*^°Andrea A. Conti, *^Claudio Macchi, ^Raffaello Molino Lova, °§Antonio Conti.
*Dipartimento di Area Critica Medico Chirurgica, Università degli Studi di Firenze.
^Fondazione Don Carlo Gnocchi, IRCCS S. Maria agli Ulivi, Firenze.
°Centro Italiano per la Medicina Basata sulle Prove, Firenze.
§Dipartimento di Fisiopatologia Clinica, Università degli Studi di Firenze, Firenze, Italy.

Sir,
We have read with interest and attention and much appreciated the stimulating paper by G. Berthelot and co-workers (1).
Their scientific approach to such a social-health topic, as the frontier of physiological excellence performances in sports, is pertinent and well-taken.
We would like to expand this issue with original contributions to the discussion.
The model proposed is intriguing in its proposed ability to “foresee” future sports performances, but some methodological caveats are appropriate. The history of sports, in effect, teaches that not infrequently disciplines in which the limit (world record) has not been modified for years, if not decades, may be “suddenly” and notably improved. The case of the 200 metres (men) in athletics, with its world record unchanged for almost a generation (1979-1996), is paradigmatic, with an improvement of 0.4 seconds (19.32 versus 19.72 seconds), that is, more than 2%, occurring seventeen years after the previous world record (2).
Anthropometric changes, according to secular trends, are not the only reason for the improvement of individual excellence performances. The modification of training techniques and of agonistic materials, in addition to changes in regulations, play a major role in the achievement of world best performances, and in the future may be still predicted to do so even more.
Berthelot and colleagues conclude their interesting paper stating that their model “forecasts that human species’ physiological frontiers will be reached in one generation”. Rational estimations regarding the mean behaviour of a single biological parameter are possible, even if challenging. Predictions regarding an integrated set of human components leading to a whole psycho-physical top performance, as in sports world records, are far more difficult, and the history of sports medicine and, more in general, of mankind indicate how problematic reliable predictions are regarding excellent individual performances (3).

References
1) Berthelot G, Thibault V, Tafflet V, Escolano S, El Helou N, Jouven H, et al. The citius end: world records progression announces the completion of a brief ultra-physiological quest. PLOS ONE 2008; 3: e1552.
2) International Association of Athletics Federation. Available at: http://www.iaaf.org/index....
3) Cheuvront SN, Carter R, Deruisseau KC, Moffatt RJ. Running performance differences between men and women: an update. Sports Med 2005; 35: 1017-24.

Corresponding Author:
Andrea Alberto Conti, MD, MPH, PhD.
Dipartimento di Area Critica Medico Chirurgica, Università degli Studi di Firenze.
Viale Morgagni 85, I-50134, Firenze.
Tel.: +39-055-7949357;
Fax: +39-055-4378638;
E-mail: aa.conti@dac.unifi.it.