Caffeine gum improves 5 km running performance in recreational runners completing parkrun events.

Purpose: The purpose of this study was to determine whether caffeine gum improves the performance of recreational runners completing parkruns (weekly, 5 km, mass participant running events).

Methods: Thirty-six recreational runners (M = 31, F = 5; age 33.7 ± 10.

Representational demands in mothers' talk to preschool children in two contexts: picture book reading and a modelling task.

Shared book reading is considered to be an influential factor in language and literacy development and has been associated with more complex and demanding forms of tutorial language use. The present study seeks to examine mothers' discourse in joint picture book reading in terms of the level of representational demand which it places on the child, that is the extent to which it requires the child to engage in abstract thought. This was compared with the language used in another interactive, but more product oriented task, modelling a clown using play-doh.

Steiger on refraction: a reappraisal.

Seventy years ago Steiger, a Swiss ophthalmologist, found the distribution of corneal powers to follow a normal (binomial) curve. He noted a wide range of values among emmetropes, and he also knew that their axial lengths varied significantly. He expected that normal distributions would be found for other components of refraction and also for refraction as a whole, and in seeking a controlling mechanism he recalled the multifactorial pattern of inheritance of such characteristics as stature.

Modes of inheritance of errors of refraction.

Eighteen families in which both parents had refractions within the range of +4·0 D to −4·0 D and axial lengths seen in emmetropia (22·3-26·0 mm) showed coefficients of correlation of the order 0·5 indicative of polygenic inheritance. Such coefficients were seen for axial length (0·407) and for the cornea (0·487), but not for the lens (which is known to be yoked to the axial length). No such coefficients were seen in 19 families in which one of the parents had axial length outside the emmetropic range (nine families with long axes and 10 with short axes).