Yoga and meditation - can Christians practice them

Take the two words apart. Meditation itself is commanded in Scripture - but notice what kind: biblical meditation is filling the mind, not emptying it. 'In his law doth he meditate day and night' (Psalm 1:2); 'I will meditate in thy precepts' (Psalm 119:15).

Slow, repeated, prayerful chewing on God's Word - and quiet stillness before him ('Be still, and know that I am God', Psalm 46:10) - is a neglected treasure Christians should reclaim without embarrassment. Mindfulness-style techniques for calming the body (breathing, noticing, slowing) are, in themselves, no more spiritual than exercise; used to quiet an anxious body while the mind rests on Christ, they can serve you (Philippians 4:8). Yoga is where discernment is needed: the physical stretching is just stretching, but classical yoga is historically a Hindu spiritual discipline, and elements that involve devotion to other gods, chanted mantras, or opening oneself to spiritual energies are not neutral for a believer (1 Corinthians 10:21 - 'ye cannot drink the cup of the Lord, and the cup of devils').

Many Christians therefore keep the stretching and drop the spirituality; others avoid it entirely for conscience's sake - and Romans 14 governs both: follow your conscience without judging the other (Romans 14:5,23). The test for any practice: does it belong to 'whatsoever things are pure' (Philippians 4:8), and can you do it 'to the glory of God' (1 Corinthians 10:31)?