The government have offered advice for coaches and personal trainers on the phased return to sport and recreation:
If you are a personal trainer/coach you can now work with clients outdoors, providing you are alone and only meeting with 1 person from outside of your household, outdoors, and you are staying a minimum of 2 metres apart.
You can meet with different clients in a single day as long as it is only via one-to-one sessions and you are maintaining social distancing.
You should also enforce strong hygiene measures. This might be cleaning any equipment rigorously in line with wider guidance on hygiene, for example by using antibacterial spray and washing hands thoroughly before and after use.