The purpose of this study was to examine the relationship between the intra-cycle variation of the horizontal velocity of displacement (dV) and the energy cost (EC) in butterfly stroke. Five Portuguese national level swimmers performed one maximal and two sub-maximal 200-m butterfly swims. The oxygen consumption was measured breath-by-breath by portable metabolic cart. A respiratory snorkel and valve system with low hydrodynamic resistance was used to measure pulmonary ventilation and to collect breathing air samples. Blood samples from the ear lobe were collected before and after each swim to analyse blood lactate concentration. Total energy expenditure ( E (tot)) and EC were calculated for each swim. The swims were videotaped in the sagittal plane with a set of two cameras providing dual projection from both underwater and above the water surface. The APAS system was used to analyse dV for the centre of mass. The E (tot) increased linearly with the increasing V, presenting a significant correlation coefficient between these parameters ( r =0.827, P <0.001). The increase in EC was significantly associated with the increase in the dV ( r =0.807, P <0.001). All data were presented as the mean value and the standard deviation. It is concluded that high intra-cycle variation of the velocity of the centre of mass was related to less efficient swimming and vice versa for the butterfly stroke.

The purpose of this study was to measure and compare the total energy expenditure of the four competitive swimming strokes. Twenty-six swimmers of international level were submitted to an incremental set of 200-m swims (5 swimmers at Breaststroke, 5 swimmers at Backstroke, 4 swimmers at Butterfly and 12 swimmers at Front Crawl). The starting velocity was approximately 0.3 m x s (-1) less than a swimmer's best performance and thereafter increased by 0.05 m x s (-1) after each swim until exhaustion. Cardio-pulmonary and gas exchange parameters were measured breath-by-breath (BxB) for each swim to analyze oxygen consumption (VO2) and other energetic parameters by portable metabolic cart (K4b(2), Cosmed, Rome, Italy). A respiratory snorkel and valve system with low hydrodynamic resistance was used to measure pulmonary ventilation and to collect breathing air samples. Blood samples from the ear lobe were collected before and after each swim to analyze blood lactate concentration (YSI 1500 L, Yellow Springs, Ohio, USA). Total energy expenditure (E(tot)), was calculated for each 200-m stage. E (tot) differed significantly between the strokes at all selected velocities. At the velocity of 1.0 m x s (-1) and of 1.2 m x s (-1) the E(tot) was significantly higher in Breaststroke than in Backstroke, in Breaststroke than in Freestyle and in Butterfly than in Freestyle. At the velocity of 1.4 m x s (-1), the E(tot) was significantly higher in Breaststroke than in Backstroke, in Backstroke than in Freestyle, in Breaststroke than in Freestyle and in Butterfly than in Freestyle. At the velocity of 1.6 m x s (-1), the E(tot) was significantly higher in Breaststroke and in Butterfly than in Freestyle. As a conclusion, E(tot) of well-trained competitive swimmers was measured over a large range of velocities utilising a new BxB technique. Freestyle was shown to be the most economic among the competitive swimming strokes, followed by the Backstroke, the Butterfly and the Breaststroke.

The purpose of this study is to assess, with elite crawl swimmers, the time limit at the minimum velocity corresponding to maximal oxygen consumption (TLim-vVO2max), and to characterize its main determinants. Eight subjects performed an incremental test for vVO2max assessment and, forty-eight hours later, an all-out swim at vVO2max until exhaustion. VO2 was directly measured using a telemetric portable gas analyzer and a visual pacer was used to help the swimmers keeping the predetermined velocities. Blood lactate concentrations, heart rate and stroke parameter values were also measured. TLim-vVO2max and vVO2max, averaged, respectively, 243.2 +/- 30.5 s and 1.45 +/- 0.08 m . s (-1). TLim-vVO2max correlated positively with VO2 slow component (r = 0.76, p < 0.05). Negative correlations were found between TLim-vVO2max and body surface area (r = - 0.80) and delta lactate (r = - 0.69) (p < 0.05), and with vVO2max (r = - 0.63), v corresponding to anaerobic threshold (r = - 0.78) and the energy cost corresponding to vVO2max (r = - 0.62) (p < 0.10). No correlations were observed between TLim-vVO2max and stroking parameters. This study confirmed the tendency to TLim-vVO2max be lower in the swimmers who presented higher vVO2max and vAnT, possibly explained by their higher surface area, energy cost and anaerobic rate. Additionally, O2SC seems to be a determinant of TLim-vVO2max.

The purpose of this study was to identify the relationship between the bioenergetical and the biomechanical variables (stroke parameters), through a range of swimming velocities, in butterfly stroke. Three male and one female butterflier of international level were submitted to an incremental set of 200-m butterfly swims. The starting velocity was 1.18 m . s (-1) for the males and 1.03 m . s (-1) for the female swimmer. Thereafter, the velocity was increased by 0.05 m . s (-1) after each swim until exhaustion. Cardio-pulmonary and gas exchange parameters were measured breath by breath for each swim to analyze oxygen consumption and other energetic parameters by portable metabolic cart (K4b (2), Cosmed, Rome, Italy). A respiratory snorkel and valve system with low hydrodynamic resistance was used to measure pulmonary ventilation and to collect breathing air samples. Blood samples from the ear lobe were collected before and after each swim to analyze blood lactate concentration (YSI 1500 L, Yellow Springs, US). Total energy expenditure (E (tot)), energetic cost (EC), stroke frequency (SF), stroke length (SL), mean swimming velocity (V), and stroke index (SI) were calculated for each lap and average for each 200-m stage. Correlation coefficients between E (tot) and V, EC, and SF, as well as between EC and SI were statistically significant. For the relation between EC and SL, only one regression equation presented a correlation coefficient with statistical significance. Relations between SF and V, as well as between SI and V were significant in all of the swimmers. Only two individual regression equations presented statistically significant correlation coefficient values for the relation established between V and the SL. As a conclusion, the present sample of swims demonstrated large inter individual variations concerning the relationships between bioenergetic and biomechanical variables in butterfly stroke. Practitioners should be encouraged to analyze the relationships between V, SF, and SL individually to detect the deflection point in SL in function of swimming velocity to further determine appropriate training intensities when trying to improve EC.

The purpose of this study was to measure, in swimming pool conditions and with high level swimmers, the time to exhaustion at the minimum velocity that elicits maximal oxygen consumption (TLim at vVO(2)max), and the corresponding VO(2) slow component (O(2)SC). The vVO(2)max was determined through an intermittent incremental test (n = 15). Forty-eight hours later, TLim was assessed using an all-out swim at vVO(2)max until exhaustion. VO(2) was measured through direct oximetry and the swimming velocity was controlled using a visual light-pacer. Blood lactate concentrations and heart rate values were also measured. Mean VO(2)max for the incremental test was 5.09 +/- 0.53 l/min and the corresponding vVO(2)max was 1.46 +/- 0.06 m/s. Mean TLim value was 260.20 +/- 60.73 s and it was inversely correlated with the velocity of anaerobic threshold (r = -0.54, p < 0.05). This fact, associated with the inverse relationship between TLim and vVO(2)max (r = -0.47, but only for p < 0.10), suggested that swimmers' lower level aerobic metabolic rate might be associated with a larger capacity to sustain that exercise intensity. O(2)SC reached 274.11 +/- 152.83 l/min and was correlated with TLim (r = 0.54), increased ventilation in TLim test (r = 0.52) and energy cost of the respiratory muscles (r = 0.51), for p < 0.05. These data suggest that O(2)SC was also observed in the swimming pool, in high level swimmers performing at vVO(2)max, and that higher TLim seems to correspond to higher expected O(2)SC amplitude. These findings seem to bring new data with application in middle distance swimming.