So what is the solution for muscle fatigue? I'm assuming you'll say plenty of rest and sleep.
Sleep, hydration and diet are the main things in the short term.
There are lots of claims (possible true to some degree and in extremes) about fancy muscle shakes and protein bars. Unless you are really pressed for size and weight for carrying, for instance you're doing a mountain marathon, then they're probably not worth it. Instead look to up your carbs over the days before to ensure plenty of glycogen is stored in your body (one of the substrates I mentioned earlier). Keep up a balanced diet full of protein, fruit and veg. One of the main things protein products provide is casein, which is a readily-absorbed phosphoprotein - but remember this is present is decent quantities in meat, dairy products and pasta, so just include them.
Keep topping up during the day of the walk. Also drink enough. In extreme cases of heat or exercise you might want to consider electrolyte-rich drinks (or include sugary and salty snacks in your food).
Now, if you want to get a bit more serious about it, consider your clothing. Muscle compression is now a big thing in sport because it allows the athletes to perform for longer. It really works. Running 10km across the fells in compression leggings and my legs are a little tired, I actually fail in the lungs before the legs (my asthma). Doing the same route in loose trousers and my calves and thighs are burning out by the end.
The difference isn't as easy to notice in walking, but after a day wearing tight calf socks I feel fresher than wearing loose socks.
Then there's warming-up. Not something we every really think of doing as walkers. But perhaps we should - certainly if pushing our limits physically.
In extremis, you could use anti-inflamatories such as ibuprofen. But, seriously, only use drugs to get you out of trouble - perhaps a case where its a choice between popping a couple of ibuprofen or dialling 999.
There are some foods with anti-inflammatory effects. Unfortunately, most of the guidance on diet in that regard contradicts the needs for high carbohydrates needed for the energy for a hard walk. If this is something you want to consider, look at Omega 3 (not 6) and olive oil, along with the classic antioxidants like VitC.
That's pretty much it for a day walk. But what about the next day? Well, there are some tried-and-tested ways to reduce the longer-term effects of muscle fatigue.
The most effective is the most unpleasant - the ice bath. One of the fixtures at Selection is an inflatable paddling pool behind the medical centre that's filled with iced water each afternoon. Now, I'm not proposing that outside of serious competition. But cold-showering the legs, or paddling in a river are more pleasant alternatives.
Then there's stretching, and the modern trend of rollering, immediately after exercise.
Finally, the nicest but often least practical - getting a massage.
Longer-term, the big thing is training your body correctly. If you want to walk for a whole day in the hills, don't exclusively run 100m sprints. I see so many fit young people flop after a couple of hours because their whole training has been based around 45mins each way. This isn't just a psychological thing - it is to do with the ratios of different types of muscle fibres, metabolic rates, and so on.
