Chemie | Biochemie | Medizin
Andri Gitz, 2002 | Malans, GR
Heart failure is one of the most common causes of death in developed countries. It is often linked to the ability to cope with stress. Heart rate variability (HRV) is an indicator of cardiac health. This investigation focuses on the question whether the ability to cope with physical or with mental stress is more critical to heart rate variability at rest. The present research tries to clarify differences and similarities in immediate HRV. The heart rate variability of nine healthy male students, 16 to 19 years of age, was measured during rest and during standardized physical and mental test phases. In addition, participants were asked about the perceived exertion. The tests were conducted on two consecutive days under laboratory conditions. In conclusion, this investigation suggests that HRV is impacted by stress, and the study thus supports its use for the objective assessment of psychological health and stress.
The research questions of this study are the following: (1) Is heart rate variability at rest better explained by the ability to cope with physical or with mental stress? (2.1) Are there any differences within the test participants during physical tasks, compared to resting values? (2.2) Are there any differences within the test participants during mental tasks, compared to resting values? (3.1) Does the mean RR correlate to the mean HR during both activities? (3.2) Are the two resting phases correlated? (3.3) Does the rate of perceived exertion during the physical test correlate with heart rate variability during the physical test? (3.4) Does the rate of perceived exertion after resting correlate with the resting heart rate variability?
The heart rate variability of nine healthy male students, 16 to 19 years of age, was measured during rest and during standardized physical and mental tests. In addition, participants were asked about the perceived exertion. The tests were conducted on two consecutive days under laboratory conditions at the University of Applied Sciences SUPSI in Landquart. HRV was measured with an ECG-accurate heart strap during all phases. The testing procedure included 2 phases on two consecutive days. After the 20-minute resting phase, either a mental (ANAM test) or a physical test (walking on a treadmill) was assessed. ANAM stands for Automated Neuropsychological Assessment Metrics and has been developed to assess human factors such as visual memory capacity, reaction time and concentration. The data were analyzed with the Kubios Premium software.
Test subjects with a lower pulse and high heart rate variability during physical stress showed a higher heart rate variability during rest. Mean RMSSD (parasympathetic indicator) during physical stress was on average 82 percent lower than at rest (10 ms during physical stress vs. 55 ms at rest). Mean RMSSD during mental stress was on average 12 percent lower than at rest. Significant differences in both time domain parameters (SDNN and RMSSD) between mental activity and physical activity are visible. The SDNN values as well as the RMSSD values in the mental activity are lower than in the mental activity. A decrease of RR-values is correlated with higher Borg scale values. No correlation has been found between the mean RR intervals during the resting phase and values of perceived exertion at the beginning of the physical test.
There is a remarkable difference in heart rate variability between physical and mental activity, with physical effort resulting in a lower heart rate variability than mental effort. This remarkable difference seems to be induced by a greater activity of the parasympathetic nervous system during mental activities. Further, the investigation was able to show that the differences between a rest situation and a physical stress situation were significant. One explanation may be that the sympathetic nervous system dominates or has a stronger influence on the parasympathetic nervous system during physical activities. The correlation of the rate of perceived exertion with heart rate variability might be used as an objective measurement of exhaustion.
Measuring heart rate variability is a useful tool to collect data of cardiac modulations by the sympathetic and the parasympathetic components of the autonomous nervous system. Physical activity has a high sympathetic activation of the autonomous nervous system, whereas mental activity is affected by sympathetic and parasympathetic activation. There is a remarkable difference in heart rate variability between physical and mental activity in young healthy students. Physical effort results in a lower heart rate variability than mental effort.
Würdigung durch die Expertin
Der zunehmende Leistungsdruck in der modernen Gesellschaft fordert seinen Tribut. Die (oftmals stressinduzierte) Herzinsuffizienz gilt als eine der häufigsten Todesursachen in der westlichen Welt. Andri Gitz vergleicht in seiner Arbeit die Bewältigung von mentalen und physischen Stresssituationen anhand der Veränderung der Herzfrequenzvariabilität (HRV), welche als Gesundheitsindikator des kardiovaskulären Systems dient. Mit seinem Engagement für diese interdisziplinäre Thematik hat er aufgezeigt, dass die Forschung auf diesem Gebiet einen vielversprechenden Ansatz für die Zukunft bietet.
Evangelische Mittelschule Schiers
Lehrer: Manuel Voellmy