Blood lactate and stroke parameters during front crawl in elite swimmers with disability

The purpose of this investigation was to compare the blood lactate concentration ([La]), stroke distance (D(s)), and swim index (SI) during an incremental swim test (IST) in elite swimmers who had a loss in mobility (LM) (n = 6) or who had full mobility (FM) (n = 5) of the lower limbs. The IST consisted of 5 repeats of either 100 or 200 m front crawl depending upon the ability level of the swimmer. The [La] and heart rate measured during the IST showed no significant differences (p > 0.05). However, velocity (V(s)) and D(s) were all significantly lower (p < 0.01) during the IST. SI was significantly (p < 0.01) lower during repeats 1 to 3 and 5, but not repeat 4. These data indicate that the [La] response to incremental exercise is similar during incremental front crawl activity in swimmers suffering from loss of lower limb mobility. However, a critical V(s) is reached in LM swimmers where swimming efficiency is optimal compared with FM swimmers.     

Inspiratory muscle fatigue after race-paced swimming is not restricted to the front crawl stroke

ABSTRACT: Lomax, M, Iggleden, C, Tourell, A, Castle, S, and Honey, J. Inspiratory muscle fatigue following race-paced swimming is not restricted to the front crawl stroke. J Strength Cond Res 26(10): 2729-2733, 2012-The occurrence of inspiratory muscle fatigue (IMF) has been documented after front crawl (FC) swimming of various distances. Whether IMF occurs after other competitive swimming strokes is not known. The aim of the present study was to assess the impact of all 4 competitive swimming strokes on the occurrence of IMF after race-paced swimming and to determine whether the magnitude of IMF was related to the breathing pattern adopted and hence breathing frequency (fb). Eleven, nationally ranked, youth swimmers completed four 200-m swims (one in each competitive stroke) on separate occasions. The order of the swims, which consisted of FC, backstroke (BK), breaststroke (BR), and butterfly (FLY), was randomized. Maximal inspiratory mouth pressure (MIP) was assessed before (after a swimming and inspiratory muscle warm-up) and after each swim with fb calculated post swim from recorded data. Inspiratory muscle fatigue was evident after each 200-m swim (p < 0.05) but did not differ between the 4 strokes (range 18-21%). No relationship (p > 0.05) was observed between fb and the change in MIP (FC: r = -0.456; BK: r = 0.218; BR: r = 0.218; and FLY: r = 0.312). These results demonstrate that IMF occurs in response to 200-m race-paced swimming in all strokes and that the magnitude of IMF is similar between strokes when breathing is ad libitum occurring no less than 1 breath (inhalation) every third stroke.     

Rolling rhythms in front crawl swimming with six-beat kick

The purpose of this study was to establish the rhythm characteristics of skilled front crawl swimmers using a six-beat kick. These included the amplitudes of the first three Fourier harmonics (H1, H2, H3) and their percent contributions to power contained in the angular displacement signals of the shoulders, hips, knees, and ankles with respect to the longitudinal axis in line with the swimming direction. Three-dimensional video data of seven national/international level swimmers were collected during simulated 200 m front crawl races in which swimmers maintained six-beat kicking patterns. Swimmers differed in all variables but had small variability across the four 50 m laps. Modest changes occurred during the 200 m, with the exception of shoulder roll, which remained constant and was represented almost entirely by a single sinusoid (H1). Changes across laps reached significance for swimming speed, stroke rate, hip roll, and H3 wave velocity between the knee and ankle. A H3 body wave of moderate and increasing velocity travelled caudally from hip to ankle. In the light of existing knowledge of aquatic locomotion this was compatible with the goal of generating propulsion in an efficient manner.     

Intra-Individual Variability of Surface Electromyography in Front Crawl Swimming

The variability of electromyographic (EMG) recordings between and within participants is a complex problem, rarely studied in swimming. The importance of signal normalization has long been recognized, but the method used might influence variability. The aims of this study were to: (i) assess the intra-individual variability of the EMG signal in highly skilled front crawl swimmers, (ii) determine the influence of two methods of both amplitude and time normalization of the EMG signal on intra-individual variability and of time normalization on muscle activity level and (iii) describe the muscle activity, normalized using MVIC, in relation to upper limb crawl stroke movements. Muscle activity of rectus abdominis and deltoideus medialis was recorded using wireless surface EMG in 15 adult male competitive swimmers during three trials of 12.5 m front crawl at maximal speed without breathing. Two full upper limb cycles were analyzed from each of the swimming trials, resulting in six full cycles used for the intra-individual variability assessment, quantified with the coefficient of variation (CV), coefficient of quartile variation (CQV) and the variance ratio (VR). The results of this study support previous findings on EMG patterns of deltoideus medialis and rectus abdominis as prime mover during the recovery (45% activity relative to MVIC), and stabilizer of the trunk during the pull (14.5% activity) respectively. The intra-individual variability was lower (VR of 0.34–0.47) when compared to other cyclic movements. No meaningful differences were found between variability measures CV or VR when applying either of the amplitude or the time normalization methods. In addition to reporting the mean amplitude and standard deviation, future EMG studies in swimming should also report the intra-individual variability, preferably using VR as it is independent of peak amplitude, provides a good measure of repeatability and is insensitive to mean EMG amplitude and the degree of smoothing applied.     

Effect of velocity and added resistance on selected coordination and force parameters in front crawl

The effect of (a) increasing velocity and (b) added resistance was examined on the stroke (stroke length, stroke rate [SR]), coordination (index of coordination [IdC], propulsive phases), and force (impulse and peaks) parameters of 7 national-level front crawl swimmers (17.14 ± 2.73 years of swimming; 57.67 ± 1.62 seconds in the 100-m freestyle). The additional resistance was provided by a specially designed parachute. Parachute swimming (PA) and free-swimming (F) conditions were compared at 5 velocities per condition. Video footage was used to calculate the stroke and coordination parameters, and sensors allowed the determination of force parameters. The results showed that (a) an increase in velocity (V) led to increases in SR, IdC, propulsive phase duration, and peak propulsive force (p < 0.05), but no significant change in force impulse per cycle, whatever the condition (PA or F); and (b) in PA conditions, significant increases in the IdC, propulsive phase duration, and force impulse and a decrease in SR were recorded at high velocities (p < 0.05). These results indicated that, in the F condition, swimmers adapted to the change in velocity by modifying stroke and coordination rather than force parameters, whereas the PA condition enhanced the continuity of propulsive action and force development. Added resistance, that is, "parachute training," can be used for specific strength training purposes as long as swimming is performed near maximum velocity.     

Effects of a 6-week plyometric training program on performances in pubescent swimmers

This study examined in pubescent swimmers the effects on front crawl performances of a 6-week plyometric training (PT) in addition to the habitual swimming program. Swimmers were assigned to a control group (n = 11, age: 14.1 ± 0.2 years; G(CONT)) and a combined swimming and plyometric group (n = 12, age: 14.3 ± 0.2 years; GSP), both groups swimming 5.5 h · wk(-1) during a 6-week preseason training block. In the GSP, PT consisted of long, lateral high and depth jumps before swimming training 2 times per week. Pre and posttests were performed by jump tests (squat jump [SJ], countermovement jump [CMJ]) and swim tests: a gliding task, 400- and 50-m front crawl with a diving start (V400 and V50, m · s(-1)), and 2 tests with a water start without push-off on the wall (25 m in front crawl and 25 m only with kicks). Results showed improvement only for GSP for jump tests (Δ = 4.67 ± 3.49 cm; Δ = 3.24 ± 3.17 cm; for CMJ and SJ, respectively; p < 0.05) and front crawl tests (Δ = 0.04 ± 0.04 m · s(-1); Δ = 0.04 ± 0.05 m · s(-1); for V50 and V400, respectively; p < 0.05). Significant correlations were found for GSP between improvements in SJ and V50 (R = 0.73, p < 0.05). Results suggested a positive effect of PT on specific swimming tasks such as dive or turn but not in kicking propulsion. Because of the practical setup of the PT and the relevancy of successful starts and turns in swimming performances, it is strongly suggested to incorporate PT in pubescent swimmers' training and control it by jump performances.     

Blood lactate and metabolic responses to controlled frequency breathing during graded swimming

Controlled frequency breathing (CFB) is a training technique used by swimmers in an effort to simulate high-intensity workloads by limiting oxygen availability to the body and stimulating anaerobic metabolism. During CFB, a swimmer voluntarily restricts breathing, which, theoretically, limits oxygen availability and stimulates anaerobic metabolism. The purpose of this study was to determine the influence of CFB on blood lactate and metabolic responses during graded increases in swimming intensity. A free swimming (FS) protocol was used to determine blood lactate and heart rate (HR) responses to CFB, while a tethered swimming (TS) protocol was used to determine blood lactate, HR, and ventilatory responses to CFB. The subjects swam four 3-minute trials at workloads of 55, 65, 75, and 85% of peak intensity during both protocols. A total of 46 competitive collegiate swimmers participated in the study. Thirty-four subjects (14 men and 20 women) completed the FS protocol, and 12 subjects (7 men and 5 women) completed the TS protocol. CFB reduced ventilation and Vo(2) (p < 0.05) during the TS protocol and reduced HR (p < 0.05) during the FS protocol when compared to normal breathing. However, CFB did not alter blood lactate concentrations for either protocol (p > 0.05). Our findings demonstrate that although CFB does not alter the blood lactate response to graded increases in swimming intensity, it appears to reduce the ventilatory and HR responses to exercise. Thus, swim coaches can use CFB at moderate intensities to simulate high-intensity training but should consider adjusting HR training zones to reflect the reduction in HR associated with reduced ventilation.     

Active drag related to velocity in male and female swimmers

Propulsive arm forces of 32 male and 9 female swimmers were measured during front crawl swimming using arms only, in a velocity range between 1.0 m s-1 and 1.8 m s-1. At constant velocity, the measured mean propulsive force Fp equals the mean active drag force (Fd). It was found that Fd is related to the swimming velocity v raised to the power 2.12 +/- 0.20 (males) or 2.28 +/- 0.35 (females). Although many subjects showed rather constant values of Fd/v2, 12 subjects gave significantly (p less than 0.01) stronger or weaker quadratic relationships. Differences in drag force and coefficient of drag between males and females (drag: 28.9 +/- 5.1 N, 20.4 +/- 1.9 N, drag coefficient: 0.64 +/- 0.09, 0.54 +/- 0.07 respectively) are especially apparent at the lowest swimming velocity (1 m s-1), which become less at higher swimming velocities. Possible explanations for the deviation of the power of the velocity from the ideal quadratic dependency are discussed.     

Effect of body roll amplitude and arm rotation speed on propulsion of arm amputee swimmers

Only a limited amount of research has gone into evaluating the contribution made by the upper arm to the propulsion of elite swimmers with an amputation at elbow level. With assistance of computational fluid dynamics (CFD) modelling, the swimming technique of competitive arm amputee swimmers can be assessed through numerical simulations which test the effect of various parameters on the effectiveness of the swimming propulsion.This numerical study investigates the effect of body roll amplitude and of upper arm rotation speed on the propulsion of an arm amputee swimmer, at different mean swimming speeds. Various test cases are simulated resulting in a thorough analysis of the complex body/fluid interaction with a detailed quantitative assessment of the effect of the variation of each parameter on the arm propulsion. It is found that a body roll movement with an amplitude of 45° enhances greatly the propulsive contribution from the upper arm with an increase of about 70% in the propulsive force compared to the no roll condition. An increase in the angular velocity of the upper arm also leads to a concomitant increase in the propulsive forces produced by the arm.Such results have direct implications for competitive arm amputee front crawl swimmers and for those who coach them. One important message that emerges in this present work is that there exists, for any given swimming speed, a minimum angular velocity at which the upper arm must be rotated to generate effective propulsion. Below this velocity, the upper arm will experience a net resistive drag force which adversely affects swimming performance.     

Effect of wearing clothes on oxygen uptake and ratings of perceived exertion while swimming

For a comparative study between swimming in swimwear (control-sw) and swimming in clothes (clothes-sw), oxygen uptake (VO2) and ratings of perceived exertion (RPE) were measured. The subjects were six male members of a university swimming team. Three swimming strokes--the breaststroke, the front crawl stroke and the elementary backstroke--were applied. With regards to clothes-sw, swimmers wore T-shirts, sportswear (shirt and pants) over swimwear and running shoes. In both cases of control-sw and clothes-sw, the VO2 was increased exponentially with increased swimming speed. The VO2 of the subjects during the clothed tests did not exceed 1.4 times of that in the case of control-sw at swimming speeds below 0.3 m/s. As swimming speeds increased, VO2 difference in both cases increased. Consequently, VO2 in the clothed tests was equal to 1.5-1.6 times and 1.5-1.8 times of that in the swimwear tests at speeds of 0.5 and 0.7 m/s, respectively. At speeds below 0.6 m/s in clothes-sw, the breaststroke showed lower VO2 than the front crawl stroke, and the elementary backstroke showed higher VO2 than the other two swimming strokes. RPE increased linearly with %peak VO2. In addition, any RPE differences among the three swimming strokes were not shown in the control-sw tests. At an exercise intensity above 60 %peak VO2, clothed swimmers showed slightly higher RPE in the front crawl stroke compared to that in the two other swimming strokes.     

Effect of breathing pattern on arm coordination symmetry in front crawl

This study analyzed the relationship between breathing pattern and arm coordination symmetry in 11 expert male swimmers who performed the front crawl at their 100-m race pace using seven randomized breathing patterns. Two indexes of coordination (IdCP and IdCNP) and a symmetry index (SI) based on the difference of IdCP - IdCNP were calculated. IdCP calculated the lag time between the beginning of arm propulsion on the nonpreferential breathing side and the end of arm propulsion on the preferential breathing side; IdCNP did the converse. The IdCP and IdCNP comparisons and the SI showed coordination asymmetries among the seven breathing patterns. Specifically, breathing to the preferential side led to an asymmetry, in contrast to the other breathing patterns, and the asymmetry was even greater when the swimmer breathed to his nonpreferential side. These findings highlight the effect of breathing laterality in that coordination was symmetric in patterns with breathing that was bilateral, axed (as in breathing with a frontal snorkel), or removed (as in apnea). One practical application is that arm coordination asymmetry can be prevented or reduced by using breathing patterns that balance the coordination.     

Assisted and resisted sprint training in swimming

This study was undertaken to determine whether the resisted-sprint in overstrength (OSt) or the assisted-sprint in overspeed (OSp) could be efficient training methods to increase 100-m front crawl performance. Thirty-seven (16 men, 21 women) competition-level swimmers (mean +/- SD: age 17.5 +/- 3.5 years, height 173 +/- 14 cm, weight 63 +/- 14 kg) were randomly divided into 3 groups: OSt, OSp, and control (C). All swimmers trained 6 days per week for 3 weeks, including 3 resisted or assisted training sessions per week for the groups OSt and OSp respectively. Elastic tubes were used to generate swimming overstrength and overspeed. Three 100-m events were performed before, during, and after the training period. Before each 100-m event, strength of the elbow flexors and extensors was measured with an isokinetic dynamometer. Stroke rate and stroke length were evaluated using the video-recorded 100-m events. In the OSt group, elbow extensor strength, swimming velocity, and stroke rate significantly increased (p < 0.05), while stroke length remained unchanged after the 3-week training period. In the OSp group, stroke rate significantly increased (p < 0.05) and stroke length significantly decreased (p < 0.05) without changes in swimming velocity. No significant variations in the C group were observed. Both OSt and OSp proved to be more efficient than the traditional training program. However, the OSt training program had a larger impact on muscle strength, swimming performance, and stroke technique than the OSp program.     

Markerless analysis of front crawl swimming

Research on motion analysis of swimmers is commonly based on video recordings of the subject's motion, which are analyzed by manual digitization of feature points by an operator. This procedure has two main drawbacks: it is time-consuming, and it is affected by low repeatability. Therefore, the application of video-based, automatic approaches to motion analysis was investigated. A video-based, markerless system for the analysis of arm movements during front crawl swimming was developed. The method proposed by Corazza et al. (2010) was modified in order to be used into water environment. Three dimensional coordinates of shoulder, elbow and wrist joints centers of 5 sprint swimmers performing front crawl swimming were determined. Wrist joint velocity was also calculated. Accuracy and reliability of the proposed technique were evaluated by means of comparison with traditional manual digitization (SIMI Reality Motion Systems GmbH). Root mean square distance (RMSD) values between trajectories estimated with the two techniques were determined. Results show good accuracy for wrist joint (RMSD<56mm), and reliability, evaluated on one subject, comparable to the inter-operator variability associated with the manual digitization procedure. The proposed technique is therefore very promising for quantitative, wide-scale studies on swimmers' motion.     

Inter-individual variability and pattern recognition of surface electromyography in front crawl swimming

Variability of electromyographic (EMG) recordings is a complex phenomenon rarely examined in swimming. Our purposes were to investigate inter-individual variability in muscle activation patterns during front crawl swimming and assess if there were clusters of sub patterns present. Bilateral muscle activity of rectus abdominis (RA) and deltoideus medialis (DM) was recorded using wireless surface EMG in 15 adult male competitive swimmers. The amplitude of the median EMG trial of six upper arm movement cycles was used for the inter-individual variability assessment, quantified with the coefficient of variation, coefficient of quartile variation, the variance ratio and mean deviation. Key features were selected based on qualitative and quantitative classification strategies to enter in a k-means cluster analysis to examine the presence of strong sub patterns. Such strong sub patterns were found when clustering in two, three and four clusters. Inter-individual variability in a group of highly skilled swimmers was higher compared to other cyclic movements which is in contrast to what has been reported in the previous 50 years of EMG research in swimming. This leads to the conclusion that coaches should be careful in using overall reference EMG information to enhance the individual swimming technique of their athletes.     

Sodium bicarbonate ingestion improves performance in interval swimming

In an effort to determine the effects of bicarbonate (NaHCO3) ingestion on exercise performance, ten male college swimmers were studied during five different trials. Each trial consisted of five 91.4 m (100-yd) front crawl swims with a two-minute rest interval between each bout. The trials consisted of two NaHCO3 treatments, two placebo trials and one test with no-drink. One hour before the onset of swimming, the subjects were given 300 ml of citric acid flavored solution containing either 17 mmol of NaCl (placebo) or 2.9 mmol of NaHCO3.kg-1 body weight (experimental), or received no drink (no-drink). Performance times for each 91.4 m swim were recorded. Blood samples were obtained before and one hr after treatment, two min after warmup, and two min after the final 91.4 m sprint. Blood pH, lactate, standard bicarbonate (SBC) and base excess (BE) were measured. No differences were found for performance or the blood measurements between the placebo and no-drink trials. Bicarbonate feedings, on the other hand, produced a significant (P less than 0.05) improvement in performance on the fourth and fifth swimming sprints. Blood lactate, pH, SBC and BE were significantly higher (P less than 0.05) at post-exercise in NaHCO3 treatments. These data are in agreement with previous findings that during repeated bouts of exercise pre-exercise administration of NaHCO3 improves performance, possibly by facilitating the efflux of hydrogen ions from working muscles and thereby delaying the onset of fatigue.     

Buoyancy is the primary source of generating bodyroll in front-crawl swimming

The present study was conducted to determine the contribution of the turning effect of buoyant force for generating bodyroll and its relationship with the subjects' variability in swimming speed at distance pace and sub-maximal sprinting pace. The performances of front crawl swimming performed by 11 skilled swimmers were recorded with two panning periscopes for three-dimensional analysis. The bodyroll (BR) exhibited by each of the 11 male competitive swimmers was determined for every given instant as the time-integral of the conceptual angular velocity of the entire body about the long-axis, which was computed from the angular momentum and the moment of inertia of entire body. The part of BR generated by the buoyancy torque (BR(BT)) was determined from the moment of inertia of the entire body and the double time-integral of the buoyancy torque. The mean value for the peak-to-peak amplitude of the buoyancy torque was 15 Nm at distance pace and 19 Nm at sub-maximum sprinting speed. The contribution of buoyancy to BR was significantly greater ( P < 0.01) than that of the hydrodynamic forces. The individual swimming speed at sub-maximal sprinting pace was positively correlated ( P < 0.04) with the contribution of buoyancy to BR. These results showed that the skilled swimmers used buoyant force as the primary source of generating BR, and that faster swimmers used buoyant force more effectively to generate BR than slower swimmers. Based on the results and subsequent theoretical analysis, possible patterns of arm-BR coordination that may increase the effectiveness of using buoyant force for BR are discussed.     

Inspiratory muscle fatigue significantly affects breathing frequency, stroke rate, and stroke length during 200-m front-crawl swimming

The aim of the current study was to assess the impact of inspiratory muscle fatigue (IMF) on total breaths taken (f(tot)), breaths per minute (f(b)), stroke count (SC), stroke rate (SR), and stroke length (SL) during constant velocity front-crawl swimming. Eight collegiate swimmers undertook a 200-m front-crawl swim on 2 separate occasions. On 1 occasion, IMF was induced immediately before the swim (IMF trial), and on the other occasion, the swim was undertaken in the absence of IMF (control trial). Trials were administered using a randomized crossover design and at a swimming velocity equivalent to 85% of race pace: Pilot testing identified this as being the fastest pace, which did not induce IMF. Maximal inspiratory mouth pressure, which was measured at the mouth and from residual volume, fell by 17% (p < 0.05) in response to IMF but was unchanged in response to the swim itself (p < 0.05). When compared to the control trial, f(tot), f(b), SC, and SR increased (p < 0.05) and SL decreased (p < 0.05) in response to IMF. These data suggest that the increase in f(tot) and f(b) in the presence of IMF occurred, in part, in an attempt to alleviate dyspnea. As a result, SL decreased and SR and SC increased, although variability in the SR and SC response did occur. However, as a number of identical muscles are recruited during deep inspirations and the front-crawl arm stroke, the possibility that arm coordination was changed, in part, to compensate for a reduced force-generating capacity per arm stroke should not be overlooked.     

Estimation of hand forces and propelling efficiency during front crawl swimming with hand paddles

The aim of the study was to investigate possible modifications caused by hand paddles in the relative contribution of the lift and drag forces of the hand and in the propelling efficiency, during front crawl swimming. Eight female swimmers swam 25 m with maximal intensity without paddles, with small (116 cm(2)) and with large paddles (268 cm(2)). Four cameras operating at 60 Hz were used to record the images and the Ariel Performance Analysis System was used for the digitisation. The results showed that, although during swimming with hand paddles the hand's velocity decreased, the greater propulsive area of the hand paddle caused an increase in the drag, lift, resultant and effective forces of the hand. However, the relative contribution of lift and drag forces on swimming propulsion was not modified, nor was the direction of the resultant force. Hand paddles also increased the propelling efficiency, the stroke length and the swimming velocity, mainly because of the larger propulsive areas of the hand in comparison with free swimming. However, the significant decrease of the stroke rate, might argue the effectiveness of hand paddle training, particularly when large paddles are used in front crawl swimming.     

KINEMATIC VARIABLES AND BLOOD ACID-BASE STATUS IN THE ANALYSIS OF COLLEGIATE SWIMMERS’ ANAEROBIC CAPACITY

Short duration repeated maximal efforts are often used in swimming training to improve lactate tolerance, which gives swimmers the ability to maintain a high work rate for a longer period of time. The aim of the study was to examine the kinematics of swimming and its relation to the changes in blood acid-base status and potassium level. Seven collegiate swimmers, with at least 6 years of training experience, volunteered to participate in the study. The test consisted of 8 x 25 m front crawl performed with maximum effort. The rest period between repetitions was set to five seconds. Blood samples were taken from the fingertip at rest, after warm-up and in the 3rd minute after completion of the test. The swimming was recorded with a video recorder, for later analysis of time, velocity and technique (stroke index). Based on the swimming velocity results, the obtained curve can be divided into rapid decrease of velocity and relatively stable velocities. The breaking point of repetition in swimming velocity was assumed as the swimming velocity threshold and it was highly correlated with the decrease of the blood acid-base status (pH r=0.82, BE r=0.87, HCO₃ ^- r=0.76; p<0.05 in all cases). There was no correlation between stroke index or fatigue index and blood acid-base status. Analysis of the swimming speed in the 8 x 25 m test seems to be helpful in evaluation of lactate tolerance (anaerobic capacity) in collegiate swimmers.     

Estimation of the anaerobic threshold from heart rate variability in an incremental swimming test

ABSTRACT: Di Michele, R, Gatta, G, Di Leo, A, Cortesi, M, Andina, F, Tam, E, Da Boit, M, and Merni, F. Estimation of the anaerobic threshold from heart rate variability in an incremental swimming test. J Strength Cond Res 26(11): 3059-3066, 2012-This study aimed to evaluate, in swimming, the agreement between the anaerobic threshold (AT) as determined from the analysis of blood lactate concentration ([La]) and from a new method based on the heart rate (HR) variability (HRV). Fourteen high-level swimmers completed an incremental 7 × 200-m front crawl test, during which the HRV was measured continuously and [La] was collected after each step. To individuate the AT, the trends of the high-frequency HRV spectral power (HFPOW) and of the fraction of HFPOW relative to the respiratory sinus arrhythmia (HFPOW-RSA) were analyzed. In all the subjects, an abrupt increase of both HFPOW and HFPOW-RSA was observed and associated with the AT. The AT parameters determined, respectively, from [La] and HFPOW-RSA were similar (p > 0.05) and highly correlated (HR: 182.0 ± 8.1 vs. 181.1 ± 8.2 b·min, r = 0.93, 95% limits of agreement [LoA]: -6.7 to 4.9 b·min; velocity: 1.47 ± 0.11 vs. 1.47 ± 0.11 m·s, r = 0.98, 95% LoA: -0.05 to 0.05 m·s). Instead, the AT HR and velocity obtained from HFPOW (179.2 ± 8.4 b·min; 1.45 ± 0.11 m·s) were correlated to the corresponding parameters determined from [La] (HR: r = 0.84; velocity: r = 0.94) but underestimated them slightly (95% LoA: -11.9 to 6.3 b·min and -0.11 to 0.05 m·s). These results demonstrate that the AT can be assessed from the HRV in swimming, providing an important testing tool for coaches. Furthermore, using the actual respiratory spectral component, rather than the total HF spectral power, allows us to obtain a more accurate estimate of AT parameters.