Yur father. He is exerting for 3 hours more than you. Also, he is conditioning his cardio-vascular system more.
I biked for 20 years, avidly and fast, uphill and down. I was fat and smoked the whole time. In my adulthood, I have taken up walking. I've lost 40lb in 4 months. There is NO comparison!
I biked for 20 years, avidly and fast, uphill and down. I was fat and smoked the whole time. In my adulthood, I have taken up walking. I've lost 40lb in 4 months. There is NO comparison!