Sleep is essential to both performance and progress. Not getting enough of it affects your efforts to build muscle and lose fat – not to mention your general health and happiness. If you're struggling to get enough shut eye, the Indian herb ashwagandha has been found to be highly effective at inducing sleep. Just one dose of 300mg extract twice daily has been shown to reduce both the time taken to drift off and the quality of sleep. On the back of such findings, sales in the US grew a whopping 165.9 per cent last year.