 THE PERFECTION POINT Predicting the absolute Limits of Human Performance by JOHN BRENKUS Macmillan ?12.99 pp260  aN OPTIMIST'S TOUR OF THE FUTURE by MaRK STEVENSON Profile ?12.99/ebook ?11.06 pp329  Predicting the future may be a fool's game, but the authors of these two infectiously enthusiastic books play it with gusto. Both are fascinated by the future limits of the human body. John Brenkus's hugely entertaining The Perfection Point sets itself the narrower task, seeking to discover how often world records can be broken before they break forever. Just how good, in other words, can athletes get?  It is the kind of engaging topic that has stirred up the public bar since Roger Bannister proved popular wisdom wrong by running a mile in under four minutes. actually, says Brenkus, the idea of a fourminute-mile "barrier" was just a myth put about by newspapers. This doesn't mean that there are no limits at all. Statistics show records falling by ever-smaller increments, so we are surely edging ever closer to the "perfection point" - the feat that can never be bettered.  Brenkus begins with Usain Bolt's blistering time for the 100 metres at the 2008 Beijing Olympics: 9.69sec. Then, with a deft hand for imparting suspense, he starts adjusting downward. First he improves on Bolt's "downright pedestrian" reaction time, then allows for the less-than-optimal wind speed and altitude. What if Bolt hadn't started showboating at the finish? What if he had been a bit older, and closer to a sprinter's career peak? What if his weight, height and strength had been nearer to sprinterly perfection?  a perfect 100-metre sprint, it seems, could be run - will be run - in 8.99 seconds, though it might take 900 years. More immediately, in the next 250 years or so, we'll see the mile run in 3.18.87 (almost exactly the same pace as won the 1925 women's 100-metre sprint), and a boggling 921lb benchpressed ("nearly the rated cargo-carrying capacity of a Ford F-150 half-ton pickup"). The chapter on the longest golf-drive (530 yards) gets sidetracked by the issue of equipment and regulations. But in one of his enjoyable fictionalised mini-scenarios, Brenkus conjures a champion Kenyan marathon runner in 2245, fleeing hostile soldiers and trying to make it 26 miles to the Tanzanian border. His time? - 1.57.58 - a staggering 6min off Haile Gebrselassie's current record.  British readers may yawn over the highest basketball dunk or furthest-hit home run, but the chapter on competitive breathholding (static apnea) is a winner - if only for revealing that such a sport exists. The record stands at 11min 35sec. In the distant future, that could be 14min 47sec.  During competition, we learn, breath-holders endure dreadful contractions and seizure-like fits known as "having a samba". Competitive self-destruction is, of course, the dark side of athletic boundary-pushing. Brenkus observes that male wheelchair athletes have boosted their blood pressure, and thereby their performance, by "using rubber bands to restrict output from their bladders" (he doesn't explain how). He believes that underwater swimming is not an Olympic sport because too many athletes would die trying. He deals with performance-enhancing drugs thoughtfully, but fails to consider a world where genetic and technological meddling are routine.  If Mark Stevenson's excitable an Optimist's Tour of the Future is to be believed, however, such a time is close at hand. Stevenson presents us with "a world where we start to have the same control over biology that we have over software". Tellingly, he finds this prospect thrilling. He learns that Skywalker-style artificial hands are already being wired into patients' nervous systems, that people are regrowing their own bones using stem cells and that, by the 2016 Olympics, if not before, paralympic athletes outrun the able-bodied, thanks to ever-more advanced prosthetic limbs.  More disturbingly, an Oxford "transhumanist" professor predicts that he, Stevenson, may live for thousands of years - as long as he can survive until the moment of "longevity escape velocity", that is, when medical advances increase life expectancy by more than a year for every year that goes by.  The problem with Stevenson's book, which is really the problem with the future, is that it is not mome ty", ces in ng ment ", an venson's Steve pr at discussnge, always clear when we're discussing real, imminent change, and when we're playing fantasy futures. In the latter two sections of his book, on non-biological technology and climate change, he claps eyes on real, present-day futuretech objects. He sees a working "spaceplane" in a hangar in the Mojave desert and "meets" a robot in the MIT Media Lab that can learn to push buttons by generalising from experience. He is given a list of currently available nanotechnology-based consumer products, including antimicrobial bandages, anti-odour socks, sunscreen and pregnancy tests. The Greeks are even working on a selfhealing anti-earthquake house using nanopolymer particles.  His journey into the environmental future feels almost like a different book, as the problem is all too clear and the solutions, on the whole, admirably practical. es. environst st bl i He calls in on living algae in a New Zealand municipal wastewater pond  