Don't forget that laying down uses different muscles than when walking/standing so is it not reasonsable to assume that as the day goes by the body will become tired and those muscles will be affected. After my appendix was removed [14.02.1991 - what a Girl does to get flowers
] I was told not to drive for at least 6 weeks, due to sudden braking probably causing internal damage, also, the Insurance Company insisted on 6 weeks post surgery. By week 5 I knew that if I didn't get behind the wheel that day, I never would - so took myself off a t quiet time around the village driving carefully.
I was told not to lift anything heavier than a kettle but the day after discharge our heating packed up so I was carrying a blow heater from room to room ........
You have had a general anaesthetic probably and these are huge surgical interventions. The body can go into shock when interfered with. After my 3 wisdom teeth were removed under GA I was OK for 10 days then suddenly flopped. Became *extremely* tired, had to sleep for nearly 2 days ........ give yourselves some slack, get those feet up, cuppa to hand