Depends very much on how close people come to each other and how often,
what they touch,
how many people in the vicinity
Also whether the type of activity risks breaking the 2m rule
e.g. the law here (Germany) has been tightened to try to exclude this:
"a minimum distance of 1.5 meters must be maintained.
Public behavior that is likely to jeopardize the distance requirement of sentence 2, such as partying, barbecuing or picnicking,
is prohibited regardless of the number of people"
The lockdown in the UK seems lighter touch than in other countries
and all European lockdowns are much lighter than in Wuhan
We will see from the UK figures over the next few weeks if this matters
Rather too late for studies atm if it does