This study aimed to assess the effect of wearing a breathing apparatus during a simulated rescue intervention on psychophysiological responses and parasympathetic reactivation of firefighters. Thirty-four firefighters participated in this study which consisted of four experimental sessions conducted randomly: a maximal fitness test and three rescue interventions performed (a) with personal protective clothing (PPC); (b) with PPC and the full self-contained breathing apparatus (SCBA), including cylinder, full-face piece, and breathing regulator; and (c) with PPC and only the cylinder of the self-contained breathing apparatus (SCBAc). Physiological (heart rate [HR], breathing frequency [BF]) and perceptual (rating of perceived exertion [RPE]) responses were continuously collected during the three rescue interventions. Parasympathetic reactivation was assessed using HR recovery and variability indexes after experimental sessions. HR responses ranged between 63% and 95% of HR , and BF responses ranged between 22 and 55 breaths/min for the different activity tasks. Parasympathetic reactivation indexes were similar for the rescue interventions but lower than after the intermittent fitness test (P = 0.016 - P < 0.0001). Mean HR for both SCBAc (83.2 ± 4.1%HR ) and SCBA (83.1 ± 5.2%HR ) was higher in comparison with PPC (79.5 ± 5.3%HR ). RPE was higher for SCBA than for SCBAc which was higher than PPC. Mean BF for SCBA (34 breaths/min) was lower than PPC (40 breaths/min) and SCBAc (43 breaths/min). Based on HR, BF, and RPE, rescue interventions seem to be psychologically and physiologically stressful. Parasympathetic reactivation after PCC, SCBA, and SCBAc suggests that these conditions induce higher cardiac stress than the maximal fitness test. The study showed that SCBA increased psychophysiological perturbations.

To compare acute parasympathetic reactivation following usual training exercises, the acute post-exercise heart rate (HR) and heart rate variability (HRV) were analysed. Fourteen elite male handball players completed three separate sessions of 16-min small-sided games (SSGs), repeated sprints (RSs) consisting of two sets of six repetitions of a 25-m sprint with a 180° change of direction (12.5 m + 12.5 m) every 25 s and 40 min of handball-specific circuit training (CT, one brief action every 40 s). The HR was recorded during the exercises; HRV was assessed 10 min before and after exercise. The exercise HR was higher for SSGs than RSs and it was higher for RSs than CT. Comparison of the baseline and acute post-exercise HRV values showed that parasympathetic indices decreased following SSG (p < 0.01 – p < 0.0001; large effect size) and RS (p < 0.05 –p < 0.01; large effect size) interventions. For CT, recovery values remained similar to the baseline (small effect size). The comparison of the acute recovery period between exercise modalities showed that the root mean square of the successive differences (RMSSD) was lower for SSGs than RSs and CT. No difference in any HRV indices was observed between RSs and CT. Time-varying of RMSSD for successive 30 s segments during the 10 min recovery period showed lower values for SSGs than CT for all tested points; the progressive increase in the beat-to-beat interval was similar for all interventions. In conclusion, SSGs caused the greatest post-exercise vagal disruption and it is likely that CT is the exercise modality that least delays over-all recovery. These results might help coaches design better training sessions by understanding athletes’ recovery status after completing their conditioning exercises.

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Objective: To examine the effects on firefighters’ nocturnal cardiac autonomic activity and sleep quality of one on-call night without intervention and one on-call night with intervention. Methods: Thirteen firefighters completed three experimental nights: a control night (CON), an on-call night without intervention (0-INTER), an on-call night with one simulated intervention (1-INTER). Sleep parameters were determined from nocturnal heart rate variability (HRV), objective and subjective sleep quality. Results: Derived parasympathetic HRV indices were higher in CON compared with 0-INTER and 1-INTER (P < 0.05). Subjective sleep quality and total sleep time were decreased in 1-INTER compared with CON and 0-INTER (P < 0.01). Discussion: These results revealed that for firefighters, being on-call during the night with and without interventions disturbs cardiac autonomic activity. Objective and subjective sleep quality were disrupted when on-call nights were interrupted by simulated firefighting interventions.