The individuality of training is too often neglected, especially with so many runners running in groups and as part of running clubs. Both research and empirical evidence shows that there is a large inter-individual response to training, both in the magnitude of response and in the time frame for developing and retaining training effects.
What may work for one runner may not work for another. Not all runners who are capable of the same performance have the same work capacity. Some runners may respond better to high volume and low intensity while some may respond better to low volume and high intensity. Some need more recovery days between hard workouts than others. It’s important to know your training needs or, if you’re a coach or trainer, the needs of those you coach, and to individualize the training, even when in a group setting.
Training should also be individualized based on workout stress in addition to the strengths and weaknesses of each runner. For example, since the time under stress is what matters, not the actual distance, base workouts on time. If Jack and Jill do a 5-mile tempo run at lactate threshold pace to fetch a pail of water, and Jack runs 7:30 per mile pace and Jill runs 6:30 per mile pace, Jack has a more difficult workout because it’s going to take him 5 minutes longer to run 5 miles at threshold pace (and Jill will get all the water).