Yeah, I get that too. After harder workout rides and runs I'll take a few supplements:
- Magnesium (mag lactate works best for me, but others are okay). Helps with twitchy muscles and even some spasms.
- Melatonin to help sleep. The body produces it naturally, but less efficiently as we age. Dosage varies, partly due to physical differences, partly because it's unregulated and concentration varies a lot. With some brands 1-5 mg is plenty; with others, it may take 20 mg or more to get the same effect.
- GABA, an amino acid that helps calm the nerves -- I don't mean "calm the nerves" in the psychological sense, although some folks find it helps reduce anxiety. I mean it literally seems to desensitize the nervous system. If I take too much I'll feel sluggish for a day or two. I bought some 500 mg capsules recently and those are way too strong for me. I'd do better with 50-100 mg. On the plus side it's almost as effective as my prescription muscle relaxers. (GABA is chemically related to prescription gabapentin, but not a replacement or substitute for the prescription med.)
- Vitamin D (actually a hormone) may help some folks recover from hard workouts. I take about 5,000 IU a day since my thyroid/parathyroid was removed, which messed up my body's vitamin D, calcium and bone density. Most normally healthy and active folks probably get enough vitamin D from a normal diet, maybe a multivitamin, and regular exposure to sunlight.
Soaking in a hot bath with Epsom salts helps too. (But don't take Epsom salts orally unless you're in the mood for flushing out your bowels -- it's a potent laxative, fast and nearly explosive. Stay very near a toilet after taking Epsom salts as directed for a laxative effect. So don't drink the bathwater.)