KKruskal Wallis Test, FFriedman
Test, *p<0.05. Note: Different capital letters in the lines
indicate the difference between groups.
DISCUSSION
In the study, the effect of transcutaneous auricular vagus nerve
stimulation applied for 4 days on healthy young individuals on pain,
fatigue, blood pressure, heart rate, distance covered, lactic acid level
and autonomic nervous system was investigated. Volunteers participating
in the study were randomly divided into 3 groups as control, unilateral
stimulation and bilateral stimulation, with equal numbers of males and
females.
In the study, pain was evaluated with a numerical pain rating scale,
fatigue with a numerical fatigue rating scale, heart rate and blood
pressure with a digital sphygmomanometer, distance covered with a
magnetic exercise bike, lactic acid level with lactate plus, and
autonomic nervous system with Polar H10 device. During the study,
evaluation was made before and after cycling exercise, before and after
vagus nerve stimulation (VSS).
Cook et al. used a numerical pain scale to evaluate pain after cycling
exercise in 16 African-American women with a history of parental
hypertension (Cook, Jackson, O’connor, & Dishman, 2004). In the study
of Jameson and Ring in which they compared the effect of different
wattage and cadence of cycling exercise, they evaluated pain with a
numerical pain scale (Jameson and Ring, 2000). In the study evaluating
the pain caused by the maximum and sub-maximum cycling exercise in the
leg muscle, it was compared with the numerical pain scale (Motl,
Gliottoni, & Scott, 2007). As in our study, numerical pain scale was
used as the evaluation method in the literature.
In another study evaluating pain perception after resistant exercise,
after exercise and rest period were compared. In addition to pain,
anxiety, body awareness, heart rate, systolic and diastolic blood
pressure were also evaluated (Koltyn & Arbogast, 1998). In a study
conducted in patients with osteoarthritis, in a study investigating the
effect of swimming and cycling exercise on vascular function, pulse,
systolic and diastolic blood pressure were also evaluated in addition to
blood analysis (Alkatan et al., 2016). Similar to the examples in the
literature, in addition to the evaluation methods included in our
hypothesis, the participants’ pulse, systolic and diastolic blood
pressure were measured with a digital blood pressure monitor.
In a study consisting of 18 healthy adult male geneticists, the level of
fatigue was regularly questioned during cycling exercise and rest, and a
numerical fatigue scale was used for this (Micklewright, St Clair
Gibson, Gladwell, & Al Salman, 2017). Another study found that
high-intensity cardiorespiratory and strength exercises reduced fatigue
and sensory distress in patients with axial spondyloarthritis. Numerical
fatigue scale was used to evaluate fatigue in the study (Sveaas, Berg,
Fongen, Provan, & Dagfinrud, 2018). In our study, the fatigue level of
the participants was evaluated with a numerical fatigue scale.
14 healthy individuals participated in a study investigating the effect
of heart rate variability on biofeedback, autonomic function, and
functional connectivity of the prefrontal cortex. In the study, the
autonomic nervous system was evaluated with the Polar H10 device and the
Elite HRV program (Schumann, Köhler, de la Cruz, Brotte, & Bär, 2020).
The effect of training load applied at different levels on heart rate
variability and running performance was investigated in the study, which
included 7 athletes in the Olympic level rugby team. Polar H7 device and
Elite HRV program were used to evaluate heart rate variability and
autonomic nervous system (Flatt and Howells, 2019). Similar to the
examples in the literature, Polar H10 device and Elite HRV program were
used in our study.
The lactate scout device was used in the study evaluating the lactate
concentration in the blood of 17 Polish sprinters competing in the elite
100 meters category (Kawczyński et al., 2015). 14 people participated in
the study investigating the acute effect of peristaltic pneumatic
compression. In the study, the repeated anaerobic exercise performance
of the participants and the level of lactate in the blood were
investigated. The lactate level in the blood was evaluated with the
Lactat scout device (Martin, Friedenreich, Borges, & Roberts, 2015). In
our study, this device was used to examine the lactate level. In
addition, it provided practicality during measurements.
Uthman et al. published a 12-year observation in their study
investigating the effectiveness of VSS in patients with epilepsy. 28
people with persistent epilepsy participated in the study. During the
treatment, 2 participants could not complete due to traffic accident and
cancer. The VSS was performed using a device implanted in the neck.
Seizure numbers were noted over the 12-year observation period from the
initial moment. The side effects of the application were found to be
mild to moderate. The mean seizure frequency was found to decrease by
26% after 1 year, 30% after 5 years, and 52% after 12 years with VSS
(Uthman et al., 2004). Rush et al. investigated the effect of VSS on
treatment-resistant depression. In this multicenter study, 30 patients
who did not benefit from at least two drug trials were included. The
application was made with a device implanted in the neck while using the
drug. The study, in which the control group was included, lasted 10
weeks. In the study, it was concluded that VSS has as much effects as
antidepressants in treatment-resistant depression (Rush et al., 2000).
Ten people participated in a pilot study on treatment-resistant anxiety.
The patients continued to use their medications for 12 weeks. After the
VSS 2-week stimulation adjustment period, the stimulation parameters
were fixed for the remaining 8 weeks of the acute study. There was a
50% or greater improvement in the Hamilton anxiety scale for all
patients and 25% or greater improvement in the Yale-Brown
obsessive-compulsive scale for patients with obsessive-compulsive
disorder (George et al., 2008). It has been used in many diseases in the
literature, and its use tends to expand as its success increases.
16 people participated in Koltyn et al.’s study evaluating pain
perception following aerobic exercise. As an exercise, a bicycle
ergometer was used for 30 minutes. A 30-minute rest period was applied
after the exercise. In the study, pain was evaluated with a numerical
pain scale and an algometer. There was an increase in pain perception
after an acute exercise. However, there was a decrease in pain
perception during exercise compared to the rest period. (Koltyn,
Birklein, Stefan and Handwerker, 2000). In our study, the second
measurement value was higher than the first measurement value every day
in all groups. This is due to the increased perception of pain after
exercise. This situation is similar to the literature.
Bush et al. conducted an experimental study investigating the effect of
transcutaneous VSS on pain perception. It was evaluated with a
quantitative sensory test including the tonic heat pain paradigm in 48
healthy volunteers. Each subject attended two experimental sessions in a
random order with stimulation or sham stimulation on different days. The
stimulated group significantly reduced the level of pain during
continuous application of painful heat for 5 minutes compared to the
sham group. No related changes in cardiac or respiratory activity or
clinically relevant adverse effects were observed during administration
(Busch et al. 2013). Ten healthy volunteers participated in an
experimental study investigating the effect of VSS applied from the left
cervical region on pain. Pain is created by heat, pressure, and
short-term pulsing. Pain was evaluated with a visual analog scale. As a
result of the study, it was found that VSS was effective in reducing
pain in humans (Kirchner et al., 2000). In all groups, the 3rd
measurement value is lower than the 2nd measurement value. This shows
that pain decreased in all groups. However, the values in the TVSS and
control groups are higher than those in the DVSS group. In other words,
VSS is effective in relieving pain. However, when we compare the control
and TVSS groups, there is no difference in the effect on pain.
The acute effects of two types of aerobic exercise on maximum strength
and endurance were investigated. Eight men with a high level of physical
activity participated. It has a randomized design in which all subjects
complete both control and experimental conditions. Each session was held
1 week apart. The study revealed that both aerobic and strength
exercises produced significant peripheral fatigue in the same muscle
group (De Souza et al., 2007). In a study investigating the acute effect
of aerobic exercise on mood, 32 female students aged 18 to 23
participated in a single-session experiment in which they performed two
8-minute high-intensity exercise trials and two 8-minute low-intensity
exercise trials. Fatigue level was evaluated with borg fatigue scale. In
general, they found that high-intensity exercise leads to an increase in
tension/anxiety and fatigue (Steptoe and Cox, 1988). In our study, the
second measurement values of the participants in all groups were higher
than the first measurement values. As in the literature, we have
observed that exercise acutely increases fatigue.
A study was conducted investigating the effect of noninvasive VSS on
fatigue and immune responses in patients with primary Sjögren’s
syndrome. 15 female subjects participated in the study. The VSS was
applied from the cervical region in a non-invasive manner, twice daily
over a 26-day period. Fatigue-related data were collected on days 7 and
28 by fatigue profile index and visual analog scale. They found that the
vagus nerve may play a role in the regulation of fatigue and immune
responses in patients with primary Sjögren’s syndrome and may reduce the
clinical symptoms of VSS related to fatigue and sleep problems (Tarn,
Legg, Mitchell, Simon, & Ng, 2019). A randomized controlled clinical
trial was conducted investigating the effect of auricular VSS for
insomnia. 72 subjects from three different hospitals participated.
Participants were randomly divided into 2 groups as control and
stimulation. Fatigue level was evaluated with the Flinders fatigue
scale. It was concluded that VSS relieves fatigue, improves
participants’ quality of life and other accompanying symptoms such as
depression and anxiety (Jiao et al., 2020). Similar to the literature,
as in our study, fatigue scores obtained from the control group were
higher than the TVSS and DVSS groups. This shows that VSS is effective
in reducing fatigue. However, the superiority of the single and double
ear application over each other was not observed.