Zero-inflated Poisson regression models for QTL mapping applied to tick-resistance in a Gyr x Holstein F2 population

Nowadays, an important and interesting alternative in the control of tick-infestation in cattle is to select resistant animals, and identify the respective quantitative trait loci (QTLs) and DNA markers, for posterior use in breeding programs. The number of ticks/animal is characterized as a discrete-counting trait, which could potentially follow Poisson distribution. However, in the case of an excess of zeros, due to the occurrence of several noninfected animals, zero-inflated Poisson and generalized zero-inflated distribution (GZIP) may provide a better description of the data. Thus, the objective here was to compare through simulation, Poisson and ZIP models (simple and generalized) with classical approaches, for QTL mapping with counting phenotypes under different scenarios, and to apply these approaches to a QTL study of tick resistance in an F2 cattle (Gyr x Holstein) population. It was concluded that, when working with zero-inflated data, it is recommendable to use the generalized and simple ZIP model for analysis. On the other hand, when working with data with zeros, but not zero-inflated, the Poisson model or a data-transformation-approach, such as square-root or Box-Cox transformation, are applicable.

Electromyographic validation of the trapezius and serratus anterior muscle in pull-over exercises

The electromyographic activity of the trapezius and serratus anterior muscles was studied in 24 male volunteers during pull-over exercises. In 54.2 percent of the cases, the activity of the trapezius varied from weak to strong. In the remaining cases, as well as in pull-overs done with the arms bent, this muscle was inactive. Thus, the trapezius acts preferentially in pull-overs, but its variable levels of activity do no justify its inclusion in programs of physical conditioning. The serratus anterior had levels of activity which varied from weak to very strong in pull-over exercises. In pull-over with bent arms, this muscle showed very strong activity in almost half of the cases, thus justifying its inclusion in basic exercises in programs for physical conditioning. When conditioning the serratus anterior muscle using pull-over exercises with bent arms, the execution should not exceed the half way point of the return movement.

Electromyographic validation of the trapezius and serratus anterior muscles in supine and frontal elevation exercises

The muscle activity developed by the trapezius (upper portion) and serratus anterior (lower portion) muscles in three modalities of supine exercises executed with two grips (open and middle), was compared with three modalities of frontal elevation in 24 male volunteers 18 to 25 years old. The trapezius muscle acted preferentially in all frontal elevation modalities and not in supine exercises. The serratus anterior muscle acted more significantly in frontal elevation exercises than in the supine horizontal and inverted plans with both grips, but there was no significant difference in the responses to frontal exercises and supine exercises in the inclined plan.