REF-1628 · Rønnestad, Nymark & Raastad, 2011 · Journal of Strength and Conditioning Research, Vol. · Paper · PubMed
In professional soccer players, one strength session a week kept the leg strength and 40-m sprint gained in a 10-week, twice-weekly preseason through the first 12 weeks of the season, while with one session every second week both fell (7 players per group); jump height did not change significantly in either group
Main caveat: 7 players per group: the result shows a direction, not a reliable size, and the abstract gives no magnitudes.
Rønnestad, Nymark and Raastad asked how often professional soccer players must lift in season to keep what they gained in the preseason. All players followed one strength programme twice a week for a 10-week preparatory period, which raised strength, 40-m sprint performance and jump height.
In season, one group did one maintenance session a week (2 + 1, n = 7) and the other one session every second week (2 + 0.5, n = 7); exercises, sets, RM loads and soccer sessions were alike, so only the frequency differed.
Over the first 12 weeks of the season the weekly group kept its strength and sprint gains, while the fortnightly group lost leg strength and sprint performance. Jump height did not change significantly in either group. The authors conclude that, over a 12-week period, one session a week may be enough to hold the strength and sprint gained in the preseason.
Participants
n = 14 professional soccer players (7 + 7, our arithmetic), 7 per group.
Men by the PubMed indexing (MeSH Male); young adults by the PubMed indexing; Norway by the PubMed indexing.
Age, playing position, club, league and training history: not in the abstract.
Protocol
Preparatory period, 10 weeks: the same strength programme twice a week for all players.
In season, first 12 weeks: group 2 + 1 did one strength maintenance session a week; group 2 + 0.5 did one every second week.
Held alike between the groups: exercises, sets, repetition-maximum loads and soccer sessions.
Outcomes: strength (leg strength, per the conclusion), jump height and 40-m sprint.
Not in the abstract: how players were allocated, the exercises, sets and loads, the strength test used, match and training load in season, and between-group statistics.
Key Results
| Outcome | Preseason, 10 weeks at 2 sessions a week (all players) | In season, 12 weeks: 1 session a week (n = 7) | In season, 12 weeks: 1 session every second week (n = 7) |
|---|---|---|---|
| Leg strength | increased (p < 0.05) | gain kept | fell (p < 0.05) |
| 40-m sprint | improved (p < 0.05) | gain kept | worse (p < 0.05) |
| Jump height | increased (p < 0.05) | no significant change | no significant change |
Not in the abstract: any magnitude (kg, %, s or cm), and whether the two groups differed from each other statistically.
Practical Application
Keep one strength session every week in season; every second week was not enough. After 10 weeks of twice-weekly preseason lifting, one session a week held leg strength and 40-m sprint over the first 12 weeks of the season, and one every second week lost both, at the same exercises, sets and RM loads.
Cut frequency to one a week, not to one a fortnight. The authors report that only the in-season frequency differed (exercises, sets, RM loads and soccer sessions similar), but the abstract gives within-group changes only, with no test between the groups, 7 per group and no description of allocation, so this is a direction, not a proven cause.
Inference, not tested here: do not use jump height alone to check that strength is being kept. Jump did not change in either group, while the fortnightly group lost strength and sprint.
Inference, not tested here: the same weekly floor for endurance athletes. Well-trained cyclists kept their strength gains on one session a week in season (REF-800), and in untrained women one session a week held strength while one every second week gave some back (REF-1136); this soccer trial points the same way. The base's in-season defaults are in SYNTH-43 and SYNTH-44.
Not settled by this trial: it ran for 12 weeks; how long one session a week holds beyond that, and whether a lighter load or fewer sets would also hold, were not tested. An occasional missed week was not tested either: the fortnightly pattern ran for the whole 12 weeks.
Limitations
7 players per group: the result shows a direction, not a reliable size, and the abstract gives no magnitudes.
The abstract reports changes within each group; a test between the groups is not in it. Allocation is not described (PubMed indexes the study as randomised).
No group stopped lifting, so how fortnightly sessions compare with none is unknown.
Only the first 12 weeks of the season; matches, other training and injuries in that time are not in the abstract.
Professional soccer players only (men, by the PubMed indexing); transfer to women, amateurs and endurance athletes is inference.
Written from the abstract and the PubMed record; full text not read.
How this entry was checked and changed
Why this level
a parallel trial with 7 per arm (under 10 per arm is B, rubric); the abstract does not describe the allocation, gives no magnitudes and reports within-group changes only
Content correction 2026-11-06
2026-11-06: added from the abstract and the PubMed record; level B (parallel trial, 7 per arm).