No abstract

This study aimed to characterise both the VO2 kinetics within constant heavy-intensity swimming exercise, and to assess the relationships between VO2 kinetics and other parameters of aerobic fitness, in well-trained swimmers. On separate days, 21 male swimmers completed: (1) an incremental swimming test to determine their maximal oxygen uptake (VO2 max), first ventilatory threshold (VT), and the velocity associated with VO2max (vVO(2 max)) and (2) two square-wave transitions from rest to heavy-intensity exercise, to determine their VO2 kinetics. All the tests involved breath-by-breath analysis of freestyle swimming using a swimming snorkel. VO2 kinetics was modelled with two exponential functions. The mean values for the incremental test were 56.0 ± 6.0 ml min(-1) kg(-1), 1.45 ± 0.08 m s(-1); and 42.1 ± 5.7 ml min(-1) kg(-1) for VO2 max, vVO(2 max) and VT, respectively. For the square-wave transition, the time constant of the primary phase (sp) averaged 17.3 ± 5.4 s and the relevant slow component (A'sc) averaged 4.8 ± 2.9 ml min(-1) kg(-1) [representing 8.9% of the end-exercise VO2 (%A'sc)]. sp was correlated with vVO(2 max) (r = -0.55, P = 0.01), but not with either VO2max (r = 0.05, ns) or VT (r = 0.14, ns). The %A' sc did not correlate with either VO2max (r = -0.14, ns) or vVO(2 max) (r = 0.06, ns), but was inversely related with VT (r = -0.61, P < 0.01). This study was the first to describe the VO2 kinetics in heavy-intensity swimming using specific swimming exercise and appropriate methods. As has been demonstrated in cycling, faster VO2 kinetics allow higher aerobic power outputs to be attained. The slow component seems to be reduced in swimmers with higher ventilatory thresholds.

This study compared the validity of reported equations as predictors of peak VO(2) in 8-10-year-old children. Participants (90 boys and girls aged 8-10 years) performed the multistage-shuttle-run-test (MSRT) and peak VO(2) was measured in field using a portable gas analyser. The equations that estimated peak VO(2) from the MSRT performance were chosen according to the age range of this study. As follows, the FITNESSGRAM reports and the equations of Leger et al. (Can J Appl Sport Sci 5: 77-84, 1988), Barnett et al. (Pediatr Exerc Sci 5:42-50, 1993), Matsuzaka et al. (Pediatr Exerc Sci 16:113-125, 2004) and Fernhall et al. (Am J Ment Retard 102:602-612, 1998) were used to estimate the peak VO(2) and compared with the directly measured value. The equation of Leger et al. (Can J Appl Sport Sci 5: 77-84, 1988) provided a mean difference (d) of 4.7 ml kg(-1) min(-1) and a 1.0 slope. The equation of Matsuzaka et al. (Pediatr Exerc Sci 16:113-125, 2004)(a) using maximal speed (MS) showed a higher d (5.4) than the remaining using total laps d (4.2). The equation of Barnett et al. (Pediatr Exerc Sci 5:42-50, 1993)(a) that includes triceps skinfold and MS showed the highest d (6.1) but the smallest range (24.1) and slope (0.6). Data from the FITNESSGRAM had the smallest d (1.8 ml kg(-1) min(-1)), but also had the highest range between limits of agreement (28.6 ml kg(-1) min(-1)) and a 1.2 slope. The lowest slope (0.4) and range (22.2 ml kg(-1) min(-1)) were observed using the equation of Fernhall et al. (Am J Ment Retard 102:602-612, 1998). Log transformation of the data revealed that the equations of Matsuzaka et al. (Pediatr Exerc Sci 16:113-125, 2004)(a) (1.1*/÷1.25) and Fernhall et al. (Am J Ment Retard 102:602-612, 1998) (1.17*/÷1.25) showed the closest agreement among all, but they still yield unsatisfactory accuracy.

Information regarding the effects of stretching intensity on the joint torque-angle response is scarce. The present study examined the effects of three static stretching protocols with different intensities and durations on the passive knee extension torque-angle response of seventeen male participants (age ± SD: 23.9 ± 3.6 years, height: 177.0 ± 7.2 cm, BMI: 22.47 ± 1.95 kg · m(2)). The stretching intensity was determined according to the maximal tolerable torque of the first repetition: fifty per cent (P50), seventy-five per cent (P75) and the maximum intensity without pain (P100). Five repetitions were performed for each protocol. The stretch duration of each repetition was 90, 135 and 180 s for P100, P75 and P50, respectively. The rest period between repetitions was 30 s. Passive torque at a given angle, angle, stress relaxation, area under the curve, surface electromyography activity and visual analogue scale score were compared. The significant (P < 0.05) results found were as follows: (i) the P50 and P75 did not increase the angle and passive peak torque outcomes, despite more time under stretch; (ii) only the P100 increased the angle and passive peak torque outcomes; (iii) the perception of stretching intensity mainly changed depending on knee angle changes, and not passive torque; (iv) the P50 induced a higher passive torque decrease; (v) when protocols were compared for the same time under stretch, the torque decrease was similar; (vi) the change in torque-angle curve shape was different depending on the stretching protocol. In conclusion, higher stretch duration seems to be a crucial factor for passive torque decrease and higher stretch intensity for maximum angle increase.

The purpose of this study was to understand the ventilatory and physiological responses immediately below and above the maximal lactate steady-state (MLSS) velocity and to determine the relationship of oxygen uptake (VO2) kinetics parameters with performance, in swimmers. Competitive athletes (N = 12) completed in random order and on different days a 400-m all-out test, an incremental step test comprising 5 × 250- and 1 × 200-m stages and 30 minutes at a constant swimming velocity (SV) at 87.5, 90, and 92.5% of the maximal aerobic velocity for MLSS velocity (MLSSv) determination. Two square-wave transitions of 500 m, 2.5% above and below the MLSSv were completed to determine VO2 on-kinetics. End-exercise VO2 at 97.5 and 102.5% of MLSSv represented, respectively, 81 and 97% of VO2max; the latter was not significantly different from maximal VO2 (VO2max). The VO2 at MLSSv (49.3 ± 9.2 ml·kg(-1)·min(-1)) was not significantly different from the second ventilatory threshold (VT2) (51.3 ± 7.6 ml·kg(-1)·min(-1)). The velocity associated with MLSS seems to be accurately estimated by the SV at VT2 (vVT2), and vVO2max also seems to be estimated with accuracy from the central 300-m mean velocity of a 400-m trial, indicators that represent a helpful tool for coaches. The 400-m swimming performance (T400) was correlated with the time constant of the primary phase VO2 kinetics (τp) at 97.5% MLSSv, and T800 was correlated with τp in both 97.5 and 102.5% of MLSSv. The assessment of the VO2 kinetics in swimming can help coaches to build training sets according to a swimmer's individual physiological response.