Validity and Reliability
Validity and reliability are the most important parameters that sports scientists and practitioners should know about the tracking devices with GNSS receivers. Validity refers to how well a variable reflects what it intends to measure, while reliability refers to the consistency with itself (within-unit) and with other devices (between-unit) (Bassett, 2000). The validity of GNSS is vital due to an error that underestimates or overestimates the competition load directly influences a wrong design of training loads, which can lead to an increased risk of muscle injury (Cummins et al., 2013). For the validity assessments in team sports, most research presented its results as the standard error of measurement (SEM), the standard estimate of error (SEE), the percentage of differences (%diff), or the coefficient of variation (CV) from criterion measures. Otherwise, reliability is needed to allow the comparison between sessions and players, being the most common measures for reliability typical error of measurement (TEM), intraclass correlation coefficient (ICC) and CV (Hopkins, 2000). To interpret reliability results, previous recommendations shown the following rating: (a) good (>5%), (b) moderate (5–10%), or (c) poor (>10%) (Hopkins et al., 2009); but no recommendations have been realized for validity in sport science, so previous research adapted the recommendation for reliability on validity analysis for consistency and congruency (Scott et al., 2016).
Table 3.1 shows the validity and reliability analysis in the scientific literature of the devices that incorporate GNSS sensors for tracking purposes over 5 Hz in the Web of Science database on 15 November 2020. This criterion was employed as the noise calculated through TEM and CV in 1 Hz devices exceeds the signal smallest worthwhile changes and may not be capable of identifying the specific requirements in sports practice (Jennings et al., 2010a; Portas et al., 2010). A minimum of 10 Hz is necessary to achieve acceptable reliable and valid results through GNSS, but higher sampling frequency (15 and 18 Hz) have had no additional benefits. Literature suggests that >10 Hz GPS units are capable of registering time-motion demands as distance and average speed with adequate accuracy, intra- and inter-unit reliability to allow multiple comparisons of a single device and between devices. Data of peak speeds and instantaneous velocity distance covered and average speed during displacements are registered with good accuracy and reliability, but instantaneous speed should be treated with caution due to their lower precision and higher variability between devices.
Table 3.1 Validity and reliability results published in the scientific literature related to tracking devices with GNSS technology
Company Device SF Trials Assessment Criterion Variable Error Inter
Catapult MinimaxX
2.0
5 Hz Cricket running 600–8800 m
Validity Athletics track
Distance SEE = 1.7–
23.8 %
Good Sprints trials 20–
40 m Reliability Intra-unit Distance CV = 1.3–
30.0 % Good
Straight-line running
Validity Laveg laser Peak speed Avg speed
CV = 7.1–
33.2 % CV = 3.6–11.0
%
Mod po Go po Reliability Inter-unit Peak speed
Avg speed
CV = 9.5–
31.8 % CV = 6.3–12.4
%
Mod po M po Short high-
intensity specific movements and multidirectional running
Validity VICON motion analysis
Distance Avg speed Peak speed
4–6/6 NS 1–4/6 NS 6/6 NS
Good m M po Go Reliability Interunit Distance
Avg speed Peak speed
CV = 17.7–
22.8 % CV = 19.8–
33.4 % CV = 14.2–
31.5 %
Poor Po Po
MinimaxX team 2.5
5 Hz Sprint trials 10–
40 m Tight and gradual COD Team sport simulated circuit 3 AHL matches
Validity Measuring tape and goniometer
Distance SEE = 9.0–
30.9 %
Mod po
Reliability Intra-unit Distance CV = 6.6–
39.5 %
Mod po
Reliability Inter-unit Distance DBU = 9.5–11.6
Mod po Linear,
multidirectional and soccer- specific course
Validity Trundle wheel
Distance SEE = 1.5–
4.4 %
Good
Reliability Intra-unit Distance CV = 2.21–6.72
%
Good–
moderate Team sport
simulated circuit 50-m running
Validity Tape measure Timing lights Radar gun
Distance Avg speed Peak speed
NS NS NS Reliability Interunit Distance
Avg speed
TEM = 2.0–
112.0 % TEM = 7.5 %
Good–poor Moderate
Company Device SF Trials Assessment Criterion Variable Error Inter MinimaxX
v4.0
10 Hz Straight-line running
Validity Laveg laser Peak speed Avg speed
CV = 3.6–
11.3 % CV = 3.1–8.3
%
Good Go m
Reliability Inter-unit Peak speed Avg speed
CV = 1.9–
6.0 % CV = 2.0–5.3
%
Good m Go m 30 and 15 m
sprints
Validity Tape measure Distance SEM = 1.7–9.6%
Good m Reliability Intra-unit Distance CV <4 % Good Inter-unit Distance CV <1.3 % Good
Short high- intensity specific movements and multidirectional running
Validity VICON motion analysis
Distance Avg speed Peak speed
1–3/3 NS 0–3/3 NS 3/3 NS
Good Go po Go
70 m straight-line shuttle runs
Validity Radar Gun Distance HSR distance VHSR distance
CV = 1.9%
CV = 4.7%
CV = 10.5%
Good Go Po
MinimaxX S4
10 Hz 10 m sprint Validity Laser Peak speed SEE= 0.12–
0.32 m/s Good
m Reliability Inter-unit Peak Speed CV= 0.7–
9.1 %
Good m Team sport
simulated circuit (165 m)
Validity Tape measure Timing lights
Distance Peak speed
NS r= 0.89–
0.91
Good M po Reliability Inter-unit Distance
Peak speed
TEM= 1.3–
11.5 % TEM=
1.6 %
Good Go
Team sports specific circuit
Validity Tape measure Timing gates
Distance Avg speed
TEE= 3.0–
12.9 % TEE=
4.1–23.3
%
Good Go po
Reliability Inter-unit Distance
Avg speed CV= 2.5–
13.0%
CV= 3.3–
20.0 %
Good–poor Good–
poor MinimaxX
S5
10 Hz Team-sport simulation session
Reliability Inter-unit Distance Avg speed Peak speed
CV= 1.5–
3.1 % CV=
1.5–3.1
% CV=
0.3–1.9
%
Good Go Go
Company Device SF Trials Assessment Criterion Variable Error Inter
Exelio GPEXE PRO 18 Hz Team sports
specific circuit
Validity Tape measure Timing gates
Distance Avg speed
TEE= 1.6–
8.0 % TEE=
4.5–14.3
%
Good m Go po Reliability Inter-unit Distance
Avg speed
CV= 1.1–
5.1%
CV=
3.1–7.5
%
Good Go m
Advanced Sport Instruments
FieldWiz GPS
10 Hz 10-20-40 m straight-line runs, two change of direction runs and team-sport simulated circuit
Validity Trundle- wheel MinimaxX S4
Distance Peak speed
CV= 2.5 % CV=
2.1%
Good Go
Reliability Intra-unit Distance
Peak speed CV= 1.2 % CV=
2.3%
Good Go GPS Sport SPI-Pro 5 Hz Cricket running
600–8800 m Sprints trials 20–40 m
Validity Athletics
track Distance SEE = 0.4–
10.5% Good
m
Reliability Intra-unit Distance CV = 0.3–
9.3 %
Good m 10–30 m sprint Validity Tape measure
Timing gate
Distance
Avg speed CV= 4.81–
8.09 % CV=
5.68–
9.81 %
Good m M
Reliability Intra-unit Distance Speed
CV= 1.90–
2.30 % CV=
0.78–
20.6%
Good Go
70 m straight-line
shuttle runs Validity Radar Gun Distance HSR distance VHSR distance
CV = 2.8 % CV = 7.5
% CV = 23.2 %
Good M Po
SPI-Pro X 15 Hz Short high- intensity specific movements and multidirectional running
Validity VICON motion analysis
Distance Avg speed Peak speed
3–6/6 NS 3–6/6 NS 5–6/6 NS
Good Go po Go
Reliability Inter-unit Distance Avg speed Peak speed
CV= 6.2–
17.9 % CV=
7.5–16.3
% CV=
8.4–20.0
%
Mod po M po M po
Company Device SF Trials Assessment Criterion Variable Error Inter Team sport
simulated circuit (165 m)
Validity Tape measure Timing lights
Distance Peak speed
NS r= 0.64–
0.76
Good Po Reliability Inter-unit Distance
Peak speed
TEM= 1.9–
12.1 % TEM=
8.1 %
Good M
LIST shuttle and LIST curvilinear (13200 m)
Validity Surveyor
wheel Distance %diff=
2.16–
2.99 %
Good
Reliability Intra-unit Distance CV= 2.16–
2.44 %
Good Standardized
running routine Reliability Inter-unit Distance Accelerations Decelerations
CV= 2–6 % CV= 10–
43 % CV= 1–
56 %
Good m Po Go po 40m sprint test,
zig-zag test
Validity Distance
Avg speed
CV= 0.14–
3.73 % CV=
4.22–
9.52 %
Good Go m
Reliability Inter-unit Distance
Avg speed CV= 0.34–
3.81 % CV=
3.19–
6.95 %
Good Go m
EVO 10 Hz Team-sport
simulation session
Reliability Inter-unit Distance Avg speed Peak speed
CV= 0.2–
1.7 % CV=
0.2–1.7
% CV=
0.2–1.7
%
Good Go Go
Sport specific movements
Validity VICON Avg speed
Accelerations
SEE= 1.4–
4.5 % SEE=
1.5–6.1%
Good Go m JOHAN
Sports Johan GPS 10 Hz 200-m track-and- field
20-m shuttle run
Validity Tape measure Distance %diff= 1.06–
6.78
Good m
Reliability Inter-unit Distance CV= 1.31–
3.92 %
Good Intra-unit Distance ICC= 0.72–
0.83 Mod
po POLAR
Electro
POLAR Team Pro
10 Hz Linear and multidirectional movement task
Validity Tape measure Timing gates Laser
Distance Avg speed Peak speed
SEE= 1.0–
1.8 % SEE=
1.4–7.0
% SEE=
2.9–12.3
%
Good Go m Go po
Company Device SF Trials Assessment Criterion Variable Error Inter Reliability Inter-unit Distance
Avg speed Peak speed
CV= 1.0–
1.8 % CV=
1.1–4.9
% CV=
2.43–
12.86 % Good
Go Go po
RealTrack
Systems WIMU 5 Hz Circuit, 10-m and
30-m sprint test Validity Tape measure Distance %diff = 1.4–8.0
%
Good m Reliability Inter-unit Avg speed ICC = 0.98–
0.99
Good Intra-
unit
Distance Peak speed Avg speed
NS NS NS
Good Good Good WIMU PRO 10 Hz 3 Circuits with
linear, circular and zig-zag courses
Validity Timing gates Tape measure
Avg speed Distance
%diff = 0.69 to 6.05 %
%diff = -4.32 to 2.22 %
Good m Go
Reliability Inter-unit Avg speed Distance
Bias = 0.03 Bias = 0.25
Good Go Intra-unit Avg speed
Distance
ICC = 0.95 TEM = 1.47 %
Good Go Five courses: field
perimeter, halfway line, center circle, penalty area perimeter, semicircle penalty area and small-sided game
Validity Tape measure X coordinate Y coordinate
%diff = 2.69
%diff = 2.31
Good Go
Reliability Inter-unit Occupied area TEM = 1.98–
2.12 %
Good
Team-sport simulation circuit
Validity Timing-gates Avg speed SEE= 3.5
%
Good
STATSport Viper 10 Hz 5, 10, 15 and 20- m sprint
Validity Video analysis with Kinovea
Distance Avg speed
%diff= 3.5–
11.9 %
%diff= 5.9–8.2
%
Good M
5–30 m sprint Reliability Inter-unit Peak speed CV= 2.45
%
Good
40-m sprint Validity Timing gates Radar gun
Avg speed Peak speed
r= 0.97–
0.98 r= 0.99
Good Go
Company Device SF Trials Assessment Criterion Variable Error Inter
Reliability Avg speed
Peak speed
ICC= 0.94 ICC=
0.98–
0.99
Good Go
Apex 10 Hz 5–30 m sprint Reliability Inter-unit Peak speed CV= 1.85
% Good
Team-sport simulation session
Reliability Inter-unit Distance Avg speed Peak speed
CV= 0.3–
1.8 % CV=
0.3–1.8
% CV=
1.9–3.4
%
Good Go Go
Team-sport simulation circuit
Validity Timing-gates Avg speed SEE= 2.5
%
Good
Notes: SEE: Standard error of estimate; CV: Coefficient of variation; SEM: Standard error of measurement; TEM: Typical error of measurement; %diff: Percentage of difference; ICC: Intraclass correlation coefficient; DBU: Differences between units; NS: No significant difference to criterion.