Hello It is usually seen that whenever you first start exercising , as muscles are getting toned up and not used to that form of strain you get muscle pain in body parts . To avoid this its recommended that you increase your exercise activity gradually like first 5 days 20min then 30 min and so on. For your current situation 1.it is better to avoid doing during peak hour of heat that is between 11am till 5pm. 2. Drink lot of water . Dehydration can also cause muscle cramps. 3. You may apply volini gel to your knee joints 4. Shin bone pain , you better rule out vitamin D3 deficiency by blood test. 5. Don’t get stressed too much. Take care