One of the coaches who does kickboxing with us has a theory that the effect of a training session takes 20 days. So I only receive the physiological benefits of a training session 20 days after I do the work. Do you have any view on it?
I don't believe this is true, based largely on how training adaptations occur with regards to endurance, but also on how psychological factors influence performance on a day-to-day, or minute-by-minute basis, i.e. the difference in output between being psyched or not.
However, several factors are involved, mainly the condition of the athlete on Day 0 of the training program. The definition of "effect of training" factors as well. Does it mean full recovery? Or does it mean actual improved performance? Or something else? And how are the gains classified? Are the gains due to increased muscle volume or increased neurological efficiency (e.g. recruitment, or learned technique)? Different "systems" adapt at different rates. Training intensity affects recovery time, which suggests that intensity also affects functional and structural adaptations as well. The type and intensity of restoration and recovery practices speed not only recovery but super-compensation.
OK, some examples (of recovery and super-compensation):
The Norwegian Nordic ski team (national level) noted half-percent increase in VO2 Max per workout (!) during early-season blocks of intensive MVO2 training.
Platanov notes that recovery and adaptation times today are much faster than in the 1960s: six-day recovery cycle from 25-30% of the work done today, from which athletes routinely recover in three days.
Training to eccentric failure extends recovery time to up to 96 hours compared to training to positive failure, from which one might recover in 48-60 hours, compared to a brief anaerobic effort that might require as few as 3-8 hours to recover from.
A full-on aerobic effort, including intensive intervals, and done to exhaustion may take several days of recovery.
Zatsiorsky classifies training effects as:
Acute: changes occurring during the exercise
Immediate: caused by a single training session and manifested shortly thereafter
Cumulative: result of continuous training, measured over several sessions, or seasons
Delayed: changes manifested over a particular time interval following a training "routine", which I take to mean cycle: high stress for 3-4 weeks, reduced load, then the delayed effect of super-compensation
Partial: produced by reps or sets of a single exercise
Residual: effects accumulated during a a long-ish training period that remain after one stops training, and remain beyond the normal period of adaptation
Now that I have muddied the water I'll say that your man used a gross over-generalization, perhaps due to laziness, or ignorance, or misunderstanding. Perhaps he was referring to the purely physical characteristics of a single aspect of "performance" but since the mind/body connection is inseparable any conscious restricting of one's point of view is still wrong.