A study compared the effects of a traditional warm-up with two post-activation potentiations (PAP) warm-up strategies on the repeated sprint ability (RSA) of soccer players from national (NL) and regional (RL) competitive levels. Sixteen young players were recruited to complete a traditional warm-up, a PAP warm-up incorporating squats with a load (~60% 1RM) that allowed a high speed (1 m/s) of movement and a high number of repetitions (PAP-1), and a PAP warm-up with a load (~90% 1RM) that allowed a moderate speed (0.5 m/s) of movement and a reduced number of repetitions (PAP-0.5).

The ability to sustain repeated explosive actions during a match is a key issue in soccer. Improvement of these explosive performances (e.g., sprinting speed) have been chronically reported after muscular strength training programs, although acute improvements may also be obtained under specific conditions. Apart from reducing the injury risk, a warm-up can also acutely improve explosive performance.

However, more traditional warmup strategies usually encompass low-intensity endurance exercise (e.g., running), flexibility and sport-specific drills, and may not optimize explosive strength. In soccer, warm-up strategies should aim to increase muscle temperature and neural activation, while minimizing fatigue. 

The study hypothesis was that the two PAP warm-up strategies would induce greater effects on the RSA of soccer players compared to the traditional warm-up, with greater effects in national-level athletes. The main results showed that neither PAP-1.0 nor PAP-0.5 resulted in substantial improvements in RSA performance when data of both NL and RL athletes were combined.

However, the assessment of the two groups separately revealed meaningful improvements in both RSAb and RSAm for the NL athletes following the PAP-0.5 protocol. A potential limitation of the present study deals with its ecological validity. To induce PAP effects, soccer players completed explosive squats at maximal-voluntary velocity. Aside from logistical difficulties to implement them before games, safety considerations should be addressed by qualified personnel, which may be difficult especially in amateur clubs.

Future studies should aim to establish ecologically valid PAP strategies, best suited to the warm-up conditions encountered before competitive soccer matches, such as plyometric drills or similar body-weight drills, emphasizing soccer-specific actions.

In conclusion, neither PAP-1.0 nor PAP-0.5 resulted in substantial improvements in RSA performance when the data of both NL and RL athletes were combined. However, the assessment of the two groups separately revealed meaningful improvements in both RSAb and RSAm for the NL athletes following the PAP-0.5 protocol. Therefore, adding a heavy strength-based conditioning exercise during the warm-up may induce a small improvement in RSA in soccer players, with up to large improvements in those from a greater competitive level.