Do I'm in my 60's and started riding on my $50 Schwinn hybrid 6 weeks ago. Worked up to 23 miles a week, which includes riding 5 or 6 times a week. Every day now, I feel wiped out and so tired. Does this go away? The heaviness in my legs when I first start out, does that go away? I'm doing 90% trail riding, lots of up and down with little hills. Thank you.