A study protocol for the development and internal validation of a multivariable prognostic model to determine lower extremity muscle injury risk in elite football (soccer) players, with further exploration of prognostic factors

Hughes, Tom; Riley, Richard; Sergeant, Jamie C.; Callaghan, Michael J.

doi:10.1186/s41512-019-0063-8

Table 1 List of candidate prognostic factors, methods and units of measurement, frequency of complete and incomplete observations and proportion of missing observations

From: A study protocol for the development and internal validation of a multivariable prognostic model to determine lower extremity muscle injury risk in elite football (soccer) players, with further exploration of prognostic factors

Type of prognostic factor	Candidate prognostic factor	Measurement method	Measurement unit	Data type	Complete obs	Missing obs	Percent missing (%)
Anthropometric	Age	Birthdate	Years	Cont.	317	0	0
	Height	Standing height	cm	Cont.	299	18	5.68
	Weight	Digital scales	kg	Cont.	299	18	5.68
	BMI	Height/weight	kg/m²	Cont.	294	23	7.26
	Body fat	Skin callipers	%	Cont.	75	242	76.34
Medical history	Frequency of previous IMIs within 3 years prior to PHE	Medical records	Freq.	Dis./cont.	317	0	0
	Most recent previous IMI within 3 years prior to PHE	Medical records	Never, < 6 months, 6–12 months, > 12 months	Cat.	317	0	0
	Frequency of previous foot or ankle injuries within 3 years prior to PHE	Medical records	Freq.	Dis./cont.	317	0	0
	Most recent previous foot or ankle injury within 3 years prior to PHE	Medical records	Never, < 6 months, 6–12 months, > 12 months	Cat.	317	0	0
	Frequency of previous hip or groin injuries within 3 years prior to PHE	Medical records	Freq.	Dis./cont.	317	0	0
	Most recent previous hip or groin injury within 3 years prior to PHE	Medical records	Never, < 6 months, 6–12 months, > 12 months	Cat.	317	0	0
	Frequency of previous knee injuries within 3 years prior to PHE	Medical records	Freq.	Dis./cont.	317	0	0
	Most recent previous knee injury within 3 years prior to PHE	Medical records	Never, < 6 months, 6–12 months, > 12 months	Cat.	317	0	0
	Frequency of previous shoulder injuries within 3 years prior to PHE	Medical records	Freq.	Dis./cont.	317	0	0
	Most recent previous shoulder injury within 3 years prior to PHE	Medical records	Never, < 6 months, 6–12 months, > 12 months	Cat.	317	0	0
	Frequency of previous lumbar spine injuries within 3 years prior to PHE	Medical records	Freq.	Dis./cont.	317	0	0
	Most recent previous lumbar spine injury within 3 years prior to PHE	Medical records	Never, < 6 months, 6–12 months, > 12 months	Cat.	317	0	0
	Frequency of previous iliopsoas IMIs within 3 years prior to PHE	Medical records	Freq.	Dis./cont.	317	0	0
	Most recent previous iliopsoas IMI within 3 years prior to PHE	Medical records	Never, < 6 months, 6–12 months, > 12 months	Cat.	317	0	0
	Frequency of previous adductor IMIs within 3 years prior to PHE	Medical records	Freq.	Dis./cont.	317	0	0
	Most recent previous adductor IMI within 3 years prior to PHE	Medical records	Never, < 6 months, 6–12 months, > 12 months	Cat.	317	0	0
	Frequency of previous hamstring IMIs within 3 years prior to PHE	Medical records	Freq.	Dis./cont.	317	0	0
	Most recent previous hamstring IMI within 3 years prior to PHE	Medical records	Never, < 6 months, 6–12 months, > 12 months	Cat.	317	0	0
	Frequency of previous quadriceps IMIs within 3 years prior to PHE	Medical records	Freq.	Dis./cont.	317	0	0
	Most recent previous quadriceps IMI within 3 years prior to PHE	Medical records	Never, < 6 months, 6–12 months, > 12 months	Cat.	317	0	0
	Frequency of previous calf IMIs within 3 years prior to PHE	Medical records	Freq.	Dis./cont.	317	0	0
	Most recent previous calf IMI within 3 years prior to PHE	Medical records	Never, < 6 months, 6–12 months, > 12 months	Cat.	317	0	0
Musculoskeletal	PROM R hip joint internal rotation	Digital inclinometer	Degrees	Cont.	297	20	6.31
	PROM L hip joint internal rotation	Digital inclinometer	Degrees	Cont.	297	20	6.31
	PROM R hip joint external rotation	Digital inclinometer	Degrees	Cont.	297	20	6.31
	PROM L hip joint external rotation	Digital inclinometer	Degrees	Cont.	297	20	6.31
	R hip flexor muscle length	Digital inclinometer—Thomas test	Degrees	Cont.	294	23	7.26
	L hip flexor muscle length	Digital inclinometer—Thomas test	Degrees	Cont.	294	23	7.26
	R hamstring muscle length /neural mobility	Digital inclinometer—SLR	Degrees	Cont.	297	20	6.31
	L hamstring muscle length /neural mobility	Digital inclinometer—SLR	Degrees	Cont.	297	20	6.31
	R quadriceps muscle length	Goniometer—Ely’s test	Degrees	Cont.	297	20	6.31
	L quadriceps muscle length	Goniometer—Ely’s test	Degrees	Cont.	297	20	6.31
	R calf muscle length	Digital inclinometer—WBL	Degrees	Cont.	297	20	6.31
	L calf muscle length	Digital inclinometer—WBL	Degrees	Cont.	297	20	6.31
	Toe touch in standing	Fingertip-floor distance	cm	Cont.	250	67	21.14
	Sacroiliac joint kinematic function	Gillet’s test	Subjective kinematic function	Cat.	250	67	21.14
Functional movement/balance	Y Balance Test—R anterior translation	Y Balance Test	cm	Cont.	179	138	43.53
	Y Balance Test—L anterior translation	Y Balance Test	cm	Cont.	179	138	43.53
	Y Balance Test—R posteromedial translation	Y Balance Test	cm	Cont.	179	138	43.53
	Y Balance Test—L posteromedial translation	Y Balance Test	cm	Cont.	179	138	43.53
	Y Balance Test—R posterolateral translation	Y Balance Test	cm	Cont.	179	138	43.53
	Y Balance Test—L posterolateral translation	Y Balance Test	cm	Cont.	179	138	43.53
	R relative tibial angles	SLS measured with IMU	Degrees	Cont.	*	*	*
	L relative tibial angles	SLS measured with IMU	Degrees	Cont.	*	*	*
Strength/power	R upper body peak power	Horizontal press	W/kg^−0.67	Cont.	178	139	43.85
	L upper body peak power	Horizontal press	W/kg^−0.67	Cont.	178	139	43.85
	R maximal loaded leg extension power	Double leg press	W/kg^−0.67	Cont.	276	41	12.93
	L maximal loaded leg extension power	Double leg press	W/kg^−0.67	Cont.	276	41	12.93
	R maximal loaded leg extension velocity	Double leg press	m s⁻¹	Cont.	276	41	12.93
	L maximal loaded leg extension velocity	Double leg press	m s⁻¹	Cont.	276	41	12.93
	R maximal loaded leg extension force	Double leg press	N/kg^−0.67	Cont.	276	41	12.93
	L maximal loaded leg extension force	Double leg press	N/kg^−0.67	Cont.	276	41	12.93
	CMJ height	CMJ	cm	Cont.	275	42	13.25
	CMJ force per kilogram of body mass	CMJ	N/kg	Cont.	275	42	13.25
	CMJ peak power	CMJ	W	Cont.	275	42	13.25

Freq. frequency, obs observations, PHE periodic health examination, IMI indirect muscle injury, WBL weight bearing lunge, CMJ countermovement jump, PROM passive range of movement, SLR straight leg raise, SLS single leg squat, IMU inertial measurement units, BMI body mass index, kg/m² kilograms/body height (metres) squared, W watts (note: W/kg^−0.67 has a scaling factor to normalise power to body mass), N newtons (note: N/kg^−0.67 has a scaling factor to normalise force to body mass), cm centimetres, kg kilograms, Cont. continuous, dis./cont. discrete treated as continuous, cat categorical, R right, L left, m s^-1 metres/second, “–” not applicable/not available, “*” missing data analysis not completed—test evaluated through a reliability/agreement study published as a related part of this project and excluded from further analysis based on the results

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