P. Colaço

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 Etot 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.

Assessment of individual anaerobic threshold and stroking parameters in swimmers aged 10–11 years

Abstract The assessment of blood lactate concentration is considered essential for the physiological diagnosis of swimming performance. But for a more detailed and complete analysis of a swimmers strengths and weaknesses, it is also important to examine his or her technical characteristics. However, few studies have combined physiological and technical evaluation in child swimmers. The aim of the present study was to assess the metabolic anaerobic threshold (blood lactate concentration and corresponding swimming velocity) of 10- to 11-year-old swimmers (n=15) using an individualized intermittent incremental protocol. Comparison was made with the traditionally used 4 mmol · l−1 lactate threshold. In addition, stroke rate, stroke length, and stroke index were measured throughout the experimental protocol for assessment of the anaerobic threshold. Each swimmer performed a front crawl 5×200 m test, in which the swimming velocity was controlled by an acoustic signal each 50 m. Blood samples were collected from the ear lobe (Lactate Pro, Arkay, Inc., Kyoto, Japan), at rest and after each step. Stroke rate was registered by a Seiko base 3 chronofrequencemeter; stroke length, stroke index, and velocity were calculated at the end of each 200 m. The individual anaerobic threshold occurred at 2.3 mmol · l−1 (s=0.59), and the corresponding velocity was 1.026 m · s−1 (s=0.053), much lower than the traditionally used 4 mmol · l−1 value (or even 3.5 mmol · l−1). The velocity corresponding to 4 mmol · l−1 and 3.5 mmol · l−1 was 1.081 m · s−1 (s=0.056) and 1.067 m · s−1 (s=0.055), respectively. Stroke rate increased and stroke length decreased throughout the incremental protocol (i.e. with increasing velocity). The stroke index showed a tendency to increase throughout the protocol, with a significant difference from the first to the second step. The velocity corresponding to 4 mmol · l−1 (and 3.5 mmol · l−1) does not represent the metabolic individual anaerobic threshold in trained swimmers, independently of their age, and age-group swimmers prefer to increase their velocity through an increase in stroke rate. Thus, given the importance of developing swimming technique in age-group swimmers, coaches should implement the lengthening of swimmers stroke cycles in their training practice routines, so that they limit the effects of reduced stroke length when velocity increases.

Anaerobic Threshold Individualized Assessment in a Young Swimmer

The assessment of blood lactate concentrations is considered one essential procedure in physiological diagnosis of swimming performance. Our purpose was to assess the metabolic anaerobic threshold of an 11 year old swimmer through an individualized intermittent incremental protocol. Complementarily, stroking parameters were also determined. The subject performed a front crawl 5 x 200 m test, being the velocity controlled by an acoustic signal. The blood samples were collected from the ear lobe at rest and after each step. Stroke rate was registered by a chronofrequencemeter base 3, and stroke length and velocity were calculated at the end of each 200 m. The individual anaerobic threshold occurred at 1.2 mmol/l, rather lower than the traditionally used 4 mmol/l value suggested for trained swimmers. The velocity corresponding to anaerobic threshold was 1.06 m/s, representing a 5 s difference in a 100 m effort comparing to the velocity of 4 mmol/l. Stroke rate increased and stroke length decreased throughout the incremental protocol, i.e., with the velocity increments. It was concluded that the velocity corresponding to 4 mmol/l does not represent the individual anaerobic threshold in this young trained swimmer, and that he prefer to increase their velocity through the raise of stroke rate. Thus, given the importance of developing swimming technique in age-group swimmers, this swimmer should implement the lengthening of his stroke cycles in the training practice routines, trying to resist to the degradation of the stroke length when velocity increases.

Perceptions of the Neighborhood Environment Associated With Walking at Recommended Intensity and Volume Levels in Recreational Senior Walkers

ABSTRACT This study examined the relationship of perceived neighborhood environment factors with recommended volume and intensity of walking in recreational senior walkers. A sample of 85 seniors used an accelerometer and completed the ALPHA questionnaire. Binomial logistic regressions were conducted to detect associations. Perceptions about traffic safety (odds ratio [OR] = 4.395; 95% confidence interval [CI] = 1.024; 18.866) and pleasant environment (OR = 8.718; 95% CI = 1.803; 42.149) were positively related with the achievement of 10,000 steps per day, in older women. The perception of nearby parks was positively associated with the compliance with peak 30-minutes cadence above 100, in older men (OR = 14.353; CI 95% = 1.321; 15.591). No more significant associations were found between perceptions of the neighborhood environment and walking at recommended intensity and volume levels. These results indicated that community initiatives that encourage traffic safety, pleasant environment, and parks may be a promising direction to promote walking at recommended volume and intensity in senior walkers.

The Experience of Older Adults in a Walking Program at Individual, Interpersonal, and Environmental Levels

ABSTRACT Walking programs are advocated to mobilize sedentary older adults. Thus, the study of age-specific social ecological walking programs are needed in order to develop interventions that offer best chance for success. The purpose of this study was to analyze the experience of participating in a walking program at individual, interpersonal, and environmental levels in order to identify appropriate strategies for walking interventions to older adults. A 10-month walking program was implemented, three times a week with 19 older adults (mean age = 67,42 ± 2,48). The participants were submitted to a pre and post evaluation of functional fitness, physical activity patterns, and perceptions of their neighborhood environment. After the program, semi-structured interviews were conducted with 12 randomly selected participants. The results highlight the potential of this walking program by enhancing physical and mental health, creating supportive social networks, and a context of walking in nature which was crucial for the promotion of the active lifestyle and functional improvement of older adults participants.

Anaerobic Threshold Individualized Assessment in a Young Swimmer~!2009-07-05~!2009-11-10~!2010-08-13~!

The assessment of blood lactate concentrations is considered one essential procedure in physiological diagnosis of swimming performance. Our purpose was to assess the metabolic anaerobic threshold of an 11 year old swimmer through an individualized intermittent incremental protocol. Complementarily, stroking parameters were also determined. The subject performed a front crawl 5 x 200 m test, being the velocity controlled by an acoustic signal. The blood samples were collected from the ear lobe at rest and after each step. Stroke rate was registered by a chronofrequencemeter base 3, and stroke length and velocity were calculated at the end of each 200 m. The individual anaerobic threshold occurred at 1.2 mmol/l, rather lower than the traditionally used 4 mmol/l value suggested for trained swimmers. The velocity corresponding to anaerobic threshold was 1.06 m/s, representing a 5 s difference in a 100 m effort comparing to the velocity of 4 mmol/l. Stroke rate increased and stroke length decreased throughout the incremental protocol, i.e., with the velocity increments. It was concluded that the velocity corresponding to 4 mmol/l does not represent the individual anaerobic threshold in this young trained swimmer, and that he prefer to increase their velocity through the raise of stroke rate. Thus, given the importance of developing swimming technique in age-group swimmers, this swimmer should implement the lengthening of his stroke cycles in the training practice routines, trying to resist to the degradation of the stroke length when velocity increases.