I remember back in the 90's, players used to retire fairly early, notably China players retiring at 27 year old or so. Now, even the China players are extending their careers to 30 years old. The reason? Better prize money? Lack of competition?
Maybe it has to do with badminton specifically. In some sports/competitions, being older than 27 is a huge disadvantage (because some rely almost exclusively on physical fitness). But in badminton there's a combination of fitness and skill so as you get to your 30's, you're probably more technically skilled even though your body is starting to slow down. That would be my guess.
maybe tougher training regime (increased usage of technology?) at a younger age so body of a 30 yr old professional player can withstand more stresses and play at a faster pace yet longer than one 10-20 years ago, diet, better equipment (more supportive footwear, lighter rackets), more efficient movement and energy usage (breathing?) And maybe being a little more selective at which high profile tournaments to play at
I think it is because today there is a lot more knowledge about how to keep the body more or less healthy while being a professional athlete. A few years ago you would rarely do prehab meaning that if nothing hurts you wouldn't invest time in massages or physio work. Also I think that weight training wasn't used as much back in the day. That also has a positive effect on your joint and muscular health.
i think that's the key. in other endurance sports, people are just about their best in their early 30's. the current reigning Olympics Marathon gold medalists is 31yrs old, silver 26, bronze 30. Mo Farah who has a double double 10k/5k Gold in Rio/London is 33 yrs old, Usain Bolt is 30! endurance doesn't go down that much going into the 30's, but the recovery time does. a lot more focus has been made on how to recover quicker. badminton is particularly worse as there are matches on consecutive days. runners has it easier as they have weeks to recover. worst is cyclist in a multi-day/week tour, who has barely any time to recover from a 5 hours stage. but the idea is the same, ice, massage, compression, nutrition.
I don't think players retire earlier before. For example, BCL and CJ retired in their twenties. But MF, Kenneth Jonassen and Wong CH well in their thirties. Park from Korea MS also in his twenties. Well, there are so many cases, it is difficult to get a precise idea.
I think phili has a point. I remember in the 80s - around the same time the 90s pros were coming of age - coaches in various sports suddenly told us certain stretches had been deemed dangerous - things like hurdler's position and rolling ankles. These were still getting used by some coaches here in the 90s, though not necessarily badminton. I'm sure smarter training has contributed. In terms of badminton and more specifically men's singles, I'm sure there was some kind of gilded age of players mostly born in the early 80s or slightly before. I mean, you had that generation from Gade to Chen Jin where all those guys won major titles before age 21, then for the 8-year period between Chen Jin and say, Axelsen-Momota, you had no one but Chen Long making a mark by age 20. Now, of course, Sugiarto and Son, etc. are in the top 10, in their late 20s but they didn't have the same prodigy period. Also, is it the average or the maximum that has gone up? Perhaps in the 90s, no one kept going this late but still today, for every 36-year-old Cai Yun, you have plenty of top players who retired much earlier, some of them long before age 30. Bao Chunlai (28), Chen Jin (27), Du Pengyu (26), Guo Zhendong (29), Xie Zhongbo (26), Shen Ye (26), He Hanbin (26), Zheng Bo (27). And maybe it's just a Chinese thing. The Danes have always stayed on longer, I believe. The Koreans haven't changed a bit. Bae Yeon Ju is retiring slightly younger than Bang Su Hyun did and only a little older than Jun Jae Youn and Hwang Hye Youn. The 3 Lees - Kyung Won, Hyo Jung, and especially Hyun Il - lasted longer than the average but Park Sung Hwan, Cho Gun Woo, Hwang Yu Mi, Lee Jae Jin, Hwang Ji Man, Kwun Yi Goo, Ha Jung Eun, Kim Min Jung all retired long before age 30.
There is very good money at the top level, worth playing on for than retiring to your own business for.
