Electrical impedance myography (EIM) is as an experimental technique that associates muscle impedance with muscular activity. Changes in muscle impedance during contraction occur mainly due to changes in the morphological and physiological characteristics of muscles that lead to different impeditivities in comparison with the resting condition. There is no consensus on the details of muscular impedance during muscle activity. EIM measurements on humans are also influenced by factors such as the electrode–skin interface, layers of skin and fat, and the connective tissue that can generate undesirable effects in the impedance signal. These effects can be avoided if EIM measurements are carried out directly on the muscle by using the models of animals. This study investigates changes in the EIM signal in the gastrocnemius muscles of Wistar rats during different levels of muscular contraction. In vivo experiments were conducted on 19 male rats. The muscle was exposed, fixed on a load cell, and electrically stimulated to evoke different levels of muscle contraction. Signals of the components of impedance were analyzed against the muscular force signal. The results show moderate correlations (p < 0.05) among the impedance-related parameters of resistance (r = −0.76), reactance (r = 0.57), and phase (r = 0.53). In addition to providing an experimental protocol for the invasive collection of data on electrical impedance to minimize problems associated with surface electrodes, this study shows that of the components of impedance, resistance is most affected by the intensity of muscular contractions and that morphological changes influence impedance mainly at low intensities.

Background: Currently the resistance training (RT), is considered a contributor to improved mental health, however, is not reported in the literature an frequency ideal of training. Purpose: The purpose of this study was to assess the impact of the practice of RT on the psychological health of employees participating in a corporate wellness program, in different numbers of weekly sessions (2, 3 and 4 times), for a total of 12 weeks. Methods: 77 individuals were selected; 33 women and 44 men, between the ages of 30 and 45, employees participating in a corporate wellness program. The individuals were randomly divided and classified as control group (n=10) and three more groups (G2,G3, and G4), according to weekly training frequency. The groups followed RT programs made up of eight exercises with medium intensity of 10RM for 12 weeks. The General Health Questionnaire with 12 items (GHQ-12) was applied before and after the intervention period. The GHQ-12 results were calculated using the Likert scale format. Results: Significant statistical differences were noted between pre and post-intervention periods in all groups, indicating improvement in psychological health, most noted in G4. Conclusions: The data revealed that RT is capable of improving mental state in its practitioners after three months of training and that weekly frequency has little influence in this improvement, even though the group that trained with more frequency presented slightly higher levels of improvement in psychological wellbeing.

Lactate threshold (LT) is one of the physiological parameters usually used in rowing sport training prescription because it indicates the transitions from aerobic to anaerobic metabolism. Assessment of LT is classically based on a series of values of blood lactate concentrations obtained during progressive exercise tests and thus has an invasive aspect. The feasibility of noninvasive LT estimative through bioelectrical impedance spectroscopy (BIS) data collected in thigh muscles during rowing ergometer exercise tests was investigated. Nineteen professional rowers, age 19 (mean) ± 4.8 (standard deviation) yr, height 187.3 ± 6.6 cm, body mass 83 ± 7.7 kg, and training experience of 7 ± 4 yr, were evaluated in a rowing ergometer progressive test with paired measures of blood lactate concentration and BIS in thigh muscles. Bioelectrical impedance data were obtained by using a bipolar method of spectroscopy based on the current response to a voltage step. An electrical model was used to interpret BIS data and to derive parameters that were investigated to estimate LT noninvasively. From the serial blood lactate measurements, LT was also determined through Dmax method (LT). The zero crossing of the second derivative of kinetic of the capacitance electrode (Ce), one of the BIS parameters, was used to estimate LT. The agreement between the LT estimates through BIS (LT) and through Dmax method (LT) was evaluated using Bland-Altman plots, leading to a mean difference between the estimates of just 0.07 W and a Pearson correlation coefficient r = 0.85. This result supports the utilization of the proposed method based on BIS parameters for estimating noninvasively the lactate threshold in rowing.

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