I could exercise you could exercise she could exercise we could exercise you could exercise they could exercise
V-ing form
I could be exercising you could be exercising she could be exercising we could be exercising you could be exercising they could be exercising
Perfect
I could have exercised you could have exercised she could have exercised we could have exercised you could have exercised they could have exercised
V-ing perfect
I could have been exercising you could have been exercising she could have been exercising we could have been exercising you could have been exercising they could have been exercising
Negation
Simple form
I couldn't exercise you couldn't exercise she couldn't exercise we couldn't exercise you couldn't exercise they couldn't exercise
V-ing form
I couldn't be exercising you couldn't be exercising she couldn't be exercising we couldn't be exercising you couldn't be exercising they couldn't be exercising
Perfect
I couldn't have exercised you couldn't have exercised she couldn't have exercised we couldn't have exercised you couldn't have exercised they couldn't have exercised
V-ing perfect
I couldn't have been exercising you couldn't have been exercising she couldn't have been exercising we couldn't have been exercising you couldn't have been exercising they couldn't have been exercising
Interrogative form
Simple form
could I exercise? could you exercise? could she exercise? could we exercise? could you exercise? could they exercise?
V-ing form
could I be exercising? could you be exercising? could she be exercising? could we be exercising? could you be exercising? could they be exercising?
Perfect
could I have exercised? could you have exercised? could she have exercised? could we have exercised? could you have exercised? could they have exercised?
V-ing perfect
could I have been exercising? could you have been exercising? could she have been exercising? could we have been exercising? could you have been exercising? could they have been exercising?
Interro-negative form
Simple form
couldn't I exercise? couldn't you exercise? couldn't she exercise? couldn't we exercise? couldn't you exercise? couldn't they exercise?
V-ing form
couldn't I be exercising? couldn't you be exercising? couldn't she be exercising? couldn't we be exercising? couldn't you be exercising? couldn't they be exercising?
Perfect
couldn't I have exercised? couldn't you have exercised? couldn't she have exercised? couldn't we have exercised? couldn't you have exercised? couldn't they have exercised?
V-ing perfect
couldn't I have been exercising? couldn't you have been exercising? couldn't she have been exercising? couldn't we have been exercising? couldn't you have been exercising? couldn't they have been exercising?