The countries who regularly top the medal table spend millions on training and developing athletes, money that poorer countries simply can't afford to spend on their sporting stars.
Kenyan athletes exercise in the early morning near a high-altitude training camp.
With weeks to go before the Olympics, it's unlikely Kenya will be sanctioned over fresh doping claims. No matter what happens, a shadow will be cast over the integrity of the country's athletes.
Using our heads. New ways to battle doping in Olympic year.
The ban on Russian athletes at the Rio Olympics feels like a victory, but it masks an insular system which is spread too thin.
It all got a bit too much for Wales fan Jamie Collins.
Football, cricket, athletics, rugby – whatever the sport, the tears are never far away, for both the stars and the spectators.
Caster Semenya was withdrawn from competition in 2009 on the basis that her higher-than-normal testosterone level conferred a performance advantage.
Until recently, women with higher-than-expected testosterone levels were declared ineligible to take part in track and field athletics.
On their knees. Scrutiny and stigma for athletes has ramped up.
The history of the fight against drug taking in sport shows us why we're in such a mess right now.
The Southern Stars celebrate winning the Royal London One Day International Series in 2015.
There's been plenty of commentary about Novak Djokovic's recent remarks on women's bodies and the pay gap in sport. He's right that men and women are different – but female athletes are working a lot harder.
Easy to remember how to do, hard to figure out how it’s working.
What does it take to keep a bicycle upright and moving, without crashing?
Born this way.
The IOC's changes to transgender policy is useful, but the situation is still complicated.
The rebrand awaits.
Why Adidas pulled its sponsorship of the IAAF, the governing body of world athletics.
WADA chief Dick Pound speaks to journalists at the launch of the latest anti-doping report.
Fresh details about the findings of the World Anti Doping Authority raise questions about athletics chiefs.
The long road to reform awaits.
How athletics can and must deal with the doping scandal that threatens the sport's legitimacy.
The “Armstrong era” forced cycling into deep soul-searching.
A massive doping problem in the Lance Armstrong era has inspired some useful reform ideas, but governance issues must be solved as well.
A damning report exposes doping and corruption at every level. And the Russians aren't likely to take the fall for everyone.
Is WADA an appropriate body to be entrusted with the sole authority to investigate doping in sport?
Proposed changes to anti-doping are likely to increase WADA's powers, but in the search to detect doping athletes, the innocent are likely to be punished along with the guilty.
Feet to the fire. Is athletics going the way of cycling?
Where can sport go when performance-related doping always seems one step ahead? The WADA report should open the door to a more rational future.
Stefanie Reid was a standout at the 2012 games.
Paralympic athletes are representing in Doha, while back home the welfare state is being attacked.
Mo Farah has said he wants to give back, but what about the system?
Without addresses inequalities in sport and diversifying funding, there will always be a problem in getting ordinary people interested in sport.
Hold your breath.
Ng Han Guan/AP/Press Association Images
The poor air quality at major sporting events can have a damaging affect on athletes' performance and health.
Level playing field?
The current anti-doping regulation clearly isn't working. Perhaps it is time to change our approach.