Thank you both for your reply. I certainly understand your points of view from a musculoskeletal perspective in comparing the muscle activation and energy expenditures between cycling and running as well as the cardiovascular demands being different based on the workload between the two activities.
However, my challenge is whenever I run, I tend to get injured, typically in my gastroc/Achilles tendon complex or IT band. I can walk and hike for hours (I live in NH and typically have no problems hiking 6-8 hours in our mountains) with no adverse effects. However, I want to improve my CV fitness for Rainier. I imagine some walk/run interval could help but it may take months till I can run continuously for 60 minutes. I also have access to treadmill and stair climber for CV fitness which usually doesn’t present an injury risk when at the slower, non-running speeds which would be in my Z1 range.
Creativity will be key to improve CV fitness without increasing the risk of a lower extremity injury. Any other feedback??
Mike