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Electromechanical delay of abdominal muscles is modified by low back pain prevention exercise

Szpala A., Rutkowska-Kucharska A., Drapala J.

Acta of Bioengineering and Biomechanics

2014

Vol. 16, no. 3

95--102

The objective of the research was to assess the effect of a 4-week-long training program on selected parameters: electromechanical delay (EMD) and amplitude of electromyographic signal (EMG). Fourteen female students of the University School of Physical Education participated in the study. Torques and surface electromyography were evaluated under static conditions. Surface electrodes were glued to both sides of the rectus abdominis (RA), external oblique (EO), and erector spinae (ES) muscles. The 4-week-long program was aimed at strengthening the abdominal muscles and resulted in increased EMD during maximum torque production by flexors of the trunk, increased amplitudes of the signals of the erector spinae (p = 0.005), and increased EMG amplitude asymmetry of the lower (p = 0.013) and upper part (p = 0.006) of the rectus abdominis muscle. In a training program composed of a large number of repetitions of strength exercises, in which the training person uses their own weight as the load (like in exercises such as curl-ups), the process of recruitment of motor units is similar to that found during fatiguing exercises and plyometric training.

Study of lead-free solders liquidus and solidus temperatures by means of DTA-method

Docekalova S., Smetana B., Drapala J., Perinova K.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

2007

Vol. 321, z. 89

99-99

The thermal analysis is very effective tool in the study of thermophysical and thermodynamical properties (e.g. temperatures of phase transformations, latent heats -enthalpies of phase transformations,...) among others, metallic systems. One of the most widespread methods of thermal analysis used for the description of metallic systems behaviour is the Differential Thermal Analysis - DTA. The aim of our work was study of characteristic phase transformation temperatures (temperatures of solidus - T$ and liquidus - TL) of lead-free solders on the base of tin. In total 22 alloys with different ratios of individual elements Ag, Cu, In, Sb, Bi, Zn and Sn were prepared experimentally. In addition, six alloys of lead-free solders produced commercially (Kovohute Pf ibram) were used and the Pb-Sn solder served as a comparative alloy. The alloys were prepared by smelting of input metals in the graphite crucible followed by casting into graphite boat. Temperatures of solidus and liquidus were obtained with use of experimental laboratory system SET ARAM SETSYS 18TM TG/DTA/TMA. Samples of solders in the form of small disordered pieces (size up to approx. 3 mm and max. mass 0.2 g) were during measurement heated and cooled in a controlled manner at the rate of 4°C/min. The A12O3 crucibles were used for measurement. Argon (purity > 99.999999%) was used for washing of the inert space of oven before each analysis (flow time approx. 15 min), then evacuation followed and again filling up with argon. During analysis the constant dynamical atmosphere was kept in the oven space (flow rate of argon was 2 1/h). Differences between experimentally determined temperatures of Ts, TL acquired during controlled heating and cooling were observed. These differences could be influenced not only by undercooling, but also by dynamics of measuring process.