Accelerometer-based prediction of skeletal mechanical loading during walking in normal weight to severely obese subjects.

There is no objective way to monitor mechanical loading characteristics during exercise for bone health improvement. We developed accelerometry-based equations to predict ground reaction force (GRF) and loading rate (LR) in normal weight to severely obese subjects. Equations developed had a high and moderate accuracy for GRF and LR prediction, respectively, thereby representing an accessible way to determine mechanical loading characteristics in clinical settings. INTRODUCTION: There is no way to objectively prescribe and monitor exercise for bone health improvement in obese patients based on mechanical loading characteristics. We aimed to develop accelerometry-based equations to predict peak ground reaction forces (pGRFs) and peak loading rate (pLR) on normal weight to severely obese subjects. METHODS: Sixty-four subjects (45 females; 84.6 ± 21.7 kg) walked at different speeds (2-6 km·h-1) on a force plate-equipped treadmill while wearing accelerometers at lower back and hip. Regression equations were developed to predict pGRF and pLR from accelerometry data. Leave-one-out cross-validation was used to calculate prediction accuracy and Bland-Altman plots. Actual and predicted values at different speeds were compared by repeated measures ANOVA. RESULTS: Body mass and peak acceleration were included for pGRF prediction and body mass and peak acceleration transient rate for pLR prediction. All pGRF equation coefficients of determination were above 0.89, a good agreement between actual and predicted pGRFs, with a mean absolute percent error (MAPE) below 6.7%. No significant differences were observed between actual and predicted pGRFs at each walking speed. Accuracy indices from our equations were better than previously developed equations for normal weight subjects, namely a MAPE approximately 3 times smaller. All pLR prediction equations presented a lower accuracy compared to those developed to predict pGRF. CONCLUSION: Walking pGRF and pLR in normal weight to severely obese subjects can be predicted with moderate to high accuracy by accelerometry-based equations, representing an easy and accessible way to determine mechanical loading characteristics in clinical settings.

AquaTrainer® Snorkel does not Increase Hydrodynamic Drag but Influences Turning Time.

Our purpose was to verify if the use of the new AquaTrainer(®) respiratory snorkel lead to an increase of front crawl hydrodynamic drag and whether the constraint of using an adapted turning technique influences its corresponding turning time. 12 swimmers performed 2 (without and with snorkel) 12×25 front crawl repetitions from low to maximal velocity on the measuring active drag system. Complementarily, 3 swimming turns were compared: open turn with snorkel, tumble turn and open turn without snorkel. Drag values were similar without vs. with snorkel at 0.9, 1.1, 1.3, 1.5 and 1.7 m.s(-1) velocities: 15.84 ±5.32 vs. 16.18±4.81, 25.60±6.69 vs. 26.03±6.17, 38.37±8.04 vs. 38.88±7.56, 54.64±10.06 vs. 55.08±9.55, 74.77±14.09 vs. 74.92±13.14 N, (respectively, p≥0.05), and high agreement between conditions was observed (p<0.01). Front crawl swimming with snorkel using the open turn implied an increase in turning time of 14.2 and 5.1% than the tumble turn and open turn without the apparatus (p<0.01). AquaTrainer(®) snorkel does not lead to an increase in active drag during front crawl performed at a large range of velocities and, consequently, the metabolic energy necessary to overcome total drag will not be affected. However, turning with it requires an additional time that should be taken into account in scientific research and training conditions.

VO2 kinetics and metabolic contributions during full and upper body extreme swimming intensity.

PURPOSE: Our purpose was to characterize the oxygen uptake ([Formula: see text]) kinetics, assess the energy systems contributions and determine the energy cost when swimming front crawl at extreme intensity. Complementarily, we compared swimming full body with upper body only. METHODS: Seventeen swimmers performed a 100 m maximal front crawl in two conditions: once swimming with full body and other using only the upper propulsive segments. The [Formula: see text] was continuously measured using a telemetric portable gas analyser (connected to a respiratory snorkel), and the capillary blood samples for lactate concentration analysis were collected. RESULTS: A sudden increase in [Formula: see text] in the beginning of exercise, which continuously rose until the end of the bout (time: 63.82 ± 3.38 s; [Formula: see text]: 56.07 ± 5.19 ml min(-1) kg(-1); [Formula: see text] amplitude: 41.88 ± 4.74 ml min(-1) kg(-1); time constant: 12.73 ± 3.09 s), was observed. Aerobic, anaerobic lactic and alactic pathways were estimated and accounted for 43.4, 33.1 and 23.5 % of energy contribution and 1.16 ± 0.10 kJ m(-1) was the energy cost. Complementarily, the absence of lower limbs lead to a longer time to cover 100 m (71.96 ± 5.13 s), slower [Formula: see text] kinetics, lower aerobic and anaerobic (lactic and alactic) energy production and lower energy cost. CONCLUSION: Despite the short duration of the event, the aerobic energy contribution covers about 50 % of total metabolic energy liberation, highlighting that both aerobic and anaerobic energy processes should be developed to improve the 100 m swimming performance. Lower limbs action provided an important contribution in the energy availability in working muscles being advised its full use in this short duration and very high-intensity event.

Which are the best VO2 sampling intervals to characterize low to severe swimming intensities?

Cardiorespiratory response in swimming has been used to better understand aerobic performance, especially by assessing oxygen uptake (VO2). The current study aimed to compare different VO2 time-averaging intervals throughout low to severe swimming intensities, hypothesizing that VO2 values are similar for different time averages at low to moderate and heavy swimming intensities, but not for the severe domain. 20 male trained swimmers completed an incremental protocol of 7×200 m until exhaustion (0.05 m/s increments and 30 s intervals). VO2 was measured by a portable gas analyser connected to a snorkel system. 6 time average intervals (breath-by-breath, 5, 10, 15, 20 and 30 s) were compared for all the protocol steps. Breath-by-breath and 5 s average exhibited higher VO2 values than averages≥10 s for all swimming intensities (P≤0.02; partial η(2)≤0.28). VO2 values did not differ between 10, 15, 20 and 30 s averages throughout the incremental protocol (P>0.05; partial η(2)≤0.05). Furthermore, 10 and 15 s averages showed the lowest VO2 mean difference (0.19 mL( · )kg(-1 · )min(-1)). For the 6 time average intervals analysed, 10 and 15 s averages were those that showed the lowest changes on VO2 values. We recommended the use of 10 and 15 s time averaging intervals to determine relevant respiratory gas exchange parameters along a large spectrum of swimming intensities.

Kinematic and electromyographic changes during 200 m front crawl at race pace.

The purpose of this study was to analyse eventual kinematic and electromyographic changes during a maximal 200 m front crawl at race pace. 10 male international level swimmers performed a 200 m maximal front crawl test. Images were recorded by 2 above and 4 under water cameras, and electromyographic signals (EMG) of 7 upper and lower limbs muscles were analysed for 1 stroke cycle in each 50 m lap. Capillary blood lactate concentrations were collected before and after the test. The variables of interest were: swimming speed, stroke length, stroke and kick frequency, hand angular velocity, upper limb and foot displacement, elbow angle, shoulder and roll angle, duration of stroke phases, and EMG for each muscle in each stroke phase. Generally, the kinematic parameters decreased, and a relative duration increased for the entry and pull phases and decreased for the recovery phase. Muscle activation of flexor carpi radialis, biceps brachii, triceps brachii, peitoral major and upper trapezius increased during specific stroke phases over the test. Blood lactate concentration increased significantly after the test. These findings suggest the occurrence of fatigue, characterised by changes in kinematic parameters and selective changes in upper limbs muscle activation according to muscle action.

Is the new AquaTrainer® snorkel valid for VO2 assessment in swimming?

The Cosmed AquaTrainer® snorkel, in connection with the K4b2 analyzer, is the most recent instrument used for real time gas analysis during swimming. This study aimed to test if a new AquaTrainer® snorkel with 2 (SV2) or 4 (SV4) valves is comparable to a standard face mask (Mask) being valid for real time gas analysis under controlled laboratory and swimming pool conditions. 9 swimmers performed 2 swimming and 3 cycling tests at 3 different workloads on separate days. Tests were performed in random order, at constant exercise load with direct turbine temperature measurements, breathing with Mask, SV4 and SV2 while cycling, and with SV2 and SV4 while swimming. A high agreement was obtained using Passing - Bablok regression analysis in oxygen consumption, carbon dioxide production, tidal volumes, pulmonary ventilation, expiratory fraction of oxygen and carbon dioxide, and heart rate comparing different conditions in swimming and cycling. Proportional and fixed differences were always rejected (95% CI always contained the value 1 for the slope and the 0 for the intercept). In conclusion, the new SV2 AquaTrainer® snorkel, can be considered a valid device for gas analysis, being comparable to the Mask and the SV4 in cycling, and to the SV4 in swimming.

Biomechanical framework for the inverse dynamic analysis of swimming using hydrodynamic forces from swumsuit.

This study aims to integrate an open-source software capable of estimating hydrodynamic forces solely from kinematic data with a full-body biomechanical model of the human body to enable inverse dynamic analyses of swimmers. To demonstrate the methodology, intersegmental forces and joint torques of the lower limbs were computed for a six-beat front crawl swimming motion, acquired at LABIOMEP-UP. The hydrodynamic forces obtained compare well with existing numerical literature. The intersegmental forces and joint torques obtained increase from distal to proximal joints. Overall, the results are consistent with the limited literature on swimming biomechanics, which provides confidence in the presented methodology.

Intracycle velocity variation of the body centre of mass in front crawl.

Our aim was to determine the 3-dimensional intracycle velocity variation (IVV) of the body centre of mass during a 200-m front crawl event, and to analyse its relation with the segmental hand kinematics and the velocity (v) changes. 10 high-level male swimmers performed a 200-m front crawl swim at maximal intensity. 2 above- and 4 underwater cameras were used to record one complete non-breathing cycle for each 50-m lap, and APASystem was used for imaging processing. The coefficient of variation was calculated to assess the IVV in the horizontal (x), vertical (y), and lateral (z) axes; hand kinematics was also computed. IVV remained stable across the 200 m, and significant correlations were found between vx and vmaxx (r=0.55), vminx (r = 0.68), IVVx (r = -0.45), and IVVz (r = -0.45) (all p≤0.01). In addition, IVVx was correlated with the backward horizontal amplitude normalized to stroke length (r = 0.54), IVVy with hand angular velocity (r = -0.40), and IVVz with the elbow angle range in the pull phase (r = - 0.37) (all p<0.05). This study shows the stability of the IVV (x,y,z), the inverse relation of the IVV (x, z) with v, the direct relation of the vmaxx and vminx with v, and the influence of the hand kinematics in the IVV.

Gross efficiency and energy expenditure in kayak ergometer exercise.

We purposed to study energy expenditure, power output and gross efficiency during kayak ergometer exercise in 12 elite sprint kayakers. 6 males (age 24.2±4.8 years, height 180.4±4.8 cm, body mass 79.7±8.5 kg) and 6 females (age 24.3±4.5 years, height 164.5±3.9 cm, body mass 65.4±3.5 kg), performed an incremental intermittent protocol on kayak ergometer with VO2 and blood lactate concentration assessment, a non-linear increase between power output and energy expenditure being observed. Paddling power output, energy expenditure and gross efficiency corresponding to VO2max averaged 199.92±50.41 W, 75.27±6.30 ml.kg - 1.min - 1, and 10.10±1.08%. Male kayakers presented higher VO2max, power output and gross efficiency at the VO2max, and lower heart rate and maximal lactate concentration than females, but no differences were found between genders regarding energy expenditure at VO2max. Aerobic and anaerobic components of energy expenditure evidenced a significant contribution of anaerobic energy sources in sprint kayak performance. Results also suggested the dependence of the gross efficiency on the changes in the amount of the aerobic and anaerobic contributions, at heavy and severe intensities. The inter-individual variance of the relationship between energy expenditure and the corresponding paddling power output revealed a relevant tracking for females (FDγ=0.73±0.06), conversely to the male group (FDγ=0.27±0.08), supporting that some male kayakers are more skilled in some paddling intensities than others.

Different VO2max time-averaging intervals in swimming.

We aimed to determine the effect of sampling interval strategy on VO(2max) assessment to establish a standard time averaging method that allows a better identification of the VO(2) plateau incidence in swimming. To this end, 3 incremental protocols utilizing different step lengths for each sampling interval were used to compare VO(2max)measurements. 11 trained male swimmers performed 3 repetitions of a front crawl intermittent incremental protocol until exhaustion (increments of 0.05 m.s(-1), with 30 s and 24-48 h intervals between steps and tests, respectively) with 200, 300 and 400-m step lengths. VO(2) was directly measured, and 6 sampling intervals were compared: bxb and averages of 5, 10, 15, 20 and 30 s. Shorter sampling intervals (≤ 15 s) allowed the highest incidence of the VO(2) plateau, independent of the step lengths used; the 200 and 300-m step protocols accounted for higher percentage of VO(2) plateau incidence, and higher VO(2max) values, compared to the 400-m step protocol. As an optimal sampling interval should be used for the validation of the research findings, and considering that swimmers and coaches prefer less time-consuming protocols, the use of the 10 s time-average interval (once bxb and 5 s samplings present high variability) in a 200-m step incremental protocol for VO(2max) assessment in swimming is suggested.

Anaerobic critical velocity in four swimming techniques.

The aim of this study was to assess critical velocity in order to control and evaluate anaerobic swimming training. 51 highly trained male swimmers performed maximal 15, 25, 37.5 and 50 m in the 4 swimming techniques to determine critical velocity from the distance-time relationship. Anaerobic critical velocity was compared with 100 m swimming performance and corresponding partials. Complementarily, 9 swimmers performed a 6×50 m (4 min interval) training series at front crawl individual anaerobic critical velocity, capillary blood lactate concentrations being assessed after each repetition. The mean±SD values of anaerobic critical velocity and its relationship with the 100 m event were: 1.61±0.07 (r=0.60, p=0.037), 1.53±0.05 (r=0.81, p=0.015), 1.33±0.05 (r=0.83, p=0.002), and 1.75±0.05 (r=0.74, p=0.001), for butterfly, backstroke, breaststroke and front crawl, respectively. However, differences between anaerobic critical velocity and performance were observed (with exception of the second half of the 100 m swimming events in breaststroke and butterfly). Lactate concentration values at the end of the series were 14.52±1.06 mmol.l (-1), which suggests that it was indeed an anaerobic training set. In this sense, anaerobic critical velocity can be used to prescribe anaerobic training intensities.

Step length and individual anaerobic threshold assessment in swimming.

Anaerobic threshold is widely used for diagnosis of swimming aerobic endurance but the precise incremental protocols step duration for its assessment is controversial. A physiological and biomechanical comparison between intermittent incremental protocols with different step lengths and a maximal lactate steady state (MLSS) test was conducted. 17 swimmers performed 7×200, 300 and 400 m (30 s and 24 h rest between steps and protocols) in front crawl until exhaustion and an MLSS test. The blood lactate concentration values ([La-]) at individual anaerobic threshold were 2.1±0.1, 2.2±0.2 and 1.8±0.1 mmol.l - 1 in the 200, 300 and 400 m protocols (with significant differences between 300 and 400 m tests), and 2.9±1.2 mmol.l - 1 at MLSS (higher than the incremental protocols); all these values are much lower than the traditional 4 mmol.l - 1 value. The velocities at individual anaerobic threshold obtained in incremental protocols were similar (and highly related) to the MLSS, being considerably lower than the velocity at 4 mmol.l - 1. Stroke rate increased and stroke length decreased throughout the different incremental protocols. It was concluded that it is valid to use intermittent incremental protocols of 200 and 300 m lengths to assess the swimming velocity corresponding to individual anaerobic threshold, the progressive protocols tend to underestimate the [La-] at anaerobic threshold assessed by the MLSS test, and swimmers increase velocity through stroke rate increases.

Biomechanical analysis of backstroke swimming starts.

The relationships between the start time and kinematic, kinetic and electromyographic data were examined in order to establish the common features of an effective backstroke swimming start. Complementarily, different starting positions were analysed to identify the parameters that account for the fastest backstroke start time under different constraints. 6 high-level swimmers performed 4×15 m maximal trials of each start variants with different feet position: parallel and entirely submerged (BSFI) and above water surface (BSFE), being monitored with synchronized dual-media image, underwater platform plus handgrip with a load cell, and eletromyographic signal of RECTUS FEMORIS and GASTROCNEMIUS MEDIALIS. Mean and SD values of start time for BSFI and BSFE were 2.03 ± 0.19 and 2.14 ± 0.36 s, respectively. In both starts, high associations (r > =0.75, p < 0.001) were observed between start time and centre of mass resultant average velocity at glide phase and horizontal impulse at take-off for BSFI, and centre of mass horizontal position at the start signal for BSFE. It was concluded that the greater impulse during the take-off and its transformation into a fast underwater movement are determinant to decrease the start time at BSFI. Regarding BSFE, a greater centre of mass pool-wall approximation might imply a flatter take-off angle, compromising underwater velocity and starting performance.

VO2 kinetics in 200-m race-pace front crawl swimming.

Studies that aim to characterize oxygen uptake kinetics in efforts above maximal oxygen consumption intensity are scarce. Our aim was to analyze the oxygen kinetics in a maximal 200-m front crawl, all measurements being conducted in swimming pool conditions. 10 high-level male swimmers performed a maximal 200-m bout and oxygen uptake was directly measured through breath-by-breath gas analysis. Mean (±SD) peak oxygen uptake was 68.58 (±5.79) ml.kg(-1).min(-1), evidencing a fast component phase. As expected, peak oxygen uptake presented a direct relationship with mean swimming speed of the first 50-m lap and with the 200-m effort, and was also correlated with the amplitude of the fast component (r=0.75, r=0.72, r=0.73, p<0.05, respectively). The observed mean amplitude value was higher than those observed in the literature for other exercise intensity domains. However, the time for its onset, as well as the duration for attaining the steady state, was shorter, as the peak oxygen uptake was not correlated with these 2 components. Moreover, as previously described for swimming at high intensities, the slow component phenomenon was not observed. Aerobic metabolic pathway accounted for 78.6%, confirming the high aerobic contribution in middle distance swimming events.

Does the hip reflect the centre of mass swimming kinematics?

The purpose of this study was to determine the relationship between the hip point and the centre of mass for kinematical parameters (displacement, velocity and acceleration) in the three axes of motion. One complete stroke cycle was analyzed in eight swimmers performing a 25 m front crawl swim test at high intensity. Within-subject correlation coefficients were computed between the centre of mass and both hips, as well as mean of the errors, RMS error and a paired sample t-test. High correlation coefficients were found for the displacement in the horizontal direction (r=1.00 for both hips) and low to moderate correlation coefficients (r=-0.01 to r=0.54) were found for all other studied variables. Moreover, moderate to large RMS errors were observed: (i) between 0.05 and 0.15 for the displacement; (ii) between 0.16 and 0.30 for the velocity and (iii) between 5.28 and 7.86 for the acceleration. Complementarily, RMS errors for the intracyclic velocity variation were between 0.07 and 0.18. Considering the centre of mass and hip values statistical differences were found in velocity in x, acceleration in x and y, and intracyclic velocity variation in y axes. Therefore, results suggest that the hip point does not represent most kinematical parameters of the estimated centre of mass in front crawl swimming.

Differences in spatial-temporal parameters and arm-leg coordination in butterfly stroke as a function of race pace, skill and gender.

Spatial-temporal parameters (velocity, stroke rate, stroke length) and arm-leg coordination in the butterfly stroke were studied as a function of race pace, skill (due to technical level, age, and experience) and gender. Forty swimmers (ten elite men, ten elite women, ten less-skilled men, and ten less-skilled women) performed the butterfly stroke at four velocities corresponding to the appropriate paces for the 400-m, 200-m, 100-m, and 50-m, respectively. Arm and leg stroke phases were identified by video analysis and used to calculate four time gaps (T1: the time difference between the start of the arms' catch phase and the start of the legs' downward phase of the first leg kick; T2: the time difference between the start of the arms' pull phase and the start of the legs' upward phase of the first leg kick; T3: the time difference between the start of the arms' push phase and the start of the legs' downward phase of the second leg kick; and T4: the time difference between the start of the arms' recovery and the start of the legs' upward phase of the second leg kick) and the total time gap (TTG), i.e., the sum of the four discrete time gaps. These values described the changing coupling of arm to leg actions over an entire stroke cycle. A significant race pace effect indicated that the synchronization between the key motor points of the arms and legs, which determine the starts and ends of the arm and leg stroke phases, increased with pace for all participants. A significant skill effect indicated that the elite swimmers had greater velocity, stroke length, and stroke rate and stronger synchronization of the arm and leg stroke phases than the less-skilled swimmers, due to smaller T2 and T3 and greater T1. A significant gender effect revealed greater velocity and stroke length for the men, and smaller T1 for the less-skilled women. These time gap differences between skill levels were related to the capacity of elite swimmers to assume a more streamlined position of trunk, head and upper limbs during leg actions, adopt a shorter glide and higher stroke rate to overcome great forward resistance, and generate higher forces and use better technique during the arm pull. Thus, coaches are advised to begin monitoring arm-leg coordination earlier in swimmers' careers to ensure that they attain their highest possible skill levels.

Intensity- and muscle-specific fascicle behavior during human drop jumps.

The present study was designed to examine fascicle-tendon interaction in the synergistic medial gastrocnemius (MG) and soleus (Sol) muscles during drop jumps (DJ) performed from different drop heights (DH). Eight subjects performed unilateral DJ with maximal rebounds on a sledge apparatus from different DH. During the exercises, fascicle lengths (using ultrasonography) and electromyographic activities were recorded. The results showed that the fascicles of the MG and Sol muscles behaved differently during the contact phase, but the whole muscle-tendon unit and its tendinous tissue lengthened before shortening in both muscles. The Sol fascicles also lengthened before shortening during the ground contact in all conditions. During the braking phase, the Sol activation increased with increasing DH. However, the amplitude of Sol fascicle lengthening was not dependent on DH during the same phase. In the MG muscle, the fascicles primarily shortened during the braking phase in the lower DH condition. However, in the higher DH conditions, the MG fascicles either behaved isometrically or were lengthened during the braking phase. These results suggest that the fascicles of synergistic muscles (MG and Sol) can behave differently during DJ and that, with increasing DH, there may be specific length change patterns of the fascicles of MG but not of Sol.

Does net energy cost of swimming affect time to exhaustion at the individual's maximal oxygen consumption velocity?

AIM: The purpose of the present study was to examine the relationship between time limit at the minimum velocity that elicits the individual's maximal oxygen consumption (TLim-v VO2max) and three swimming economy related parameters: the net energy cost corresponding to v VO2max (Cv VO2max), the slope of the regression line obtained from the energy expenditure (E) and corresponding velocities during an incremental test (C(slope)) and the ratio between the mean E value and the velocity mean value of the incremental test (C(inc)). Complementarily, we analysed the influence of Cv VO2max, C(slope) and C(inc) on TLim-v VO2max by swimming level. METHODS: Thirty swimmers divided into 10 low-level (LLS) (4 male and 6 female) and 20 highly trained swimmers (HTS) (10 of each gender) performed an incremental test for v VO2max assessment and an all-out TLim-v VO2max test. RESULTS: TLim-v VO2max, v VO2max, Cv fVO2max, C(slope) and C(inc) averaged, respectively, 313.8+/-63 s, 1.16+/-0.1 m x s(-1), 13.2+/-1.9 J x kg(-1) x m(-1), 28+/-3.2 J x kg(-1) x m(-1) and 10.9+/-1.8 J x kg(-1) x m(-1) in the LLS and 237.3+/-54.6 s, 1.4+/-0.1 m x s(-1), 15.6+/-2.2 J x kg(-1) x m(-1), 36.8+/-4.5 J x kg(-1) x m(-1) and 13+/-2.3 J x kg(-1) x m(-1) in the HTS. TLim-v VO2max was inversely related to C(slope) (r = -0.77, P < 0.001), and to v VO2max (r = -0.35, P = 0.05), although no relationships with the Cv VO2max and the C(inc) were observed. CONCLUSIONS: The findings of this study confirmed exercise economy as an important factor for swimming performance. The data demonstrated that the swimmers with higher and v VO2max performed shorter time in TLim-v VO2max efforts.

Behavioural variability and motor performance: Effect of practice specialization in front crawl swimming.

The aim was to examine behavioural variability within and between individuals, especially in a swimming task, to explore how swimmers with various specialty (competitive short distance swimming vs. triathlon) adapt to repetitive events of sub-maximal intensity, controlled in speed but of various distances. Five swimmers and five triathletes randomly performed three variants (with steps of 200, 300 and 400m distances) of a front crawl incremental step test until exhaustion. Multi-camera system was used to collect and analyse eight kinematical and swimming efficiency parameters. Analysis of variance showed significant differences between swimmers and triathletes, with significant individual effect. Cluster analysis put these parameters together to investigate whether each individual used the same pattern(s) and one or several patterns to achieve the task goal. Results exhibited ten patterns for the whole population, with only two behavioural patterns shared between swimmers and triathletes. Swimmers tended to use higher hand velocity and index of coordination than triathletes. Mono-stability occurred in swimmers whatever the task constraint showing high stability, while triathletes revealed bi-stability because they switched to another pattern at mid-distance of the task. Finally, our analysis helped to explain and understand effect of specialty and more broadly individual adaptation to task constraint.

Metabolic and ventilatory thresholds assessment in front crawl swimming.

AIM: The purpose of this study was to assess and characterize the ventilatory anaerobic threshold in swimming, and to verify if the anaerobic metabolic threshold could be accurately estimated using ventilatory parameters. METHODS: Twenty-eight national-level male swimmers performed a n x 200 m front crawl individualized intermittent incremental protocol, with 30 s rest intervals, until exhaustion. The ventilatory variables and heart rate were continuously measured using a telemetric portable gas analyser. The capillary blood samples for lactate concentration analysis were collected from the earlobe at rest, during rest intervals, and at the end of exercise. RESULTS: No significant differences were observed between the ventilatory and metabolic thresholds for lactate concentration, heart rate and velocity (P=0.62, 0.80 and 0.78, respectively). The Bland-Altman plot revealed higher agreement between both methods for heart rate and velocity values. Ventilatory anaerobic threshold occurred at a swimming velocity corresponding to 88% of maximal oxygen uptake and lactate concentration mean values at ventilatory and metabolic thresholds were lower than 3 mmol.L(-1). CONCLUSION: Swimming anaerobic metabolic threshold could be accurately estimated using ventilatory parameters. Moreover, ventilatory anaerobic threshold occurred at similar %VO2max than in other sports. The lactate concentration mean values at ventilatory and metabolic thresholds were lower than the reference value of 4 mmol.L(-1) evidencing that, in highly trained swimmers, individualized values of anaerobic threshold should be used instead of general references.