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Investigation of mutual aerobic and lower limb muscular activity during cycling

Griskevicius P., Daunoraviciene K., Pauk J., Troskovas V.

Acta of Bioengineering and Biomechanics

2015

Vol. 17, no. 2

109--118

The evaluation of physical activity is a complex task that requires performing an analysis of muscular activity and aerobic/anaerobic threshold and it is often difficult to observe and propose a single method. The purpose of the article is to evaluate a relation between aerobic capacity and activity of lower limb muscles via changes of muscle’s EMG signal during physical, sub-maximal veloergometric loading. The activity parameters of 5 lower limb muscles such as semitendinosus, rectus femoris, biceps femoris, gastrocnemius medialis, and tibialis anterior were measured and analyzed during the veloergometric exercise tests and the heart rate and the aerobic capacity were estimated from registered data. The obtained aerobic parameters allow setting an individual and overall voluntary physical capacity. The regression oxygen function presented allows analyzing and predicting the ability of subjects to generate energy while maintaining muscle activity during the exercise. The correlation between the consumption of oxygen and constant physical loading time is determined. It was found that comparing VO2max capabilities the physical effort in the male group was 16% higher than in women. Oxygen consumption and maximum muscle effort dependency on the load time was established. It was observed that the maximal muscular effort appeared before VO2max reached maximal limit in both groups. The maximal oxygen consumption is achieved in the middle or sometimes at the beginning (depending on load) of exercise while maximal muscular effort was found in several phases of cycling: at the beginning and at the end of loading time.

Pyro-adaptive impact energy absorber

Ostrowski M., Griskevicius P., Holnicki-Szulc J.

Journal of KONES

2007

Vol. 14, No. 1

303-309

The paper contains a proposal of energy dissipation density controlling in lightweight thin walled structures by reducing their crushing stiffness during an impact process. For small scale laboratory experiments, low-energy-dissipation absorber was developed. Prismatic absorber made of thin lead sheets can dissipate the impact energy at two energy density levels. Moving the concept to the real steel or aluminum structures can lead to satisfying value of the Specific Energy Absorption indicator with possible control of the energy dissipation. Experimental and FE explicit simulation results showing controllable impact process of a thinwalled prismatic absorber with rectangular crossection are presented. The control of crushing forces proved to be possible and efficient. Adaptivity ratio achieved in the presented example was 35%. The idea of the presented absorber was based on automotive front rail shape. The experimental tests have to be re-conducted. Geometry of the tested absorber should be modified to facilitate the detachment process of the stiffening members.