In this study, HRRec was determined as the difference between the Yo-Yo intermittent tests’ peak HR (HRpeak) or maximal HR (HRmax), depending on whether HRmax or only HRpeak was reached during the test conditions, and post-exhaustion HR at selected time points, i.e. 30s (HR30), 60s (HR60) and 120s (HR120) after the end of the tests [3 (link), 9 (link)]. Specifically, HRRec (i.e. ΔHRRec = peak/maximal HR minus post-exhaustion HR value) was reported in absolute values (beats·min-1) and as a percentage of HRpeak or HRmax (%HRRec) reached during the tests [23 (link)]. With the aim of evaluating the proposed levels of validity, data normalisation was performed using HRpeak and HRmax in either the untrained or trained states. Maximal HR (HRmax) was assessed as the maximal value reached across the testing conditions (i.e. Yo-Yo intermittent tests or the treadmill test for VO2max assessment), using a multiple approach, as suggested by Póvoas et al. [16 (link)], in recreational football. HRpeak refers to the maximal value reached during a testing condition that requires maximal effort, but that is below the maximal reached by the participant in all testing conditions.
The magnitude of HR60 was rated for clinical importance using the cut-off values suggested by Cole et al. [3 (link), 24 ]. Given the relatively active recovery observed post-exhaustion during the field tests (deceleration and spontaneous ambulation), abnormality was considered when HR60 was ≤12 beats·min-1 [3 (link), 8 (link)].
The intensity and duration of the exercise used to induce HRRec has been considered as a confounding variable [13 (link)]. With the aim of examining the interest in using intermittent endurance field tests in assessing HRRec, three intermittent versions of the Yo-Yo test were considered [17 (link)], namely levels 1 and 2 of the Yo-Yo intermittent endurance test (YYIE1 and YYIE2, respectively) and the Yo-Yo intermittent recovery test level 1 (YYIR1). The field test protocols were assumed to induce similar aerobic demands with different anaerobic involvement and time to exhaustion in order to stress different HRRec [13 (link), 17 (link)].
After the baseline (i.e. untrained status) VO2max and field testing, the participants engaged in a recreational football training intervention (2‒3 60-min weekly sessions) and were retested after 12 weeks of training to access the responsiveness of the selected variables (i.e., pre- and post-intervention). The training intervention was carried out according to the guidelines suggested by Krustrup et al. [18 (link), 19 (link), 25 (link)] for recreational football interventions with male participants.
The magnitude of HR60 was rated for clinical importance using the cut-off values suggested by Cole et al. [3 (link), 24 ]. Given the relatively active recovery observed post-exhaustion during the field tests (deceleration and spontaneous ambulation), abnormality was considered when HR60 was ≤12 beats·min-1 [3 (link), 8 (link)].
The intensity and duration of the exercise used to induce HRRec has been considered as a confounding variable [13 (link)]. With the aim of examining the interest in using intermittent endurance field tests in assessing HRRec, three intermittent versions of the Yo-Yo test were considered [17 (link)], namely levels 1 and 2 of the Yo-Yo intermittent endurance test (YYIE1 and YYIE2, respectively) and the Yo-Yo intermittent recovery test level 1 (YYIR1). The field test protocols were assumed to induce similar aerobic demands with different anaerobic involvement and time to exhaustion in order to stress different HRRec [13 (link), 17 (link)].
After the baseline (i.e. untrained status) VO2max and field testing, the participants engaged in a recreational football training intervention (2‒3 60-min weekly sessions) and were retested after 12 weeks of training to access the responsiveness of the selected variables (i.e., pre- and post-intervention). The training intervention was carried out according to the guidelines suggested by Krustrup et al. [18 (link), 19 (link), 25 (link)] for recreational football interventions with male participants.
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