An extraordinary number of studies have shown that creatine supplementation augments muscle size and strength gains when taken in conjunction with a resistance training program. Short-term use of creatine also has been shown to boost muscle strength.
In fact, a decade ago I published the first study that showed a one-week loading phase of creatine (25 g/day) enhanced bench press performance. At baseline subjects performed 5 sets of bench press with a weight they could perform 10 repetitions on the first set. When subjects did 5 sets with the same weight after one week of creatine supplementation, they were able to perform 2 more repetitions on the first set (12 vs 10), and over the 5 sets they performed a total of 8 more reps. In summary, acute creatine supplementation dramatically increases the ability to tolerate higher volumes of strength training.
A more recent study was published showing improved squat strength after short-term creatine supplementation. Maximal squat strength was measured before and after 6 days of creatine supplementation (20 grams/day) in healthy men. Maximal squat was 280 pounds at baseline and increased 14 pounds after just 6 days of supplementation. The research is clear that short-term creatine supplementation increases muscle strength, which over time translates into a better training stimulus for inducing gains in muscle.