João Paulo Vilas-Boas

Head Posture and Neck Pain of Chronic Nontraumatic Origin: A Comparison Between Patients and Pain-Free Persons

OBJECTIVE To compare standing head posture measurements between patients with nontraumatic neck pain (NP) and pain-free individuals. DESIGN Single-blind (assessor) cross-sectional study. SETTING Hospital and general community. PARTICIPANTS Consecutive patients (n=40) with chronic nontraumatic NP and age- and sex-matched pain-free participants (n=40). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Three angular measurements: the angle between C7, the tragus of the ear, and the horizontal; the angle between the tragus of the ear, the eye, and the horizontal; and the angle between the inferior margins of the right and the left ear and the horizontal were calculated through the digitization of video images. RESULTS NP patients were found to have a significantly smaller angle between C7, the tragus, and the horizontal, resulting in a more forward head posture than pain-free participants (NP, mean +/- SD, 45.4 degrees +/-6.8 degrees ; pain-free, mean +/- SD, 48.6 degrees +/-7.1 degrees ; P<.05; confidence interval [CI] for the difference between groups, 0.9 degrees -6.3 degrees ). Dividing the population according to age into younger (</=50y) and older (>50y) revealed an interaction, with a statistically significant difference in head posture for younger participants with NP compared with younger pain-free participants (NP, mean +/- SD, 46.1 degrees +/-6.7 degrees ; pain-free, mean +/- SD, 51.8 degrees +/-5.9 degrees ; P<.01; CI for the difference between groups, 1.8 degrees -9.7 degrees ) but no difference for the older group (NP, mean +/- SD, 44.8 degrees +/-7.1 degrees ; pain-free, mean +/- SD, 45.1 degrees +/-6.7 degrees ; P>.05; CI for the difference between groups, -4.9 degrees -4.2 degrees ). No other differences were found between patients and pain-free participants. CONCLUSIONS Younger patients with chronic nontraumatic NP were shown to have a more forward head posture in standing than matched pain-free participants. However, the difference, although statistically significant, was perhaps too small to be clinically meaningful.

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.

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.

Different profiles of the aerial start phase in front crawl

Seifert, L, Vantorre, J, Lemaitre, F, Chollet, D, Toussaint, HM, and Vilas-Boas, JP. Different profiles of the aerial start phase in front crawl. J Strength Cond Res 24(2): 507-516, 2010-This study analyzed the kinematics and kinetics (jumping ability) of the aerial start phase in 11 elite front crawl sprinters. The aim was to determine whether a particular start technique leads to a short 15 m start time or whether several start profiles contribute equally well. All swimmers performed 3 starts using their preferential style, which was the grab start for all, followed by a 25-m swim at maximal velocity. Countermovement jump enabled to determine vertical jumping ability. Using a video device, phase durations, angles at takeoff and entry, and hip velocity were assessed. Correlation between all variables and the 15 m start time established the common features of an effective start but also revealed great intersubject variability. Cluster analysis enabled to distinguish 4 start profiles (flat, pike, flight, and Volkov), indicating that several individual profiles lead to short 15 m start times. It could be advised to consider the intersubject variability in relation to start time before favoring unique strategy.

Ground reaction forces and plantar pressure distribution during occasional loaded gait

This study compared the ground reaction forces (GRF) and plantar pressures between unloaded and occasional loaded gait. The GRF and plantar pressures of 60 participants were recorded during unloaded gait and occasional loaded gait (wearing a backpack that raised their body mass index to 30); this load criterion was adopted because is considered potentially harmful in permanent loaded gait (obese people). The results indicate an overall increase (absolute values) of GRF and plantar pressures during occasional loaded gait (p < 0.05); also, higher normalized (by total weight) values in the medial midfoot and toes, and lower values in the lateral rearfoot region were observed. During loaded gait the magnitude of the vertical GRF (impact and thrust maximum) decreased and the shear forces increased more than did the proportion of the load (normalized values). These data suggest a different pattern of GRF and plantar pressure distribution during occasional loaded compared to unloaded gait.

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.

Time to Exhaustion at the VO2max Velocity in Swimming: A Review

Time to Exhaustion at the VO2max Velocity in Swimming: A Review The aim of this study was to present a review on the time to exhaustion at the minimum swimming velocity corresponding to maximal oxygen consumption (TLim-vVO2max). This parameter is critical both for the aerobic power and the lactate tolerance bioenergetical training intensity zones, being fundamental to characterize it, and to point out its main determinants. The few number of studies conducted in this topic observed that swimmers were able to maintain an exercise intensity corresponding to maximal aerobic power during 215 to 260 s (elite swimmers), 230 to 260 s (high level swimmers) and 310 to 325 s (low level swimmers), and no differences between genders were reported. TLim-vVO2max main bioenergetic and functional determinants were swimming economy and VO2 slow component (direct relationship), and vVO2max, velocity at anaerobic threshold and blood lactate production (inverse relationship); when more homogeneous groups of swimmers were analysed, the inverse correlation value between TLim-vVO2max and vVO2max was not so evident. In general, TLim-vVO2max was not related to VO2max. TLim-vVO2max seems also to be influenced by stroking parameters, with a direct relationship to stroke length and stroke index, and an inverse correlation with stroke rate. Assessing TLim-vVO2max, together with the anaerobic threshold and the biomechanical general parameters, will allow a larger spectrum of testing protocols application, helping to build more objective and efficient training programs.

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.

Swimming simulation: a new tool for swimming research and practical applications

This chapter covers topics in swimming simulation from a computational fluid dynamics perspective. This perspective means emphasis on the fluid mechanics and CFD methodology applied in swimming research. We concentrated on numerical simulation results, considering the scientific simulation point-of-view and especially the practical implications with swimmers.

Autonomic adaptation after traditional and reverse swimming training periodizations

The objective of the present study was to analyze the autonomic response of trained swimmers to traditional and reverse training periodization models. Seventeen swimmers were divided in two groups, performing a traditional periodization (TPG) or a reverse periodization (RPG) during a period of 10 weeks. Heart rate variability and 50 m swimming performance were analyzed before and after the training programs. After training, the TPG decreased the values of the high frequency band (HF), the number of differences between adjacent normal R-R intervals longer than 50 ms (NN50) and the percentage of differences between adjacent normal R-R intervals more than 50 ms (pNN50), and the RPG increased the values of HF and square root of the mean of the sum of the squared differences between adjacent normal R-R intervals (RMSSD). None of the groups improved significantly their performance in the 50-m test. The autonomic response of swimmers was different depending on the periodization performed, with the reverse periodization model leading to higher autonomic adaption. Complementary, the data suggests that autonomic adaptations were not critical for the 50-m swimming performance.