Since I turned 50 two years ago, I must begrudgingly admit that after playing hard for about 20 minutes, I'm fairly exhausted. I can still play, of course, for another hour or so (two hours is pretty much my limit), but the spring in my step is definitely gone by the 20-minute mark. Not long ago, it would take me about an hour to get to this stage. When I'm not playing tennis, I run 3-5 miles twice a week, so I get a decent amount of cardio.
I don't eat anything while I play tennis -- I've never done that. Is it time I start eating those gel packets or something? Advice would be welcome, though if the advice consists of playing doubles or pickleball, you can bet those will be summarily dismissed.
I'm over 50, play 7-10h/w (about 90m/session)
things i did/do:
* lose weight (dropped ~50lbs)
* reschedule recovery
* elim long runs (if anything, add short sprints, and don't even need that many reps... more useful for tennis anyway)... i would only do long runs as a precursor to getting my ligaments&tendons ready to do the real work of short sprints... also find that after 50, i needed to take a day to recover from say a 5M run, before trying to play tennis.
* do more tennis... movement patterns&muscles used are different than running, so your "tennis muscles" are not trained well (eg. capillaries not developed, etc...), and probably consume more resources (o2, glucose, etc...) and rid less waste (eg. lactic acide buildup)... running is very linear, and overdevelops the "forward movement" muscles.
* i've been doing intermittent fasting, with occasional longs fasts... i have often gone 24h without eating, and able to play 2h, but i think my body is "fat adapted"... but before that i did feel i needed "sugar shots" (eg. gel packets, gatorade, etc...)
* i drink alot of liquids + add LMNT or similar (electrolyes - aka salt = potassium/sodium -> fuel of potassium/sodium pump)... i read somewhere that potassium or sodium deficiencies can lead to muscle fatigue (due to reduced efficacy of the potassium/sodium pump in muscles)... no idea if that is key to preventing, but it works for me. fyi - a banana is not enough potassium, and probably too much sugar
my .02