What they ^^^^ said. Drink lots of fluids - at least 2litres of water per day. Look for "rehydrate" powders in supermarket/chemists and take one a day in water.
Morrisons are doing "For Goodness Shakes" recovery drinks half price just now, tho' there were recent tests which concluded old-style "drinka-pinta-milk" was just as good for after exercise.
You need more carbs and more water. Carbohydrates swell your muscles so they can absorb and store more fluid. Obviously, you need more water to take advantage of that fact. Milk is good because it's full of good stuff. It's mostly water but has carbs and protein - for energy and muscle repair respectively. Milk should be a staple of any postman/postwoman's diet. I only drink milk when I'm on delivery.
I get this (normally after a heavy day) when i get out the bath after work.
I would agree with the fluid intake.
Never used to get it at all till we hit 4hrs
Rows of houses all bearing down on me........I can feel their blue hands touching me.......All these things in all positions.........All these things will one day take control..........
Any low GI carbs like oats, fruit, nuts, will serve you well. Problem is your body will need to be replenished, not so much before but during and after. Hydration in unexpectedly hot conditions is something you need to be aware of in advance. If you know it's going to be hot tomorrow, for instance, get plenty of carbs and water down you the day before. Try to steer clear of stuff like coffee. If you eat crappy cereals* like Corn Flakes, sort your life out. Porridge is the boss.
It could also be you have a knee or back injury and your hamstring (the muscle behind the thigh) is having to do extra work to compensate.
It is telling you it isn't happy.
The societies of consumption and squandering of material resources are incompatible with the idea of economic growth and a clean planet.
I always take a half teaspoon of salt in the mornings during the hot weather, works a treat, but again, plenty fluids. Some of the baby re-hydrate stuff works well too!