The appropriate training time distribution within zones 2 and 3 for easy runs can vary depending on individual fitness levels, training goals, and personal preferences. However, in general, many athletes and coaches recommend spending more time in zone 2 for easy runs as it allows for better aerobic development, endurance building, and recovery.
While spending some time in zone 3 during easy runs can be beneficial, it's generally recommended to prioritize zone 2 training to build a solid aerobic foundation. A 50-50% distribution may shift the focus towards zone 3 too much, potentially hindering the recovery and aerobic development that zone 2 training provides.
It's important to note that overall training intensity distribution should also consider harder workouts, like interval sessions or tempo runs, as incorporating varying intensity levels is crucial for a well-rounded training plan. It's always a good idea to consult a knowledgeable coach or trainer who can provide personalized guidance based on your specific goals and fitness level.