Table 2. Internal load parameter for the total training sessions, p-values and effect size.

Parameter	Total	U15	U16	U18	P	ES$\left({\mathit{\eta }}_{\mathit{p}}^{\mathbf{2}}\right)$
HRmean [%]	82.14 ± 6.08	82.67 ± 5.81	82.72 ± 4.51	81.13 ± 7.70	0.717	0.016
HRz1 [s/min]	13.84 ± 8.74	13.47 ± 9.44	13.48 ± 7.52	14.58 ± 9.91	0.927	0.004
HRz2 [s/min]	14.32 ± 6.75	13.49 ± 4.67	14.69 ± 7.36	14.60 ± 7.85	0.878	0.006
HRz3 [s/min]	14.41 ± 7.24	15.50 ± 8.76	14.61 ± 5.47	13.33 ± 7.84	0.726	0.015
HRz4 [s/min]	16.78 ± 13.62	17.54 ± 12.96	17.21 ± 13.33	15.70 ± 15.20	0.927	0.004

HRmean in % compared to HRmax. HRz1: (<75% HRmax), HRz2: (75–84% HRmax), HRz3: (85–89% HRmax), HRz4: (≥90% HRmax). HR results are presented as mean ±SD.