Use of a backpack alters gait initiation of high school students.

We assessed how backpack carriage influences the gait initiation (GI) process in high school students, who extensively use backpacks. GI involves different dynamics from gait itself, while the excessive use of backpacks can result in adverse effects. 117 high school students were evaluated in three experimental conditions: no backpack (NB), bilateral backpack (BB), and unilateral backpack (UB). Two force plates were used to acquire ground reaction forces (GRFs) and moments for each foot separately. Center of pressure (COP) scalar variables were extracted, and statistical parametric mapping analysis was performed over the entire COP/GRFs time series. GI anticipatory postural adjustments (APAs) were reduced and were faster in backpack conditions; medial-lateral COP excursion was smaller in this phase. The uneven distribution of the extra load in the UB condition led to a larger medial-lateral COP shift in the support-foot unloading phase, with a corresponding vertical GRF change that suggests a more pronounced unloading swing foot/loading support foot mechanism. The anterior-posterior GRFs were altered, but the COP was not. A possible explanation for these results may be the forward trunk lean and the center of mass proximity of the base of support boundary, which induced smaller and faster APA, increased swing foot/support foot weight transfer, and increased load transfer to the first step.

Back Pain Prevalence and Its Associated Factors in Brazilian Athletes from Public High Schools: A Cross-Sectional Study.

Most studies on the prevalence of back pain have evaluated it in developed countries (Human Development Index--HDI > 0.808), and their conclusions may not hold for developing countries. The aim of this study was to identify the prevalence of back pain in representative Brazilian athletes from public high schools. This cross-sectional study was performed during the state phase of the 2015 Jogos dos Institutos Federais (JIF), or Federal Institutes Games, in Brazil (HDI = 0.744), and it enrolled 251 athletes, 173 males and 78 females (14-20 years old). The dependent variable was back pain, and the independent variables were demographic, socioeconomic, psychosocial, hereditary, exercise-level, anthropometric, strength, behavioral, and postural factors. The prevalence ratio (PR) was calculated using multivariable analysis according to the Poisson regression model (α = 0.05). The prevalence of back pain in the three months prior to the study was 43.7% (n = 104), and 26% of the athletes reported feeling back pain only once. Multivariable analysis showed that back pain was associated with demographic (sex), psychosocial (loneliness and loss of sleep in the previous year), hereditary (ethnicity, parental back pain), strength (lumbar and hand forces), anthropometric (body mass index), behavioral (sleeping time per night, reading and studying in bed, smoking habits in the previous month), and postural (sitting posture while writing, while on a bench, and while using a computer) variables. Participants who recorded higher levels of lumbar and manual forces reported a lower prevalence of back pain (PR < 0.79), whereas feeling lonely in the previous year, obesity, and ethnicity exhibited the highest prevalence ratio (PR > 1.30). In conclusion, there is no association between exercise levels and back pain but there is an association between back pain and non-exercise related variables.

Effects of four days hiking on postural control.

Hiking is a demanding form of exercise that may cause delayed responses of the postural muscles and a loss of somatosensory information, particularly when repeatedly performed for several days. These effects may negatively influence the postural control of hikers. Therefore, the aim of this study was to investigate the effects of a four-day hike on postural control. Twenty-six adults of both sexes travelled 262 kilometers, stopping for lunch and resting in the early evening each day. Force platforms were used to collect center of pressure (COP) data at 100 Hz for 70 seconds before hiking started and immediately after arriving at the rest station each day. The COP time course data were analyzed according to global stabilometric descriptors, spectral analysis and structural descriptors using sway density curve (SDC) and stabilometric diffusion analysis (SDA). Significant increases were found for global variables in both the anterior-posterior and medial-lateral directions (COP sway area, COP total sway path, COP mean velocity, COP root mean square value and COP range). In the spectral analysis, only the 80% power frequency (F80) in the anterior-posterior direction showed a significant increase, reflecting the increase of the sway frequencies. The SDC revealed a significant increase in the mean distance between peaks (MD) and a significant decrease in the mean peak amplitudes (MP), suggesting that a larger torque amplitude is required for stabilization and that the postural stability is reduced. The SDA revealed a decrease in the long-term slope (Hl) and increases in the short-term (Ks) and the long-term (Kl) intercepts. We considered the likelihood that the presence of local and general fatigue, pain and related neuromuscular adaptations and somatosensory deficits may have contributed to these postural responses. Together, these results demonstrated that four days of hiking increased sway frequencies and deteriorated postural control in the standing position.

[Evaluation of gait initiation in low risk pregnant women in the three trimesters]. / Avaliação da inicialização da marcha na gestante de baixo risco nos três trimestres gestacionais.

PURPOSES: To describe the process of gait initiation of pregnant women and to compare the behavior of the pressure center in the three trimesters of pregnancy. METHODS: Fifty-seven low-risk pregnant women were evaluated, aged 18 to 35 years, selected for convenience location during the three trimesters of pregnancy. The women were divided into three groups of 19 subjects each, according to gestational age - 1st quarter (4-12 weeks), 2nd quarter (13-28 weeks), and 3rd quarter (29-42 weeks,). Each patient was positioned standing up with one foot on each AMTI force platform until she heard a beep indicating that she should start walking a distance of four meter. Data were analyzed using the SPSS software. The Kolmogorov Smirnov test, Tukey's test and Spearman correlation coefficient were used for group comparisons, with 5% significance level in all tests. RESULTS: Significant differences were found between the 1st quarter (GFT) and 3rd quarter (GTT) groups regarding mediolateral oscillation amplitude (GFT: 0.4 cm and GTT: 0.2 cm) and mediolateral displacement rate (GFT: 0.9 cm/s and GTT: 0.4 cm/s). There was a gradual decrease in anteroposterior and mediolateral oscillation rate, and in the speed of displacement from platform 1 to platform 2 in GFT. There was a significant difference in oscillation amplitude and mediolateral displacement speed between GFT and GTT. CONCLUSION: The variables analyzed showed minor differences and do not constitute an imminent risk for the stability dynamics of pregnant woman.