THE RESEARCH PLAYBOOK
TABLE 1
Table 1. Mean rotational resistance, soil moisture, thatch depth, and infill depth data for both areas within each of the four fields studied. Means followed by different letters within the same row are significantly different according to Fisher’ s protected least significant difference( LSD) test at = 0.05.
Hard Area Average Soft Area Average
FIELD |
Rotational Resistance( Nm) |
Soil Moisture(%) |
Thatch Depth( mm) |
Infill Depth( mm) |
Rotational Resistance( Nm) |
Soil Moisture(%) |
Thatch Depth( mm) |
Infill Depth( mm) |
Low-usage natural turfgrass field
High-usage natural turfgrass field
Low-usage synthetic turf field
High-usage synthetic turf field
32.9 A |
40.9 A |
27.4 A |
N / A |
30.4 A |
39.4 A |
40.9 A |
N / A |
35.1 B |
35.8 B |
11.1 B |
N / A |
33.2 B |
42.4 B |
25.1 B |
N / A |
25.6 C |
N / A |
N / A |
39.7 A |
25.8 C |
N / A |
N / A |
42.3 A |
22.3 D |
N / A |
N / A |
31.3 B |
24.2 D |
N / A |
N / A |
33.5 B |
the ground reaction forces, which in turn raise lower limb impact loads( Leatham, 2004; Jiang et al., 2024). If athletes ran at different speeds across field types, it could have confounded interpretation of the ankle IMU data by introducing speed-related variation in impact load. However, since no significant speed differences were found across field types, usage levels, or hardness zones, we can more confidently attribute the observed differences in ankle IMU data to the playing surface.
ANKLE IMU DATA Ankle IMUs were utilized to record a metric called average intensity, which is defined as the mean impact intensity derived from every impact propagated into both limbs( IMeasureU, 2022). This metric is recorded in units of gravitational force( g). The devices were securely attached to each athlete’ s ankle and recorded data as the athletes performed drills on all four fields studied. After running statistical tests that accounted for individual differences between athletes, significant differences were found based on field type, usage levels, and hardness zones.
Across all three drills, field type had a noticeable impact( p < 0.0001) where athletes showed higher average intensity on synthetic turf fields compared to natural turfgrass. For the drop jump drill, the average intensity was 19.73 g [ standard error( SE) ± 1.88 ] on natural turfgrass and 22.73 g( SE ± 1.82) on synthetic turf, placing the synthetic turf value within the IMU Step‘ high intensity’ foot strike range of 21.5 – 26.7 g( Wong and Finch, 2018). A similar trend was seen in the t-drill, with average intensities of 15.84 g( SE ± 1.20) on natural turfgrass and 18.07 g( SE ± 1.16) on synthetic turf. For the modified acceleration-deceleration drill, average intensity was 17.72 g( SE ± 1.15) on natural turfgrass and 21.35 g( SE ± 1.10) on synthetic turf.
Field usage also made a difference in the t-drill( p < 0.0001), where the average intensity on high-usage fields was 18.14 g( SE ± 1.24), compared to 16.49 g( SE ± 1.24) on low-usage fields. Hardness played a role as well, especially in the t-drill( p = 0.0073) and the modified acceleration-deceleration drill( p < 0.0001). In the t-drill, hard areas resulted in an average intensity of 17.43 g( SE ± 1.22), slightly higher than the 17.05 g( SE ± 1.22) on soft areas. For the modified acceleration-deceleration drill, intensity averaged 20.38 g( SE ± 4.28) on hard areas and 18.85 g( SE ± 3.81) on soft areas. sportsfieldmanagementonline. com August 2025 | SportsField Management
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