Comparison of Yoga Versus Sports Activities in Improving Cardiac Autonomic Function in Adolescents with Perceived Anxiety: A Comparative Randomized Pilot Study

INTRODUCTION

The educational environment in India is renowned for fostering a culture of academic excellence, motivating Indian students to pursue high achievement. This pursuit often results in heightened levels of stress.^[1,2] Medical college students, in particular, face demanding academic requirements that increase stress levels, impacting their overall health and well-being.^[3] Unlike typical adolescent worries, stress poses a more substantial concern for medical students.^[4] According to the Job Demand-Control-Support model, stress escalates in high demand, low self-control, and low social support.^[5] In the academic domain, stress can detrimentally affect psychological health, potentially leading to mental distress and impaired cognitive function and learning.^[6] The absence of treatment for an extended period can lead to irreversible changes in autonomic functions, which can cause significant alterations in cardiovascular functions.

Cardiovascular diseases significantly burden public health in both developed and developing nations.^[7] Various cardiovascular ailments, including hypertension, arrhythmias, and metabolic dysfunction, often originate from an autonomic nervous system (ANS) imbalance.^[8,9] Heart rate variability (HRV) is a non-invasive method for assessing cardiac autonomic activity. This parameter reflects the equilibrium between sympathetic and parasympathetic control of the heart, measured through normal-to-normal (NN) intervals. Reduced parasympathetic activity contributes to diminished HRV, a critical clinical indicator for hypertension and coronary artery disease.^[10,11]

Yoga contributes to establishing equilibrium in ANS activity, as indicated by sympathovagal balance, thereby demonstrating an enhancement in HRV. Yoga elicits the relaxation response, physiologically antithetical to the stress or fight-or-flight response. Consequently, this elicits a decline in sympathetic nervous system activity while enhancing parasympathetic activity.^[12] In contrast, activities such as Dodgeball engage the sympathetic nervous system, triggering the body’s fight or flight response. Despite this, such activation can still reduce stress through several mechanisms. Physical activities, including Dodgeball participation, lead to endorphins release, acting as natural mood enhancers. These substances are crucial in combating stress and enhancing overall mood.^[13] The primary aim of this research was to evaluate the effects of yoga and sports activities on cardiac autonomic function in adolescents who are experiencing anxiety.

MATERIAL AND METHODS

The prospective interventional study was conducted at the Department of Allied Health Science (AHS) within a private medical college and hospital in Chennai, Tamil Nadu, following full approval from the Institutional Scientific and Ethics Committee for the clinical protocol. This study engaged forty adolescent students, aged 19–24, from a paramedical college, all of whom were identified as experiencing perceived anxiety and had no prior yoga experience. Utilizing the depression, anxiety, and stress scale (DASS-42) questionnaire alongside the Welltory app (version 3.2.3), we successfully identified students with perceived anxiety, selecting those who displayed moderate to severe levels for participation. Participants who regularly engage in athletic activities, smoke, have a history of alcohol dependency, are experiencing acute illnesses, or have recently undergone surgical procedures were definitively excluded from the study. Furthermore, individuals diagnosed with endocrine disorders, cardiovascular conditions, chronic obstructive pulmonary disease, or asthma, as well as those who engage in more than 1 h of regular physical exercise, were also excluded from maintaining a strictly controlled study environment. After thorough baseline testing confirmed a normal body mass index (BMI), students were randomly assigned to either the yoga or sports group, with 20 participants in each. Before the experiment, all participants provided comprehensive written informed consent and received detailed instructions on the study procedures. Data collection occurred in the AHS Skill laboratory, where participants utilized cutting-edge Photoplethysmography (PPG) technology. The Welltory app, a specialized smartphone application designed to measure HRV through PPG technology, was integral to our data-gathering process. PPG technology uses a light-emitting diode, commonly a smartphone camera flash, to assess heart rate (HR) by analyzing skin illumination and collecting HRV time domain data (standard deviation of the normal-to-normal intervals [SDNN], root mean square of successive differences between successive normal heartbeats [RMSSD]).^[14] Participants in the study received detailed and explicit instructions from experts regarding the maintenance of their regular sleep routines and guidance to refrain from consuming caffeine and alcohol before the assessments. The evaluations were systematically scheduled for the morning hours, followed by a light breakfast, stipulating that participants consume this meal at least 2 h before the assessments. Participants were instructed to empty their bladders before the start of the recordings. Each participant completed the DASS-42 questionnaire confidently before and after the 4-week intervention.^[15] During HRV measurements, participants maintained a supine position with their eyes open to ensure the highest accuracy in the data collected. This standardized protocol was consistently applied for baseline measurements throughout the 4-week study, encompassing 2 weekly sessions.

Randomization and blinding/masking

Three hundred and twenty potential subjects were screened to assess eligibility for the study; however, 270 individuals did not fulfill the established criteria. As a result, 50 participants remained, randomly assigned to one of two groups: the yoga group, consisting of 25 participants, and the sports group, comprising 25 participants. During the follow-up phase, five participants from each group were withdrawn from the study due to health-related issues and non-compliance with the prescribed training sessions [Figure 1]. The allocation process was implemented using a simple randomization technique comparable to a coin toss, ensuring an unbiased selection methodology. In the current study, participants were informed of their group assignments, while the investigator remained unaware of the identities of the group members, thereby achieving a double-blind design. Certified and qualified yoga instructors facilitated the sessions, while experienced physical education trainers supervised the sports sessions. A skilled medical physiologist evaluated the parameters of HRV to mitigate potential observer discrepancies.

Close

Figure 1:

Flow chart diagram.

Export to PPT

RESULTS

The study recruited 40 participants who met the established inclusion and exclusion criteria. The participants had a mean age of 19.4 years, with a SD of ± 0.6 years, and were randomly allocated into two distinct groups: one group engaged in yoga (n = 20) and the other participated in sports (n = 20). The mean age (SD) was 19.4 ± 0.6 years in the yoga group and 19.5 ± 0.6 years in the sports group. No significant differences were found between the yoga and sports groups regarding age, height, weight, BMI, and oxygen saturation (SpO₂), suggesting a similar distribution of subjects in both groups (P > 0.05) [Table 1].

Result of time domain of HRV in yoga group

The initial SDNN (ms) value for the yoga group was 266.1 ± 85.9 (ms). Subsequent SDNN values at the 4^th and 8^th sessions were recorded as 147.60 ± 109.06 and 136.10 ± 111.83 (ms), respectively. A statistically significant reduction in SDNN (ms) values was observed in the yoga group following the eighth session compared to baseline data [Table 2 and Figure 2].

Table 2: Impact of yoga on heart rate variability measurement.

Variables	Mean±SD	95% confidence interval of the difference		T-statistic	Degree of freedom (df)	P-value
		Lower	Upper
SDNN
Pre versus S4	266.10±85.99	51.689	185.311	3.71	19	0.00*
	147.60±109.06
S4 versus S8	147.60±109.06	−57.141	80.141	0.35	19	0.73
	136.10±111.83
Pre versus S8	226.10±85.99	79.79	180.206	5.42	19	0.00*
	136.10±111.83
Mean RR
Pre versus S4	913.30±150.69	12.99	224.80	2.350	19	0.03*
	794.40±161.78
S4 versus S8	794.40±161.78	−74.85	100.05	0.302	19	0.76
	781.80±139.29
Pre versus S8	913.30±150.69	57.19	205.81	3.704	19	0.00*
	781.80±139.29
RMSSD
Pre versus S4	216.75±131.135	−16.47	168.67	1.721	19	0.10
	140.65±106.35
S4 versus S8	140.65±106.35	−78.52	100.82	0.260	19	0.79
	129.50±141.85
Pre versus S8	216.75±131.135	20.43	154.06	2.733	19	0.01*
	129.50±141.85
PNN50
Pre versus S4	68.85±24.515	−4.87	28.87	1.488	19	0.15
	56.85±32.218
S4 versus S8	56.85±32.218	−11.56	29.06	0.902	19	0.37
	48.10±32.148
Pre versus S8	68.85±24.515	5.50	35.99	2.849	19	0.01*
	48.10±32.148
MXDMN
Pre versus S4	0.85±0.366	0.259	0.7400	4.359	19	0.00*
	0.35±0.48
S4 versus S8	0.35±0.48	−0.288	0.188	−0.438	19	0.66
	0.400±0.50
Pre versus S8	0.85±0.366	0.211	0.688	3.943	19	0.00*
	0.400±0.50
MODA
Pre versus S4	714.75±185.09	−146.64	71.14	−0.726	19	0.47
	752.50±152.58
S4 versus S8	752.50±152.58	−47.62	97.62	0.721	19	0.48
	727.50±108.18
Pre versus S8	714.75±185.09	−112.25	86.75	−0.268	19	0.79
	727.50±108.105
Heart rate
Pre versus S4	69.55±13.43	−18.74	0.748	−1.93	19	0.06
	78.55±16.44
S4 versus S8	78.55±16.44	−9.63	8.532	−0.127	19	0.90
	79.10±13.52
Pre versus S8	69.55±13.43	−15.95	−3.14	−3.122	19	0.00*
	79.10±13.52

Bold and * indicates: Statistically significant at P<0.05, Pre: Pre intervention, S: Sessions, SDNN: Standard deviation of the NN intervals, RMSSD: Root mean square of successive differences between successive normal heartbeats, SDNN: Standard deviation of NN intervals, Mean RR: The average time between heartbeats in milliseconds, RMSSD: Root mean square of successive RR interval differences, PNN50: Percentage of successive RR intervals that differ by more than 50 ms, MXDMN: The difference between the maximum and minimum measured RR interval, MODA: Median of RR intervals.

Close

Figure 2:

Impact of yoga on heart rate variability parameters. SDNN: Standard deviation of the NN intervals, RMSSD: Root mean square of successive differences between successive normal heartbeats, MXDMN: The difference between the maximum and minimum measured RR interval, Mean RR: The average time between heartbeats in milliseconds, PNN50: Percentage of successive RR intervals that differ by more than 50 ms, MODA: Median of RR intervals.

Export to PPT

Result of time domain of HRV in sports group

The initial SDNN (ms) value for the sports group was 202.20 ± 50.17(ms). Subsequent measurements at the 4^th and 8^th sessions indicated 98.90 ± 99.643 and 144.90 ± 139.63 (ms) values, respectively. SDNN (ms) values were reduced following the eighth session compared to the baseline data [Table 3 and Figure 3].

Table 3: Impact of sports on heart rate variability measurement.

Variables	Mean±SD	95% confidence interval of the difference		T-statistic	Degree of freedom (df)	P-value
		Lower	Upper
SDNN
PRE versus S4	202.20±50.177	52.34	154.25	4.24	19	0.09
	98.90±99.643
S4 versus S8	98.90±99.643	−130.08	38.08	−1.14	19	0.26
	144.90±139.63
PRE versus S8	202.20±50.177	−10.34	124.94	1.77	19	0.09
	144.90±139.63
Mean RR
PRE versus S4	653.60±101.09	−36.24	133.74	1.200	19	0.24
	604.85±182.855
S4 versus S8	604.85±182.855	−61.99	175.09	0.998	19	0.33
	658.55±135.585
PRE versus S8	653.60±101.09	−81.69	71.79	−0.135	19	0.89
	658.55±182.855
RMSSD
PRE versus S4	67.30±49.59	−65.72	65.82	0.002	19	0.99
	67.25±118.60
S4 versus S8	67.25±118.60	−144.06	40.86	−1.16	19	0.25
	118.85±127.96
PRE versus S8	67.30±49.59	−100.99	−2.101	−2.18	19	0.04*
	118.85±127.96
PNN50
PRE versus S4	37.35±16.33	5.437	36.76	2.82	19	0.01*
	16.25±26.88
S4 versus S8	16.25±6.88	−38.801	5.601	−1.56	19	0.13
	32.85±31.86
PRE versus S8	37.35±316.33	−12.803	21.803	0.544	19	0.59
	32.85±31.86
MXDMN
PRE versus S4	0.200±0.41	−18.95	5.95	−1.09	19	0.28
	6.70±26.80
S4 versus S8	6.70±26.80	−6.28	18.88	1.04	19	0.30
	0.400±0.50
PRE versus S8	0.200±0.41	−0.52	0.125	−1.28	19	0.21
	0.400±0.50
MODA
PRE versus S4	645.0±65.69	63.68	14108	5.50	19	0.00*
	542.25±61.37
S4 versus S8	542.25±61.37	−87.36	75026	−0.15	19	0.87
	548.30±174.85
PRE versus S8	645.0±65.69	6.449	186.95	2.24	19	0.03*
	548.30±174.85
HR
PRE versus S4	108.50±7.21	−17.77	61.77	1.15	19	0.26
	86.50±83.82
S4 versus S8	86.50±83.82	−47.753	28.353	−0.53	19	0.60
	96.20±21.41
PRE versus S8	108.50±7.21	1.785	22.81	2.44	19	0.02*
	96.20±21.41

Bold and * indicates: Statistically significant at P<0.05, Pre: Pre intervention, S: Sessions, SDNN: Standard deviation of the NN intervals, RMSSD: Root mean square of successive differences between successive normal heartbeats, HR: Heart Rate, RR: The average time between heartbeats in milliseconds, RMSSD: Root mean square of successive RR interval differences, PNN50: Percentage of successive RR intervals that differ by more than 50 ms, MXDMN: The difference between the maximum and minimum measured RR interval, MODA: Median of RR intervals.

Close

Figure 3:

Impact of sports on heart rate variability parameters. SDNN: Standard deviation of the NN intervals, RMSSD: Root mean square of successive differences between successive normal heartbeats, MXDMN: The difference between the maximum and minimum measured RR interval, Mean RR: The average time between heartbeats in milliseconds, PNN50: Percentage of successive RR intervals that differ by more than 50 ms, MODA: Median of RR intervals.

Export to PPT

DISCUSSION

This study significantly contributes to the literature by assessing the effects of traditional and contemporary exercise methods on HRV, an area that remains underexplored. The findings reveal that no statistically significant differences were observed in the SDNN or the RMSSD in sports activity. In contrast, significant alterations were observed in the SDNN, mean RR interval, mean HR, RMSSD, MxDMN, and pNN50 among the participants who practiced yoga. After yoga practice, a marginal increase in HR was evident. Decreased overall HRV (SDNN) following the practice indicates a positive health outcome. Following a yoga session, pNN50 was significantly reduced, indicating an enhancement in the adaptability of the ANS. This improvement is associated with increased cardiovascular fitness, lower stress levels, and a comprehensive enhancement in overall health.

In addition, the decrease in RMSSD and MxDMN measurements reflects an adaptive response of the cardiovascular systems to external stressors, indicating flexible autonomic regulation and effective vagal activity. This adaptation may be attributed to heightened vagal tone or sympathetic withdrawal after implementing yoga practices. Ultimately, these results imply that participants in the yoga group manifested heightened parasympathetic tone following yoga therapy compared to their counterparts in the sports group.

Following sports participation, HRV reflects sympathetic dominance during physical activity to address heightened oxygen and nutrient requirements. After exercising, parasympathetic activity increases as the body recovers. In conclusion, changes in HRV metrics after physical exertion indicates a shift from effort to recovery. This highlights a more balanced autonomic state led by the parasympathetic nervous system as the body seeks to regain equilibrium.

The yoga and sports groups exhibited increased HR, indicating sympathetic activation and muscle exertion. These findings align with those of Bhavanani et al.,^[16] who similarly documented increased HR pre- and post-repetitive yoga practices. SDNN, an indicator of overall HRV, was notably changed during Yoga, corroborating the observations of Malhotra et al.,^[17] who noted significant changes in SDNN following yoga practice. The ANS effectively manages stress after repeated yoga sessions, as indicated by reduced SDNN values in the yoga group. This aligns with Farinatti et al.,^[18] who found decreased SDNN post-exercise due to combined parasympathetic and sympathetic modulations. Furthermore, the decrease in RMSSD and MxDMN measurements after yoga corresponds to similar results observed in an interventional study conducted by Pal et al.^[19] in Puducherry, India, where cardiovascular autonomic functions of apparently healthy, male medical students were assessed following a short-term relaxation therapy regimen. The results demonstrated an improvement in autonomic balance toward parasympathetic activity after a short-term practice of relaxation therapy.

Similar studies have been reported by An et al.,^[20] Patra and Telles,^[21] and Vempati and Telles^[22] which have demonstrated that yoga-based guided relaxation techniques, such as cyclic meditation and Shavasana, can modulate HRVs in a parasympathetic manner. A study done by Naswa et al. suggests that the inclusion of Rajyoga meditation along with conventionally given cardiac rehabilitation enhanced metabolic resilience with lowered resting metabolism and enhanced recovery post-surgery in children operated on for congenital heart disease. There was an improvement in the psychological adjustment and behavior of adolescents.^[23]

CONCLUSION

The study observed a significant improvement in cardiac autonomic function, indicating that yoga positively impacts an individual’s overall health status. These effects were notably evident after a short duration of yoga practice. Long-term engagement in yoga could mitigate the risk of physiological and psychological ailments and enhance overall quality of life. Yoga is a non-pharmacological treatment strategy for individuals experiencing stress. However, the sports intervention improved the body’s ability to manage stress. At the same time, yoga therapy resulted in a heightened parasympathetic tone compared to the sports intervention.