What a runner needs is not willpower, but detail.
Small differences break records and reduce injuries.

If you're running consistently but your records aren't improving and you're just getting injured again, it's time to check the details.
The author of "Detail Learning," Ku Hyeon-gyeong, is a trainer with a unique background, having previously worked as a private equity analyst.
After becoming a full-time trainer, he runs a fitness studio called 'Timber Modular', which teaches the principles of exercise.
In this book, he closely analyzes the body and movement to point out differences in breathing, posture, and landing that runners often miss.
He emphasizes that each runner must understand their own body and find a training method that suits them.

This book does not talk about willpower and mental strength.
Instead, it scientifically organizes the principles of breathing, posture, running dynamics, and injury prevention.
It is designed with abundant photos and illustrations so that anyone can immediately apply the correct running method.

For those who are easily anxious and tense, it is of great comfort to know that one can improve one's personality by changing one's physical and physiological conditions.
Breathing, and running which improves breathing ability, essentially improves both mental and physical constitution.

--- p.18

To exaggerate a bit, the only body tilt that health people know is the hip hinge.
(…) When people who have worked out a lot start running for the first time, they often see themselves running with their pelvis excessively bent.
Unlike weight lifting, running is an event that can last for 3 or 4 hours.
Is it possible to maintain a hip hinge and core lock throughout the entire exercise? If you experience lower back pain while running, check to see if you're using the wrong incline—that is, using a hip hinge—or creating excessive anterior pelvic tilt or lumbar extension.
--- p.36

A common cause of shoulder discomfort is the 11-figure arm swing.
When viewed from above the crown of the head, the human shoulder blades have a wide V-shaped angle that hugs the back inward.
This is called the scapular plane.
However, if you set your arms to 11, your shoulder blades will be brought back (posterior) and your back will become flat.
In particular, the rhomboid muscle, the muscle between the shoulder blades, becomes tense, and an uncomfortable resistance is felt around the neck, chest, and shoulders.
The discomfort is especially severe in people with short and tight pectoral muscles, front shoulder muscles, or upper trapezius muscles.
--- pp.45~46

In running, the core muscles stabilize by being flexible rather than stiff and stabilizing through abdominal pressure, as if you were squeezing your torso in the weight room.
Similar to core stabilization in sports that allow spinal movement, such as golf, tennis, and boxing.
Keep your front abs flat, focusing especially on your lower abs.
If you need more stability, hold it with a slightly bulging feeling to the side.
--- p.56

Before you blindly switch to a midfoot strike, I want you to first think about why you want to change your landing technique.
After suffering from a minor injury, I often feel like I want to change my landing technique when I easily conclude that it's my landing technique that's the problem.
However, there are many other variables involved in running that are related to injury.
Locally, these include stride length, cadence, speed, vertical oscillation, landing below the center of gravity, and even running rhythm, while larger-scale factors include training frequency and intensity, as well as external factors such as the runner's body weight, strength level, and flexibility.
--- pp.73~74

From resting to zone 2, the body relies primarily on fat for energy.
Fat is an efficient source of energy, but it requires oxygen to be metabolized.
Zone 2 can be seen as the area where you exert your maximum effort without going over the energy source crossover point (VT1, LT1) where you transition from an aerobic to an anaerobic state.
By exercising just below threshold like this, your body becomes more effective at using fat as a source of energy, increases the number and function of mitochondria in your muscle fibers (especially slow-twitch fibers), and improves their ability to process lactate.
--- p.124~125

Beginners who do not have a good sense of what their own pace is, whether fast, normal, or slow, will have uneven paces if they set their goals based on distance, and they are especially prone to overpacing in the latter half of the race in the hopes of covering the distance quickly.
If you are a beginner, I recommend using time rather than distance as your standard.
This will increase the likelihood of setting realistic goals from the outset, increasing your achievement rate and making your pace more relaxed and consistent.
--- p.142~143

Most good runners have short ground contact times, high cadences, high take-off power, and increased stride length.
Beginners should be wary of the chicken-and-egg problem.
This means that you should not misunderstand and think, 'People who run well have long strides, so if I want to run well, I have to run comfortably.'
A wide stride is the result of the effort a runner puts into building strength, rhythm, and speed as they move past their beginner stage.
If you follow along rashly, you might get hurt.
--- p.152

A common postural problem that occurs in the pelvis when landing from running is the pelvis falling to one side.
In this case, the energy of the lower body leaks out to the side, and the rigidity of the lower body required for landing cannot be created, but the bigger problem is that the muscles cannot elastically absorb the shock of hitting the ground with the body weight, so the stimulus is transmitted to the joints.
In particular, the muscles on the outside of the leg become shortened, making them vulnerable to injuries such as iliotibial band syndrome, which causes pain on the outside of the knee when going down stairs.
The chain of compensatory forces can cause the ankle to roll inward, which can cause discomfort around the ankle.
--- p.187

This breathing technique, called cyclic sigh or physiological sigh, is effective in improving mood and reducing stress, and is also useful during exercise.
It is one of the most effective breathing techniques for activating the parasympathetic nervous system of the body.
When you feel out of breath or have pain in your side during exercise, it immediately lowers your heart rate, stabilizes your breathing, and relieves pain.
(…) The breathing method is to take two deep breaths through the nose and then exhale once long through the mouth. Take one deep breath, then take a short, strong breath for the second time and then exhale all the air through the mouth.

--- pp.222~223