Something about this week’s sudden onset of blue skies and bright sunshine reminded me of warm weather training in Tempe, Arizona. When, during college spring break, the entire track and field team would decamp from the still wintry New England coast to the searing desert city suburb.

There was training in the morning and late afternoon, at Sun Angel Stadium, the rest of the time spent lounging around the hotel pool. From day one the sprinters and hurdlers, ripped to the core, had their T-shirts off, and the throwers, although more fleshly than burly, soon followed suit.

Zero body fat

We distance runners, all ribs and bony shoulders, always kept the T-shirts on, and not because of vanity: every ounce of that cotton, even in the deadly heat, counted against our close to zero body fat.

We were the envy of nobody, until it came to all-you-can-eat hour at Samson’s Diner. The unbearable lightness of being a distance runner still allowed for a good feed and a good few beers, especially with a 20-miler the next morning. Our only worry then was getting injured, which meant we didn’t eat anything at all.

It’s no secret that weight has always been a heavy issue for athletes, and, it seems, increasingly so. Nothing beats being lean and mean, not just in distance running: cycling, swimming, rowing, and most endurance-based events put a strict limit on excess baggage, creating a sometimes dangerously fine line between the fuel supply and fuel demand. Because ideal body weight, as much as talent or skill or the so-called 10,000 hours of practice, can ultimately make the difference between winning and losing.

This will be evident across all sporting arenas this weekend – although the problem in some cases is defining “ideal” body weight. It’s okay for most GAA and rugby players with their cupboards full of baked beans and protein powders, where the scales can always swing a little. It was interesting too to hear Tiger Woods compare this weekend’s US Masters to his first victory in 1997, when “nobody worked out except for Vijay [Singh] and myself” – while now “you see guys are losing weight, getting fit faster, doing things people thought was unheard of in our sport”. Not that any golfer will ever win a green jacket on body weight alone.

Then there was Andy Lee’s so-called title fight. He’d been trimming away at every spare ounce of body fat ahead his WBO middleweight defence in New York, to weigh in under the limit of 160lb (or 11st 6lbs, in old money). Only his opponent, the Cuban-American Peter Quillin, weighed in 1.4lb over that limit, and failed to shed that weight in the allocated two-hour leeway. So the fight will no longer be a title fight. Although while most boxers struggle in some way to “make” the weight, at least it’s for one night only – before they go off for a good feed and a good few beers.

No such joy for the 39 jockeys riding in the Grand National at Aintree, the unbearable lightness of which was laid bare this week by Ryan Mania. In a far from pretty interview with the Guardian, Mania talks about the desperately strict diet required to maintain his riding weight – or rather underweight. "As a jockey, you have no life," he says. "Everything is based around keeping your weight down. But no nutritionist is going to fix that when your body has to be two stone lighter than it wants to be."

Eventually, no longer able with stand the “grumpy, miserable bastard” he had become, Mania retired, last November. Now out of saddle, he also points the finger at pressures within the profession: “There’s a lot of time that I could have turned around and said to the trainer or the owner: ‘Look, I can’t move that weight, I can’t ride that horse.’ But if you turn that race down, you might lose other rides because of it.”

At 5ft 11in, Mania was always fighting a losing battle against near emaciated weight (even with the 10st minimum for jump jockeys), and so too it seems was Joseph O’Brien. This week, O’Brien lost his spot as number one flat jockey at his father Aidan’s stable at Ballydoyle to Ryan Moore, not that he’s carrying much extra weight. But at age 21, and just under 6ft, O’Brien has outgrown himself in a way only jockeys can understand: at 9st 5lb he’ll never ride the Classic weight of 9st again.

Unattainable weight

So, after riding two of the past three winners of the Derby for his father, O’Brien junior is reluctantly off to the hurdles.

Both Mania and O’Brien went into the jockey business knowing all this and Mania also offers a nice reminder of missing the buzz, and that “if I was naturally 10 stone every morning, I would never have retired”.

It’s also a reminder that while some people like to take a stand against the Grand National for putting the horses health at risk, perhaps they should spare a thought for the jockeys, who endure their unbearable lightness without ever being allowed a good feed and a good few beers.