Looped Elastic Resistance during Squats: How Do Band Position and Stiffness Affect Hip Myoelectric Activity?

Looped elastic bands around the thigh are commonly used during squats and result in increased hip activation. Due to the closed kinetic chain nature of the squat exercise, one may expect that placing the elastic band on distal segments, close to the floor contact, may not result in the same increase in hip muscle activation as that achieved with a looped band around the thigh. We analyzed the effects of band position (thigh, lower leg, and forefoot) and band stiffness on the myoelectric activity of the tensor fascia latae, gluteus medius, gluteus maximus, biceps femoris, vastus medialis, and vastus lateralis during squats in 35 healthy subjects (18 men and 17 women). The greatest myoelectric activity of hip muscles was observed when the stiffest band was positioned around the forefeet with an increase in 24% for the tensor fascia latae, 83% for the gluteus medius, and 68% for the gluteus maximus compared to free (without resistance band) squatting. Contrary to previous thinking, the use of elastic bands around the forefeet during squats can elicit increased myoelectric activity of hip muscles, with a magnitude often greater than when the band is placed around the thigh segments.

A non-mercury electrode for the voltammetric determination of butralin in foods.

A modified electrode was developed with Co-Ag bimetallic nanoparticles stabilized in poly(vinylpyrrolidone) for butralin monitoring. This is the first non-mercury electrode proposed for the quantification of butralin. The bimetallic nanoparticles were characterized by spectroscopic and microscopic techniques, which showed that they are composed of a cobalt core partially covered with silver. The modified electrode was characterized by field emission gun scanning electron microscopy, energy dispersive X-ray spectroscopy and electrochemical impedance spectroscopy. The experimental parameters (pH, supporting electrolyte, accumulation step, pulse technique) were optimized. The calibration plot for butralin obtained by square wave voltammetry was linear in the range of 0.1-1.0 µmol L-1 with limits of detection and quantification of 32 and 106 nmol L-1, respectively. Lastly, the modified electrode was effectively implemented in the quantification of butralin in honey and apple jam samples. The results were in agreement with those furnished by UV-vis spectrometry and endorsed by statistical tests.

The effects of predictive trials on critical stroke rate and critical swimming speed.

BACKGROUND: Critical swimming speed (CSS) and critical stroke rate (CSR) have important practical applications in evaluating endurance capacity and stroke parameters. The CSS and CSR are determined from the linear regression between two or more performance times with the respective predictive distance or "number of stroke cycles," respectively. It is already known that CSS is dependent on the number and duration of the predictive trials chosen, and performance times ranging from 2 to 12 min have been recommended. However, the effects of predictive trials on the CSR have not been reported. It was hypothesized that CSS and CSR determined by different predictive trials lasting 2 to 12 min would elicit similar values. Therefore, the purpose of the present study was to determine the impact of different combinations of predictive trials lasting 2 to 12 min on both CSR and CSS. METHODS: Thirteen swimmers performed three fixed-distance (200, 400, and 800 m) performances. All possible combinations of CSR and CSS with two (CSR200-400/CSS200-400, CSR200-800/CSS200-800, CSR400-800/CSS400-800) and three (CSR200-400-800/CSS200-400-800) trials were determined. RESULTS: No significant differences were found between CSR and CSS determined with different predictive distance tests. In addition, CSR200-800 and CSS200-800 showed the lowest coefficient of variation and highest intraclass correlation coefficients with CSR200-400-800 and CSS200-400-800, respectively. CONCLUSIONS: This study demonstrated that CSR and CSS were not statistically different when determined with different predictive trials located within the recommended durations of 2-12 min. Nevertheless, CSR200-800 and CSS200-800 exhibited the best consistency with CSR200-400-800 and CSS200-400-800, respectively.