Walking during long runs is actually OK! and recommended.
Your shoes, MATTERS!
Strength Training is a MUST!
Sprints is a MUST!
Stretch & fix your stride
Walking during your long runs!
This technique is best applied when you are trying a new distance benchmark. Your brain and body gets accustomed to a set distance, their is a biological automation that settles in when you run say 5 miles everyday, all the time. The moment you try to add just 1 extra mile, their is what I would call a metabolic panic going on inside of you. It starts with the mental, and as doubt settles in, it affects your overall performance. Adding those walks is a literal way of telling your systems "see, no need to panic, we got this, lets set a new benchmark"
Another great analogy to this process is think back to the very first day you did something entirely different and unknown, that weird feeling of doubt you experienced, well it is the same principle when you are pushing your distance benchmarks.
Add a short walk or series of short walks AFTER completing your previous distance benchmarks. Once you get a nice feel of the new distance you simply reduce the number of walks until you simply run it through.
First dress appropriately for the weather. You do not want to overheat, and you also do not want to lose too much heat. The outside temperature will affect the quality of the air you are taking in, which can and often do affect performance. Your body releases its heat via sweat but certain areas are more prone to this thermal exchange, like your head, feet, and hands. Keep those protected during cold weather, and exposed during warm weather.
Your SHOES! No one likes blisters on their feet, it happens if your foot moves too much within its shoe, and chaffing of your toes. Go to a shoe store and get fitted, it will change your game!
Hydrate! Depending on your distance you may need to carry water with you. Always drink a lot before a run and always use the bathroom (if possible) before your run. But on long distance runs, you may want to invest in portable water bags for runners, holding a water bottle isn't the best solution.
Your body needs conditioning but you know what drives the your legs? your arms. Via what? Your hips. What prevents you from falling forward? Your back. How? because your abdominal and shoulders are stabilizing your trunk. How is your head so stable during your run? Your neck via what? Your chest.
If a single part of your chain is not able to perform, the cookie crumbles and injury will loom in the corner. Also you will not be able to run as fast nor as long, you will fatigue a lot faster.
Another benefit to an increase in muscle mass is an increase in glycogen storage, and glycogen is your main fuel of energy when in action. The bigger the storage the more fuel you hold in your tank.
Sprints is a Must!
As you train for your runs, incorporating sprints in your running routine will build power on your lower kinetic chain. Because you will only incorporate about 5% of your runs as sprints (1 sprint session a week) you wont build like a sprinter, so don't panic. However you will stimulate growth hormones which will help maintain your lean muscle mass but also help in your recovery in addition to the muscular endurance of your legs.
Stretch and fix your stride!
Running takes a toll on your body, but because you are incorporating weight lifting and sprints into your programs, your recovery is actually pretty good but not risk free. Always take the time to relax your muscles of your whole body, make the foam roller your mistress, enjoy it.
I always say that mother nature have designed us to run, but we messed it up because we are so conscious of how we "look" when we run, so we try to perform the "Baywatch stride". Truth is running stride has a strong science behind it, the energy generated NEEDS to be recycled and your body CAN do it easily by swigging your hips like a pendulum, and landing one foot in front of the other BELOW THE HIP ( unless your sprinting), striking the ground on your mid foot. A shoe store should be able to analyze your stride and recommend appropriate fixes.
Like i said earlier, too much thinking for something so natural, my recommended advice on stride fix...just let it go and run.