Can humans survive 2 times gravity?

Yes, humans can survive and adapt to 2g (double Earth's gravity), though it would be extremely challenging. Short-term exposure causes discomfort, fatigue, and difficulty breathing and moving. Long-term adaptation might be possible with training, but would cause cardiovascular strain (heart working twice as hard), bone and muscle stress, circulation problems, and reduced mobility. People with heart conditions or elderly individuals would struggle severely. Athletic activities would be nearly impossible without superhuman conditioning.