analyses.

Rapid hamstrings/quadriceps strength capacity in professional soccer players with different conventional isokinetic muscle strength ratios.

Muscle strength imbalance can be an important factor in hamstrings muscle strain. A hamstrings/quadriceps (H/Q) strength ratio based on concentric peak torque values (Hcon:Qcon) has traditionally been used to describe the potential for knee-joint destabilization. Because certain standard actions in soccer are explosive, the analysis of the H/Q strength ratio based on the rate of torque development (Hrtd:Qrtd) might also be useful in the evaluation of joint stability. The objective of this study was to compare the Hrtd:Qrtd between professional soccer players with heterogeneous values of Hcon:Qcon. Thirty-nine professional soccer players took part in the following procedures on different days: 1) Familiarization session with the isokinetic dynamometer, and 2) Two maximal isometric actions and five maximal concentric actions at 60°·s(-1) for hamstrings (H) and quadriceps (Q). Participants were ranked according to their Hcon:Qcon ratio. The median third was excluded to form a high torque group (HTG), and a low torque group (LTG). Peak isometric (H) and concentric (H and Q) torques and rate of torque development (H) were significantly greater in the HTG group. Similarly, Hcon:Qcon (0.68 ± 0.02 vs. 0.52 ± 0.03) and Hrtd:Qrtd (0.54 ± 0.12 vs. 0.43 ± 0.16) were significantly greater in the HTG group than in the LTG group. There was no significant correlation between Hcon:Qcon and Hrtd:Qrtd. It can be concluded that Hcon:Qcon and Hrtd:Qrtd are determined, but not fully defined, by shared putative physiological mechanisms. Thus, the physiologic and clinical significance of Hcon:Qcon and Hrtd:Qrtd to an athlete's individual evaluation might be different. Key pointsSoccer players with high (0.66-0.70) and low (0.50-0.54) conventional concentric hamstrings:quadriceps ratios (Hcon:Qcon) tend to demonstrate similar profiles (i.e., high and low, respectively) in their rate of the torque development H/Q ratio (Hrtd:Qrtd).The lack of a significant relationship between Hcon:Qcon and Hrtd:Qrtd suggests that these ratios are determined, but not fully defined, by shared putative physiological mechanisms.Preseason screening programs that monitor hamstrings:quadriceps ratios should recognize that the physiologic and clinical significance of Hcon:Qcon and Hrfd:Qrfd to an athlete's individual evaluation might be different.

Improvements in metabolic and neuromuscular fitness after 12-week bodypump® training.

Greco, CC, Oliveira, AS, Pereira, MP, Figueira, TR, Ruas, VD, Gonçalves, M, and Denadai, BS. Improvements in metabolic and neuromuscular fitness after 12-week Bodypump® training. J Strength Cond Res 25(12): 3422-3431, 2011-The purpose of this study was to evaluate the effects of a 12-week group fitness training program (Bodypump®) on anthropometry, muscle strength, and aerobic fitness. Nineteen women (21.4 ± 2.0 years old) were randomly assigned to a training group (n = 9) and to a control group (n = 10). We show that this training program improved the 1 repetition maximum squats by 33.1% (p < 0.001) and the maximal isometric voluntary contraction (MVC) by 13.6% (p < 0.05). Additionally, decreases in knee extensor electromyographic activity during the MVC (30%, p < 0.01) and during the squats (15%, p < 0.05) and lunges of a simulated Bodypump® session were observed after the training. Concomitantly, blood lactate and heart rate after squats of a simulated Bodypump® session were decreased by 33 and 7% (p < 0.05), respectively. Body mass, body fat, and the running velocity at the onset of blood lactate accumulation did not change significantly in response to this training program. We conclude that Bodypump® training improves muscular strength and decreases metabolic stress during lower limb exercises. However, no significant improvements in running aerobic fitness nor in body mass and body fat were observed. Practitioners of Bodypump® training may benefit from the increased muscular strength and the decreased muscular fatigability during exercise tasks whose motor patterns are related to those involved in this training program. However, these functional gains do not seem to be transferable into running aerobic fitness.

Maximal lactate steady-state independent of recovery period during intermittent protocol.

Barbosa, LF, de Souza, MR, Corrêa Caritá, RA, Caputo, F, Denadai, BS, and Greco, CC. Maximal lactate steady-state independent of recovery period during intermittent protocol. J Strength Cond Res 25(12): 3385-3390, 2011-The purpose of this study was to analyze the effect of the measurement time for blood lactate concentration ([La]) determination on [La] (maximal lactate steady state [MLSS]) and workload (MLSS during intermittent protocols [MLSSwi]) at maximal lactate steady state determined using intermittent protocols. Nineteen trained male cyclists were divided into 2 groups, for the determination of MLSSwi using passive (VO(2)max = 58.1 ± 3.5 ml·kg·min; N = 9) or active recovery (VO(2)max = 60.3 ± 9.0 ml·kg·min; N = 10). They performed the following tests, in different days, on a cycle ergometer: (a) Incremental test until exhaustion to determine (VO(2)max and (b) 30-minute intermittent constant-workload tests (7 × 4 and 1 × 2 minutes, with 2-minute recovery) to determine MLSSwi and MLSS. Each group performed the intermittent tests with passive or active recovery. The MLSSwi was defined as the highest workload at which [La] increased by no more than 1 mmol·L between minutes 10 and 30 (T1) or minutes 14 and 44 (T2) of the protocol. The MLSS (Passive-T1: 5.89 ± 1.41 vs. T2: 5.61 ± 1.78 mmol·L) and MLSSwi (Passive-T1: 294.5 ± 31.8 vs. T2: 294.7 ± 32.2 W; Active-T1: 304.6 ± 23.0 vs. T2: 300.5 ± 23.9 W) were similar for both criteria. However, MLSS was lower in T2 (4.91 ± 1.91 mmol·L) when compared with in T1 (5.62 ± 1.83 mmol·L) using active recovery. We can conclude that the MLSSwi (passive and active conditions) was unchanged whether recovery periods were considered (T1) or not (T2) for the interpretation of [La] kinetics. In contrast, MLSS was lowered when considering the active recovery periods (T2). Thus, shorter intermittent protocols (i.e., T1) to determine MLSSwi may optimize time of the aerobic capacity evaluation of well-trained cyclists.

Stroke phases responses around maximal lactate steady state in front crawl.

The objective of this study was to analyze changes in stroke rate (SR), stroke length (SL) and stroke phases (entry and catch, pull, push and recovery) when swimming at (MLSS) and above (102.5% MLSS) the maximal lactate steady state. Twelve endurance swimmers (21±8 year, 1.77±0.10 m and 71.6±7.7 kg) performed in different days the following tests: (1) 200- and 400-m all-out tests, to determine critical speed (CS), and; (2) 2-4 30-min sub-maximal constant-speed tests, to determine the MLSS and 102.5% MLSS. There was significant difference among MLSS (1.22±0.05 ms(-1)), 102.5% MLSS (1.25±0.04 ms(-1)) and CS (1.30±0.08 ms(-1)). SR and SL were maintained between the 10th and 30th minute of the test swum at MLSS and have modified significantly at 102.5% MLSS (SR - 30.9±3.4 and 32.2±3.5 cycles min(-1) and SL - 2.47±0.2 and 2.38±0.2 m cycle(-1), respectively). All stroke phases were maintained at 10th and 30th minute at MLSS. However, the relative duration of propulsive phase B (pull) increased significantly at 102.5% MLSS (21.7±3.4% and 22.9±3.9%, respectively). Therefore, the metabolic condition may influence the stroke parameters (SR and SL) and stroke strategy to maintain the speed during swim tests lasting 30 min.

Effects of exercise mode on the oxygen uptake kinetic response to severe-intensity exercise in prepubertal children.

The objective of this study was to verify the effect of the exercise mode on slow component of VO2 (VO2SC) in children aged 11-12 years during severe-intensity exercise. After determination of the lactate threshold (LT) and peak VO2 (VO2peak) in both cycling (CE) and running exercise (TR), fourteen active boys completed a series of "square-wave" transitions of 6-min duration at 75 delta [75% delta = LT + 0.75 3 (VO2peak--LT)] to determine the VO2 kinetics. The VO2SC was significantly higher in CE (180.5 +/- 155.8 ml x min-1) than in TR (113.0 +/- 84.2 ml x min-1). We can conclude that, although a VO2SC does indeed develop during TR in children, its magnitude is considerably lower than in CE during severe-intensity exercise.

Effects of gender on stroke rates, critical speed and velocity of a 30-min swim in young swimmers.

Our objective was to analyze the effect of gender on the relationship between stroke rates corresponding to critical speed (SRCS) and maximal speed of 30 min (SRS30) in young swimmers. Twenty two males (GM1) (Age = 15.4 ± 2.1 yr., Body mass = 63.7 ± 12.9 kg, Stature = 1.73 ± 0.09 m) and fourteen female (GF) swimmers (Age = 15.1 ± 1.6 yr., Body mass = 58.3 ± 8.8 kg, Stature = 1.65 ± 0.06 m) were studied. A subset of males (GM2) was matched to the GF by their velocity for a 30 min swim (S30). The critical speed (CS) was determined through the slope of the linear regression line between the distances (200 and 400 m) and participant's respective times. CS was significantly higher than S30 in males (GM1 - 1.25 and 1.16 and GM2 - 1.21 and 1.12 m·s(-1)) and females (GF - 1.15 and 1.11 m·s(-1)). There was no significant difference between SRCS and SRS30 in males (GM1 - 34.16 and 32.32 and GM2 - 34.67 and 32.46 cycle·s(-1), respectively) and females (GF - 34.18 and 33.67 cycle·s(-1), respectively). There was a significant correlation between CS and S30 (GM1 - r = 0.89, GF - r = 0.94 and GM2 - r = 0.90) and between SRCS and SRS30 (GM1 - r = 0.89, GF - r = 0.80 and GM2 - r = 0.88). Thus, the relationship between SRCS and SRS30 is not influenced by gender, in swimmers with similar and different aerobic capacity levels. Key pointsThe main finding of this study was that the relationship between SRCS and SRS30, which is not dependent on gender, in swimmers with similar and different aerobic capacity levels.In swimmers who had different S30 values, CS was higher than S30 in boys and girls, and CS and S30 were higher in boys than girls, but SRCS and SRS30 were similar between genders.In swimmers who had similar S30 values, CS was higher than S30 in boys and girls. However, boys still presented higher values of CS than girls. SRCS was higher than SRS30 in boys, but these variables were similar in girls. SRCS and SRS30 were similar between genders.Girls presented lower submaximal blood lactate levels than boys.

Interval training at 95% and 100% of the velocity at VO2 max: effects on aerobic physiological indexes and running performance.

The objective of this study was to analyze the effect of two different high-intensity interval training (HIT) programs on selected aerobic physiological indices and 1500 and 5000 m running performance in well-trained runners. The following tests were completed (n=17): (i) incremental treadmill test to determine maximal oxygen uptake (VO2 max), running velocity associated with VO2 max (vVO2 max), and the velocity corresponding to 3.5 mmol/L of blood lactate concentration (vOBLA); (ii) submaximal constant-intensity test to determine running economy (RE); and (iii) 1500 and 5000 m time trials on a 400 m track. Runners were then randomized into 95% vVO2 max or 100% vVO2 max groups, and undertook a 4 week training program consisting of 2 HIT sessions (performed at 95% or 100% vVO2 max, respectively) and 4 submaximal run sessions per week. Runners were retested on all parameters at the completion of the training program. The VO2 max values were not different after training for both groups. There was a significant increase in post-training vVO2 max, RE, and 1500 m running performance in the 100% vVO2 max group. The vOBLA and 5000 m running performance were significantly higher after the training period for both groups. We conclude that vOBLA and 5000 m running performance can be significantly improved in well-trained runners using a 4 week training program consisting of 2 HIT sessions (performed at 95% or 100% vVO2 max) and 4 submaximal run sessions per week. However, the improvement in vVO2 max, RE, and 1500 m running performance seems to be dependent on the HIT program at 100% vVO2 max.