Rules with sources. Explanations in plain language.

What science says

Polarized and pyramidal training outperform the threshold model (a lot of time at moderate-to-hard pace) in trained athletes. Between the two, the difference is small and depends on the person and the race. High-level endurance athletes spend 75% to 90% of their time at low intensity.

What science says

In 873 novice runners, increasing weekly distance by more than 30% over two weeks was associated with more distance-related injuries, but without statistical significance (risk 1.59; interval 0.96 to 2.66). Between 10% and 30% there was no clear difference. The 10% rule is a cautious reference, not a proven limit.

What science says

Meta-analysis: reducing volume progressively for about two weeks, while keeping intensity and frequency, improves performance. Reductions of 41% to 60% of volume were the most effective; 21% to 40% also helped.

What science says

Block periodization improves endurance performance, with few studies and almost all in cyclists. The 3:1 split (three loading weeks and one easy week) has no study to support it: it is a coaching convention.

What science says

Heavy strength training (from about 80% of 1RM) improves running economy and time-trial performance, with no effect on VO2max. The certainty of the evidence is moderate to low.

What science says

Adding endurance does not reduce maximal strength or hypertrophy; it reduces explosive strength, more so when both are in the same session. In the same session, doing strength first gives more leg strength gains. Interference grows with the frequency and duration of endurance work, and running interferes more than cycling.

What science says

Session perceived exertion (a 0 to 10 rating times the minutes) is a valid and reliable measure of internal load. Training guided by heart rate variability (HRV) improves things slightly and produces fewer non-responders, but the studies are small. The acute-to-chronic workload ratio (ACWR) has no evidence that it predicts injury.

What science says

Intervals of 30 s hard and 15 s easy, in sets, gave more VO2max and power than 4 × 5 min in trained cyclists, in studies lasting a few weeks. For sweet spot (88% to 94% of FTP) there is no direct basis proving it optimal.

What science says

Critical swim speed (CSS) is a valid field estimate, but it overestimates the lactate threshold by about 8%: it is better for following a trend. Short, intense training matched high-volume training in studies of a few weeks with young swimmers. Which drills work, almost no one has tested.

What science says

In recreational half-distance triathletes, pyramidal and polarized patterns were related to the result, in a small study. For the brick (bike followed by run) there are few studies, and the argument is specificity: running right after the bike changes the movement pattern.

What science says

There is a relationship between weekly volume and hypertrophy: 10 sets per muscle per week is a practical floor and 12 to 20 is the recommended range. Training each group 2 times a week or more is a reasonable pattern. Going to failure gives a trivial advantage for hypertrophy and none for strength. Resting more than 60 s between sets brings a small gain, and doing compound lifts first gives more strength in them.

What science says

Periodized training beats non-periodized training for maximal strength. Autoregulating by reps in reserve yields as much as fixed percentage-based loading or more, with few good studies. The deload (an easier week) is expert consensus, and the only trial with a deload week in the middle of nine found no benefit for hypertrophy.

What science says

Long static stretching (more than 60 s per muscle) before exercise reduces strength and power; up to 60 s within a dynamic warm-up has a trivial effect. Range of motion improves with weekly volume, around 10 minutes per week per muscle. Full range-of-motion strength training improves flexibility as much as stretching.

What science says

Guidelines for adults call for 150 to 300 minutes per week of moderate activity (or 75 to 150 of vigorous), strength exercise on 2 or 3 days and regular flexibility work.

What science says

The first session with a new exercise protects against damage and soreness in the following ones (the repeated bout effect), so strong soreness belongs to the first 1 or 2 weeks. Stretching before or after does not reduce soreness in a meaningful way. Foam rolling after training slightly reduces perceived soreness, and massage is the technique with the largest effect on delayed-onset soreness.