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Variation of heart rate irregularity, heart rate and respiratory rate as a function of mental load consisting largely of perception of danger.
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In a previous research heart rate irregularity had been proposed as a measure for mental load caused primarily by information handling (binary choice tasks). In the experiments with flight simulators (mainly information handling) this proposal was verified and to some extend corroborative evidence was given.
However, it was also found that heart rate reacted significantly to the type of mental load used in these experiments.
When defining mental load distinction is made between mental load caused by information handling, emotion and tension. Heart rate irregularity had been proposed as the typical measure for mental load by information handling.
It follows that when mental load is caused by "emotion" and/or tension, with information handling minimized, one should expect heart rate irregularity to be less reactive.
To verify this assumption an experiment was conducted were mental load consisted of various levels of "tension", information handling being minimal.
It was hypnotized that in this experiment heart rate would have a greater differentiating power between load levels than SA and RR, with the magnitude of W² as a criterion.
Material and methods.
To achieve differences in mental load created mainly by tension and with information handling minimal, parachute jumping was used as a stressor. The (dependent) physiological variables were HR SA, and RR ( on ground only ).
The independent variable had 4 levels, consisting of situations found in parachute jumping. The levels, in order of supposedly increasing mental load were : 1. rest value, relaxed at the ground at the end of the day; 2. rest value, relaxed on ground, before jumping; 3. registration in aircraft before subjects jump run; 4. registration during subjects jump run.
A subjective ratting of the 4 situations on a seven points scale was obtained after the final registration.
A high degree of experimental control was achieved in this experiment, notably in standardization of sample periods ( e.g. same stimulus always preceding and terminating period, and irrelevant variables being similar in all samples).
Twelve subjects took part, average age 21.1 years, each was measured approximately on 3rd and 4th jump.
figure 6 shows HR and SA as a function of mental load. ANOVAR values are given in table 1.
Figure 7 shows the curve of the subjective scale.
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FIGURE 6. FIGURE 7.
F P W²
HF 123,95 0,001 0,71
SA 36,86 0,001 0,46
Table 2 gives ANOVAR values for comparison of ground values only ( e.g. before jump and after jump on ground ). This comparison includes RR.
F P W²
HF 34,32 0,001 0.20
SA 1,52 n.s.
RR 0,04 n.s.
P.M. correlation coefficient between subjective scale values and HF and SA are 0,97 and - 0,88 respectively. Only the HF correlation is significant (p < 0.025).
The results show that HF is the most sensitive parameter for mental load caused by tension only. This conclusion is supported by 3 significant observations
1. the higher W² value ( Table 1 ).
2. only parameter differentiating between ground sessions only ( Table 2 )
3. only parameter with significant correlation with subjective scale.
Comparison of the results with the flight simulator experiments following below shows reverse order, which was predicted on the assumption that sinus arrhythmia is especially sensitive for mental load involving information handling.
Validation of constructs II "Main Page"
Copyright J. P. Krol ©
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