Maturity status influences perceived training load and neuromuscular performance during an academy soccer season

Figures & data

Table 1. Descriptive statistics of anthropometric and neuromuscular characteristics (mean ± SD) according to age category at the start of the season, and mean ± SD weekly differential-RPE (AU) values over the season.

	U13 (n = 12)	U14 (n = 9)	U15 (n = 9)	U16 (n = 7)
Age (y)	12.6 ± 0.3	13.5 ± 0.6	14.8 ± 0.1	15.7 ± 0.2
Stature (m)	160.0 ± 7	166.0 ± 7	177.0 ± 5	179.0 ± 9
Body mass (kg)	49.9 ± 8	56.5 ± 9	63.4 ± 4	65.2 ± 9
Status (PAH%)	88.7 ± 2	92.2 ± 2.7	97.0 ± 1	98.6 ± 1
Tempo (cm/year)	12.1 ± 6	8.7 ± 7	7.4 ± 10	7.1 ± 4
sRPE	52.1 ± 15	50.8 ± 14	45.9 ± 12	43.2 ± 12
RPE-B	48.0 ± 13	50.5 ± 14	48.0 ± 12	45.5 ± 12
RPE-L	51.3 ± 15	52.8 ± 15	46.2 ± 10	46.4 ± 12
RPE-T	45.2 ± 13	49.3 ± 15	43.6 ± 11	41.2 ± 11
CMJ	22.0 ± 3	29.7 ± 4	33.1 ± 6	33.9 ± 4
RSI	0.6 ± 0.2	0.7 ± 0.2	0.56 ± 0.2	0.6 ± 0.1
ABS	15.4 ± 6	18.6 ± 8	18.9 ± 5	19.7 ± 5
REL	26.2 ± 12	25.6 ± 12	25.4 ± 7	24.9 ± 6

PAH%, percentage of predicted adult height; sRPE, sessional rating of perceived exertion; RPE-B, RPE breathlessness; RPE-L, RPE-leg exertion; RPE-T, RPE-technical exertion; CMJ, countermovement jump; RSI, reactive strength index; ABS, absolute stiffness; REL, relative stiffness

Figure 1. Box (25^th to 75th percentile) and whisker (minimum and maximum) ratings of each differential-RPE across chronological age-groups for the full season aligned to the verbal anchors of the Borg CR-100 centi-MAX scale.

Table 2. Slope, mean difference (95% confidence interval), effect size (d) and non-clinical practical inferences (probabilities) for 5% and 10% increments in PAH.

Variable	±PAH%	df	t	P	Difference (95% CI)	d	Non-clinical inference
sRPE	cm/year	36	5.61	0.115	0.3 (−0.1 to 0.9)	0.02	Most likely trivial (0/100/0)
	5%	65	−3.33	0.002*	−6.9 (−11.1 to −2.7)	0.75	Likely trivial (0/71/29)
	10%	51	−3.33	0.002*	−13.9 (−22.3 to −5.5)	1.01	More mature likely lower (0/7/93)
RPE-B	cm/year	15	1.41	0.182	0.4 (−0.2 to 1.0)	0.03	Most likely trivial (0/100/0)
	5%	30	0.81	0.423	1.3 (−1.9 to 4.5)	0.24	Most likely trivial (0/100/0)
	10%	30	0.81	0.423	2.6 (−3.9 to 9.1)	0.42	Very likely trivial (5/95/0)
RPE-L	cm/year	18	0.52	0.606	0.2 (−0.5 to 0.8)	0.01	Most likely trivial (0/100/0)
	5%	23	−0.31	0.755	−0.6 (−4.5 to 3.3)	0.10	Most likely trivial (0/100/0)
	10%	23	−0.31	0.755	−1.2 (−9.1 to 6.7)	0.13	Very likely trivial (1/95/4)
RPE-T	cm/year	64	1.31	0.192	0.3 (−0.2 to 0.8)	0.03	Most likely trivial (0/100/0)
	5%	8	−0.63	0.529	−1.1 (−4.6 to 2.3)	0.16	Most likely trivial (0/100/0)
	10%	8	−0.65	0.532	−2.1 (−9.4 to 5.2)	0.29	Very likely trivial (0/95/5)
CMJ	cm/year	19	−0.96	0.348	−0.1 (−0.2 to 0.1)	0.03	Most likely trivial (0/100/0)
	5%	58	4.89	0.001*	4.3 (2.5 to 6.1)	1.72	More mature most likely higher (99/1/0)
	10%	58	4.89	0.001*	8.6 (5.1 to 12.1)	3.03	More mature most likely higher (100/0/0)
RSI	cm/year	60	0.42	0.674	0.1 (−0.1 to 0.1)	0.02	Most likely trivial (0/100/0)
	5%	75	2.1	0.038*	0.1 (0.1 to 0.2)	1.44	More mature likely higher (90/10/0)
	10%	65	1.98	0.052	0.2 (−0.1 to 0.4)	3.06	More mature very likely higher (95/4/1)
ABS	cm/year	9	−1.16	0.463	−0.3 (−4.3 to 3.7)	0.27	Most likely trivial (0/100/0)
	5%	67	2.10	0.043*	2.8 (0.9 to 5.5)	0.58	More mature likely higher (90/10/0)
	10%	84	2.10	0.043*	5.6 (0.2 to 11.1)	1.53	More mature very likely higher ((95/4/1)
REL	cm/year	29	−0.67	0.507	−0.17 (−0.7 to 0.4)	0.02	Most likely trivial (0/100/0)
	5%	57	1.1	0.285	2.7 (−2.3 to 7.7)	0.57	Unclear (65/30/5)
	10%	48	1.1	0.255	6.1 (−4.5 to 16.8)	1.73	Unclear (80/14/6)

Abbreviations: RPE, rating of perceived exertion; sRPE, sessional-RPE; RPE-B, breathlessness; RPE-L, leg muscle exertion; RPE-T, Technical/cognitive exertion; CMJ, countermovement jump; RSI, reactive strength index; ABS, absolute stiffness; REL, relative stiffness; cm/year, maturation tempo; PAH%, percentage of adult height; df, degrees of freedom; t, t-statistic; P, p-value; * denotes significant p-value <0.05

Figure 2. Forecasted accumulated training load differences in sRPE over a typical season for players of varied maturation.