Caroline Ruschel

Loading forces in shallow water running in two levels of immersion.

OBJECTIVE To analyse the vertical and anteroposterior components of the ground reaction force during shallow water running at 2 levels of immersion. SUBJECTS Twenty-two healthy adults with no gait disorders, who were familiar with aquatic exercises. METHODS Subjects performed 6 trials of water running at a self-selected speed in chest and hip immersion. Force data were collected through an underwater force plate and running speed was measured with a photocell timing light system. Analysis of covariance was used for data analysis. RESULTS Vertical forces corresponded to 0.80 and 0.98 times the subjects body weight at the chest and hip level, respectively. Anteroposterior forces corresponded to 0.26 and 0.31 times the subjects body weight at the chest and hip level, respectively. As the water level decreased the subjects ran faster. No significant differences were found for the force values between the immersions, probably due to variability in speed, which was self-selected. CONCLUSION When thinking about load values in water running professionals should consider not only the immersion level, but also the speed, as it can affect the force components, mainly the anteroposterior one. Quantitative data on this subject could help professionals to conduct safer aqua-tic rehabilitation and physical conditioning protocols.

Ground reaction forces in shallow water running are affected by immersion level, running speed and gender

OBJECTIVES To analyze the effect of depth of immersion, running speed and gender on ground reaction forces during water running. DESIGN Controlled laboratory study. METHODS Twenty adults (ten male and ten female) participated by running at two levels of immersion (hip and chest) and two speed conditions (slow and fast). Data were collected using an underwater force platform. The following variables were analyzed: vertical force peak (Fy), loading rate (LR) and anterior force peak (Fx anterior). Three-factor mixed ANOVA was used to analyze data. RESULTS Significant effects of immersion level, speed and gender on Fy were observed, without interaction between factors. Fy was greater when females ran fast at the hip level. There was a significant increase in LR with a reduction in the level of immersion regardless of the speed and gender. No effect of speed or gender on LR was observed. Regarding Fx anterior, significant interaction between speed and immersion level was found: in the slow condition, participants presented greater values at chest immersion, whereas, during the fast running condition, greater values were observed at hip level. The effect of gender was only significant during fast water running, with Fx anterior being greater in the men group. Increasing speed raised Fx anterior significantly irrespective of the level of immersion and gender. CONCLUSIONS The magnitude of ground reaction forces during shallow water running are affected by immersion level, running speed and gender and, for this reason, these factors should be taken into account during exercise prescription.

Incidência de lesões em velejadores brasileiros de diferentes níveis técnicos

The first step to reduce the incidence of injuries in athletes is to assess the characteristics of occurrence, providing background for the structure and application of prevention programs. This study had the aim to investigate the incidence of injuries in sailing athletes of different technical levels. The sample was composed of 172 sailors, divided in three groups: 89 beginners, participants in the Optimist qualifying of the World Championship (group 1); 29 juvenile sailors, participants in the Youth Sailing Cup (group 2) and 54 national elite sailors, participants in the Pre-Olympic Sailing Week (group 3). The data collection instrument was a mixed questionnaire and the data were analyzed by descriptive statistics. Five athletes from group 1 (5.6%); five athletes from group 2 (17.2%) and 15 athletes from group 3 (27.8%) reported some kind of injury related with the modality. Higher incidence of injury was observed in the back and knee and the most reported diagnostic was muscular injury, followed by cuts, sprains and tendinitis. The incidence in sailing is low if compared with other sport modalities, despite the high physical demand required during the actions on the boat. It was verified that the professional athletes, who had higher age mean and time of practice, suffered the most injuries. On the other hand, the lowest incidence was among children and adolescents. Therefore, it is important that prevention programs start from the first years of practice in order to reduce the risk to future outbreaks, especially of chronic nature. Based on this information concerning kinds of injury, we suggest inclusion of exercises specific to musculature conditioning and compensation in the training programs, as well as stretching and relaxation sessions.

Kinematic, kinetic and EMG analysis of four front crawl flip turn techniques

Abstract This study aimed to analyse the kinematic, kinetic and electromyographic characteristics of four front crawl flip turn technique variants. The variants distinguished from each other by differences in body position (i.e. dorsal, lateral, ventral) during rolling, wall support, pushing and gliding phases. Seventeen highly trained swimmers (17.9 ± 3.2 years old) participated in interventional sessions and performed three trials of each variant, being monitored with a 3-D video system, a force platform and an electromyography (EMG) system. Studied variables: rolling time and distance, wall support time, push-off time, peak force and horizontal impulse at wall support and push-off, centre of mass horizontal velocity at the end of the push-off, gliding time, centre of mass depth, distance, average and final velocity during gliding, total turn time and electrical activity of Gastrocnemius Medialis, Tibialis Anterior, Biceps Femoris and Vastus Lateralis muscles. Depending on the variant, total turn time ranged from 2.37 ± 0.32 to 2.43 ± 0.33 s, push-off force from 1.86 ± 0.33 to 1.92 ± 0.26 BW and centre of mass velocity during gliding from 1.78 ± 0.21 to 1.94 ± 0.22 m · s−1. The variants were not distinguishable in terms of kinematical, kinetic and EMG parameters during the rolling, wall support, pushing and gliding phases.

Ground Reaction Force and Cadence during Stationary Running Sprint in Water and on Land.

This study was aimed at analyzing the cadence (Cadmax) and the peak vertical ground reaction force (Fymax) during stationary running sprint on dry land and at hip and chest level of water immersion. We hypothesized that both Fymax and Cadmax depend on the level of immersion and that differences in Cadmax between immersions do not affect Fymax during stationary sprint. 32 subjects performed the exercise at maximum cadence at each immersion level and data were collected with force plates. The results show that Cadmax and Fymax decrease 17 and 58% from dry land to chest immersion respectively, with no effect of cadence on Fymax. While previous studies have shown similar neuromuscular responses between aquatic and on land stationary sprint, our results emphasize the differences in Fymax between environments and levels of immersion. Additionally, the characteristics of this exercise permit maximum movement speed in water to be close to the maximum speed on dry land. The valuable combination of reduced risk of orthopedic trauma with similar neuromuscular responses is provided by the stationary sprint exercise in water. The results of this study support the rationale behind the prescription of stationary sprinting in sports training sessions as well as rehabilitation programs.

Análise da frequência e do comprimento de braçada em provas de 50, 100 e 200m costas na natação

Introduction: This study aimed to analyze and compare the stroke efficiency indicators: average velocity (Av), stroke rate (SR) and stroke length (SL) on 50m, 100m and 200m backstroke events. Materials and Methods: Fourteen swimmers (seven men and seven women) were intentionally selected, mean age 20±4 years old among the 16 finalists of the 50m, 100m and 200m backstroke in XXXVI Brazilian Absolute Swimming Championship José Finkel Trophy 2007, held in the Greater Florianópolis, SC, Brazil. The variables were described by average, standard deviation and coefficient of variation, as all different distances were compared trough ANOVA oneway (Tukey Post-Hoc) and correlated through Pearson correlation test (p<0.05). Results: The results are in accordance to the literature: the smaller distances have a higher SR and a lesser SL with a higher Av. The values are reversed for larger distances, where it has a lesser SR and a higher SL, but Av decreases. Discussion: For coaches and swimmers, it is suggested to develop the technical aspects for a better combination of SR and SL, aiming at an ideal balance to maintain higher speed independently on the distance.

Isokinetic hip muscle strength: a systematic review of normative data

Abstract The aim of this study was to conduct a systematic review to determine the quality of evidence of studies assessing isokinetic hip muscle strength in adult non-injured individuals. We also aimed to summarise and pool data of normative values for hip muscle strength. The influence of methodological and participant-related factors on hip strength performance was explored as well. Guidelines proposed in the PRISMA were used to undertake a search strategy involving the keyword ‘hip’ associated with a set of keywords reflecting muscle strength. Five databases were searched: ProQuest, PubMed, Science Direct, Scopus and Web of Science. From the 2,939 records initially retained, 28 articles were included in this systematic review. Eight articles were classified as high quality. This systematic review exposed the methodological fragility of most studies assessing hip strength in non-injured adult population. Only data from studies with a small number of participants are available to be used as reference. A few individual studies suggest no differences in torque parameters between dominant and non-dominant lower limbs; differences in torque parameters between age groups; and between male and female participants. Overall, reference values for hip muscle performance in isokinetic tests are mostly unclear.

Vertical ground reaction force in stationary running in water and on land: A study with a wide range of cadences

PURPOSE The aim of this study was to analyze the effect of cadence, immersion level as well as body density on the vertical component (Fymax) of ground reaction force (GRF) during stationary running (SR). METHODS In a controlled, laboratory study, thirty-two subjects ran at a wide range of cadences (85-210 steps/min) in water, immersed to the hip and to the chest, and on dry land. Fymax. was verified by a waterproof force measurement system and predicted based on a statistical model including cadence, immersion ratio and body density. RESULTS The effect of cadence was shown to depend on the environment: while Fymax increases linearly with increasing cadence on land; in water, Fymax reaches a plateau at both hip and chest immersions. All factors analyzed, cadence, immersion level and body density affected Fymax significantly, with immersion (aquatic × land environment) showing the greatest effect. In water, different cadences may lead to bigger changes in Fymax than the changes obtained by moving subjects from hip to chest immersion. A regression model able to predict 69% of Fymax variability in water was proposed and validated. CONCLUSION Cadence, Immersion and body density affect Fymax in a significant and non-independent way. Besides a model of potential use in the prescription of stationary running in water, our analysis provides insights into the different responses of GRF to changes in exercise parameters between land and aquatic environment.

Hand force symmetry during breaststroke swimming

Hand force symmetry during breaststroke swimming The aim of this study was to analyze the hand force symmetry during the breaststroke and its relationship with swimmers’ performance. Seventeen breaststroke and/or medley specialists participated (12 men and 5 women, 19.5 ± 5.2 years and average performance of 73.4 ± 7% of the 50 m breaststroke world record). Each swimmer performed three repetitions of 25 m breaststroke swimming at maximal speed. Pressure sensors from Aquanex acquisition system were placed in both swimmers’ hands and Mean Force (Fmean) and Maximal Force (Fmax) were measured. The symmetry index proposed by Sanders was calculated and the time of a 50-m breaststroke trial at maximum speed (T50m) was used as a performance indicator. The variables were compared between hands using tests for dependent samples, and the relationship between variables were investigated using Spearman correlation test. The Fmean applied was 47.9 ± 16.7 N and 47.9 ± 14.5 N for right and left hands, respectively. The Fmean corresponded to 120.7 ± 43.6 N e 112.8 ± 35.7 N for right and left hand, respectively. No signifi cant differences were observed for none of the variables between right and left hands. Analyzing the subjects individually, it was possible to observe asymmetries levels up to 30.6% for Fmean and 35.9% for Fmax, however the relationship between symmetry indexes and the 50 m breaststroke performance was not statistically signifi cant.

Skin Cooling and Force Replication at the Ankle in Healthy Individuals: A Crossover Randomized Controlled Trial

CONTEXT Proprioception of the ankle is determined by the ability to perceive the sense of position of the ankle structures, as well as the speed and direction of movement. Few researchers have investigated proprioception by force-replication ability and particularly after skin cooling. OBJECTIVE To analyze the ability of the ankle-dorsiflexor muscles to replicate isometric force after a period of skin cooling. DESIGN Randomized controlled clinical trial. SETTING Laboratory. PATIENTS OR OTHER PARTICIPANTS Twenty healthy individuals (10 men, 10 women; age = 26.8 ± 5.2 years, height = 171 ± 7 cm, mass = 66.8 ± 10.5 kg). INTERVENTION(S) Skin cooling was carried out using 2 ice applications: (1) after maximal voluntary isometric contraction (MVIC) performance and before data collection for the first target force, maintained for 20 minutes; and (2) before data collection for the second target force, maintained for 10 minutes. We measured skin temperature before and after ice applications to ensure skin cooling. MAIN OUTCOME MEASURE(S) A load cell was placed under an inclined board for data collection, and 10 attempts of force replication were carried out for 2 values of MVIC (20%, 50%) in each condition (ice, no ice). We assessed force sense with absolute and root mean square errors (the difference between the force developed by the dorsiflexors and the target force measured with the raw data and after root mean square analysis, respectively) and variable error (the variance around the mean absolute error score). A repeated-measures multivariate analysis of variance was used for statistical analysis. RESULTS The absolute error was greater for the ice than for the no-ice condition (F1,19 = 9.05, P = .007) and for the target force at 50% of MVIC than at 20% of MVIC (F1,19 = 26.01, P < .001). CONCLUSIONS The error was greater in the ice condition and at 50% of MVIC. Skin cooling reduced the proprioceptive ability of the ankle-dorsiflexor muscles to replicate isometric force.