Iyengar yoga increases cardiac parasympathetic nervous modulation among healthy yoga practitioners

Kerstin Khattab, Ahmed A Khattab, Jasmin Ortak, Gert Richardt, Hendrik Bonnemeier, Kerstin Khattab, Ahmed A Khattab, Jasmin Ortak, Gert Richardt, Hendrik Bonnemeier

Abstract

Relaxation techniques are established in managing of cardiac patients during rehabilitation aiming to reduce future adverse cardiac events. It has been hypothesized that relaxation-training programs may significantly improve cardiac autonomic nervous tone. However, this has not been proven for all available relaxation techniques. We tested this assumption by investigating cardiac vagal modulation during yoga.We examined 11 healthy yoga practitioners (7 women and 4 men, mean age: 43 +/- 11; range: 26-58 years). Each individual was subjected to training units of 90 min once a week over five successive weeks. During two sessions, they practiced a yoga program developed for cardiac patients by B.K.S. Iyengar. On three sessions, they practiced a placebo program of relaxation. On each training day they underwent ambulatory 24 h Holter monitoring. The group of yoga practitioners was compared to a matched group of healthy individuals not practicing any relaxation techniques. Parameters of heart rate variability (HRV) were determined hourly by a blinded observer. Mean RR interval (interval between two R-waves of the ECG) was significantly higher during the time of yoga intervention compared to placebo and to control (P < 0.001 for both). The increase in HRV parameters was significantly higher during yoga exercise than during placebo and control especially for the parameters associated with vagal tone, i.e. mean standard deviation of NN (Normal Beat to Normal Beat of the ECG) intervals for all 5-min intervals (SDNNi, P < 0.001 for both) and root mean square successive difference (rMSSD, P < 0.01 for both). In conclusion, relaxation by yoga training is associated with a significant increase of cardiac vagal modulation. Since this method is easy to apply with no side effects, it could be a suitable intervention in cardiac rehabilitation programs.

Keywords: Iyengar Yoga; cardiac rehabilitation; heart-rate-variability; yoga.

Figures

Figure 1.
Figure 1.
(a) Shavasana/corpse pose. (b) Purvottanasana on bench and support/intense stretch of the front of the body. (c) Ardha Chandrasana with a trestle/half moon standing pose. (d) Urdhva Dhanurasana with support/upward bow pose. (e) Bhismacharyasana with support/backbend named after Bhisma.
Figure 2.
Figure 2.
(a) Mean hourly results of RR-interval ECG-recordings among 11 Yoga students and a matched control group. The red arrow marks time of intervention of the yoga group (Yoga or Placebo). ***Yoga versus Placebo P < 0.001, **Yoga versus Control P < 0.01. (b) Mean hourly results of SDNN ECG-recordings among 11 Yoga students and a matched control group. The red arrow marks time of intervention of the Yoga group (Yoga or Placebo). ***Yoga versus Control P < 0.001, ***Placebo versus Control P < 0.001. (c) Mean hourly results of SDNNi ECG-recordings among 11 Yoga students and a matched control group. The red arrow marks time of intervention of the Yoga group (Yoga or Placebo). ***Yoga versus Placebo P < 0.001, ***Yoga versus Control P < 0.001. *Placebo versus Control P < 0.05. (d) Mean hourly results of SNN50 ECG-recordings among 11 Yoga students and a matched control group. The red arrow marks time of intervention of the Yoga group (Yoga or Placebo). **Yoga versus Placebo P < 0.01, **Yoga versus Control P < 0.01. (e) Mean hourly results of SDANN ECG-recordings among 11 Yoga students and a matched control group. The red arrow marks time of intervention of the Yoga group (Yoga or Placebo). **Yoga versus Placebo P < 0.01, ***Yoga versus Control P < 0.001, ***Placebo versus Control P < 0.001. (f) Mean hourly results of rMSSD ECG-recordings among 11 Yoga students and a matched control group. The red arrow marks time of intervention of the Yoga group (Yoga or Placebo). **Yoga versus. Placebo P < 0.01, **Yoga versus Control P < 0.01, *Placebo versus Control P < 0.05. (g) Mean hourly results of TI ECG-recordings among 11 Yoga students and a matched control group. The red arrow marks time of intervention of the Yoga group (Yoga or Placebo). ***Yoga versus Placebo P < 0.001, ***Yoga versus Control P < 0.001, *Placebo versus Control P < 0.0.

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