Time limit at VO2max velocity in elite crawl swimmers.

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.

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.

Evaluation of the energy expenditure in competitive swimming strokes.

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.

Relationships between energetic, stroke determinants, and velocity in butterfly.

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.

Energy cost and intracyclic variation of the velocity of the centre of mass in butterfly stroke.

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.

Time limit and VO2 slow component at intensities corresponding to VO2max in swimmers.

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.

Precocious puberty.

Puberty occurring before the age of 8 years in girls and 9 years in boys in considered precocious. The numerous causes of precocity can be classified as central or peripheral. Central or true precocious puberty (CPP) is due to premature activation of the hypothalamopituitary-gonadal axis and is isosexual. Peripheral or pseudoprecocious puberty (PPP) results from the production of sex steroids independent of the H-P-G axis and may be isosexual or heterosexual. CPP is the most common form of precocity involving more than 50% of children and is much more common in girls than boys. CPP is more common between 4 and 8 years. A peak serum LH levels > 10 iu/l following GnRH stimulation is the absolute evidence of CPP. Serum IGF-I levels are predictive of the outcome. Availability of CT and MRI has helped to determine the cause of CPP in most cases. Hypothalamic hamartoma is the most common tumour causing CPP especially in boys. Adrenal causes, particularly CAH, are the commonest cause of PPP in boys whereas ovarian causes are more likely in girls. Long acting GnRH analogues provide a safe and effective form of treatment of CPP.

Profile of growth hormone deficiency in Bombay.

Of the 430 children referred for the evaluation of short stature 100 (23%) were confirmed to have growth hormone deficiency. The male to female ratio was 1.94:1. Less than 10% belonged to the lower socio-economic group. Most of the cases (73%) presented between the ages of 6-15 years though growth failure was usually recognised earlier. Minimum of two stimulation tests were performed in each case. Seventy five GH deficient children had idiopathic GHD (IGHD) and 31% of these were familial. Fourteen had organic causes and 11 had GH resistance. Of 75 with IGHD, 18 had abnormal deliveries, breech or birth asphyxia. Multitropic pituitary hormone deficiency (MPHD) was found in 9/75 cases of idiopathic GHD and in three of the organic group. The height age was much more retarded than chronologic age in the GH resistant group (p less than 0.05) and the HA/BA ratio was also lowest in this group (p less than 0.001). Growth velocity was less than 4 cm/year in all the GHD children but was lowest in those with MPHD. The interesting feature of this study is the marked predominance of the familial cases 31% and a high incidence of growth hormone resistant cases (11%).

Short stature in Indian children: the extent of the problem.

PIP: A study of child growth included 2500 consecutive admissions to Bai Jerbai Wadia Hospital for Children in Bombay, India. 140 (5.6%) were considered to be of short stature (less than the 5th percentile of an Indian standard). The causes of growth retardation were in order of frequency: protein energy malnutrition (42), chronic systemic disease (23), chronic anemia (19), skeletal disorders (16), constitutional short stature (15), endocrine disorders (15), intrauterine growth retardation (5), chromosomal disorders (2), and miscellaneous (3). All 10.7% of cases with endocrine problems had congenital hypothyroidism. A study of short stature among 430 children referred to the same hospital's endocrine clinic showed endocrine disorders were responsible for most short stature cases (143 or 33.3%). 97 of these cases (67.8%) had a deficiency of growth hormone, while just 6.3% suffered from hypothyroidism. Malnutrition and chronic disease caused short stature in just 8.4%. Another survey conducted in the outpatient clinic showed that the height of 50 of 500 (10%) children was below the 5th percentile of the Indian standard. 32% were below the 3rd percentile of a Western standard. A study of 200 children referred to the hospital for their short stature demonstrated that 132 (66%) were below the 5th percentile of the Indian standard. 67.8% of the children between the Indian standard's 5th percentile and the Western standard's 3rd percentile were of normal variant short stature. In fact, 90.4% of their heights compared to their parents' heights. 56.8% of those below the 5th percentile had endocrine problems and just 19.6% correlated with their parents' height. 52% of these children were deficient in growth hormone. Therefore, growth hormone deficiency accounted for 20% of all short stature cases.^ieng

Identification of a child with short stature.

The objective of this study was to determine the utility of Indian Council of Medical Research's (ICMR) height percentile standards in comparison to Tanner's, in the evaluation of children with short stature. The study consisted of an initial survey of the heights of 500 consecutive new cases brought to the Out Patient Department. The heights were assessed by both ICMR and Tanner's standards. Only 10% were below the 5th percentile of ICMR standards while as many as 32% were below the 3rd percentile of Tanner's standards. Two hundred children who were referred to the endocrine clinic primarily for short stature and who were below the 3rd percentile of Tanner's standards were then evaluated. Of these 200 short children 132 (66%) were also below the 5th percentile of ICMR standards. The major causes of short stature in those below the 5th percentile of ICMR standards were endocrine (56.8%). In the group between the 5th percentile of ICMR standards and 3rd percentile of Tanner standards the major cause of growth retardation was normal variant short stature (67.8% of cases in this group). Correlation of the child's height with the mid-parental height was seen in 90.4% in this group but in only 16.6% of those below the 5th percentile of ICMR standards. The ICMR standards may, therefore, be more suitable than Tanner's standards for the identification of a short child from the lower socio-economic groups.