Table 3 Quantitative performance indices of men's professional tennis matches played on hard and clay courts.
| Hard court | Clay court | |
|---|---|---|
| Mean (SD) | Mean (SD) | |
| First serve velocity (kph) | 178 (9) | 172 (14) |
| (n = 445) | (n = 375) | |
| Second serve velocity (kph) | 135 (10) | 134 (12) |
| (n = 199) | (n = 147) | |
| First serve accuracy (%) | 56 (24) | 55 (24) |
| Points won on first serve (%) | 72 (33) | 76 (25) |
| Points won on second serve (%) | 63 (34) | 61 (35) |
| Unforced errors (%) | 24 (13) | 24 (17) |
Of the two players contesting each match, values (mean (SD)) represent those of only the player participating in the investigation (n = 6). Values in parentheses (n) represent the number of data from which mean and SD are derived.