EFFICIENCY OF HEART RATE VARIABILITY BIOFEEDBACKIN ADOLESCENTS AGED 15-16 YEARS AFTER PHYSICAL EXERCISE IN A COLD ENVIRONMENT
Short-term biofeedback (BF) training provides effective restoration of the cardiovascularsystem (CVS) after physical exercise. Purpose: assessment of CVS reactivity in adolescents aged15-16 years during a heart rate variability (HRV) BF session following a speed-strength exercise (thrice-repeated standing long jump) in the open air (from -1 to -10 °C). Materials and methods. Healthyadolescents were examined: an experimental group ( <i>n</i> = 15) subject to HRV BF training (3 min) usingVarikard equipment (Ramena, Russia) in order to increase the total HRV power and a control group( <i>n</i> = 12). The following stages of recording HRV and blood pressure indicators were singled out:background (initial indicators), period immediately after physical activity, and recovery period with HRVtraining (experimental group) or being at rest (control group). Results. During the recovery periodafter a HRV BF session, subjects from the experimental group showed significantly higher total HRVpower compared with the control ( <i>p</i> = 0.04). In experimental group individuals with a heart rate of lessthan 90 bpm against the background of its increase during BF training, stress index did not changesignificantly. In subjects with tachycardia (above 90 bpm), heart rate and stress index remained elevatedat all stages. Conclusion. Short-term BF training (3 min) after a speed-strength exercise in a coldenvironment increases the total HRV power in adolescents; the degree of reduction in sympatheticresponse depends on the initial heart rate level. The relative increase in heart rate during HRV BFtraining after physical exercise in a cold environment indicates the need for a longer BF session (over 3 min) in order to achieve a more pronounced influence of vagal effects on the heart rhythm.