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Human growth hormone (GH) has a number of accepted medical uses, but has quickly become a popular ergogenic aid among athletes. The issue of performance-enhancing substances such as anabolic steroids and GH has drawn the attention of athletes, their parents, and politicians. On almost a daily basis, headlines about the status of doping in professional, international, and amateur sports seem to be more pervasive. The supraphysiologic effects of GH lead to lipolysis, with increased muscle volume. Due to the ethical limitations of studying the use of high doses of GH in isolation or combined with anabolic steroids, the scientific literature has not produced compelling results on its efficacy. GH has potential as an anti-aging drug and does lead to some improved athletic performance in isolated studies. Despite the lack of compelling data, GH seems to have developed a reputation among athletes for enhancing performance. The detection of illegal doping with GH has been the focus of a concerted international effort by the International Olympic Committee. A number of promising detection techniques may allow the detection of illicit GH use. This review on GH as an ergogenic aid includes a discussion of the basic physiology of GH and its actions, the accepted medical indications for its use, the results of scientific studies that assess whether it improves exercise performance or work capacity, and the scientific techniques under development to detect ergogenics with strong abuse potential.

Letting (T(t): t ⩾ 0) be a strongly continuous semigroup of contraction operators on L1(X,M,λ) we consider the question of the almost-everywhere convergence of (1α) ∝0α T(t)ƒ dt as α → 0 + (the local ergodic theorem). The limit is known to exist in the case where the semigroup is positive. In this paper we consider the question for general semigroups which may contain nonpositive elements. We show that a maximal ergodic inequality is equivalent to the local ergodic theorem. We also present some extensions to the local ergodic theorem. All the results of this paper also hold for N-parameter semigroups.