# The Role of Cholinesterases in Post-Exercise HRV Recovery in University Volleyball Players
###### Abstract  
Some studies show interest in measuring heart rate variability (HRV) during post-exercise recovery. It is known that the parasympathetic system is relevant during this process, where one of the factors of this modulation is the interaction of acetylcholine and cholinesterase (ChE). However, the behavior of ChE and its relationship during recovery is little known; therefore, the objective of this study was to analyze the behavior of ChE and its relationship with recovery evaluated in HRV indicators in volleyball players. An exercise protocol with long-term and intermittent high-intensity phases was applied in nine volleyball players. HRV measurements were made, and blood samples were drawn to evaluate the ChE before exercise and after 24 and 48 h post-exercise. The results show a modification of the variables after exercises with respect to the baseline values (ChE: 1818.4 \(\pm\) 588.75 to 2218.78 \(\pm\) 1101.58; RMSSD: 42.64 \(\pm\) 12.86 to 17.72 \(\pm\) 12.55 (\(p\) \(<\) 0.05); SS: 8.76 \(\pm\) 1.93 to 21.93 \(\pm\) 10.05 (\(p\) \(<\) 0.01); S/PS Ratio: 0.32 \(\pm\) 0.14 to 3.26 \(\pm\) 3.28 (\(p\) \(<\) 0.01)), as well as recovery after 24 and 48 h with respect to postexercise (ChE: 1608.81 \(\pm\) 546.88 (\(p\) \(<\) 0.05) and 1454.54 \(\pm\) 580.45 (\(p\) \(<\) 0.01); RMSSD: 43.83 \(\pm\) 24.50 and 46.18 \(\pm\) 33.22 (\(p\) \(<\) 0.01); SS: 10.93 \(\pm\) 5.16 and 11.86 \(\pm\) 4.32 (\(p\) \(<\) 0.01); S/PS Ratio: 0.46 \(\pm\) 0.32 and 0.50 \(\pm\) 0.28 (\(p\) \(<\) 0.01)). ChE correlations (\(p\) \(<\) 0.001) were found with moderate (SS: \(r\) = 0.465) and large (RMSSD: \(r\) = \(-\)0.654; S/PS Ratio: \(r\) = 0.666) HRV indexes. In conclusion, ChE modifications are related to changes in HRV showing a very similar behavior in the case of the study subjects. cholinesterases; heart rate variability; autonomic recovery mechanisms; sympathetic-parasympathetic modulation; postexercise recovery +
Footnote †: journal: _Sci._  
0000-0002-0001-9999-2233-2233][PERSON]. [PERSON]  
0000-0002-0002-0002-0002-0002-0002-0002-0002-0002-0002-0002-002-0002-0002-0002-0002-A large number of studies have focused on measuring these variables in postexercise recovery and in determining how the duration and intensity affect them [5; 12; 13; 14]. However, there is a discrepancy in the use of these results, since, as far as we know, this tool has not been considered for evaluating the internal load [15]. Recovery is a complex interaction between the sympathetic and the parasympathetic system [5; 12], where the sympathetic influence is measured by the release of catecholamines and the activation of adrenergic receptors, and the parasympathetic influence is controlled by the release of acetylcholine in the vagus nerve increasing the parasympathetic tone [6]. However, during recovery, parasympathetic activity becomes relevant in returning the organism to a stable state [12; 16; 17]; thus, afferent vagal stimulation will lead to a reflex excitation of efferent vagal activity that inhibits sympathetic activity [6]. Parasympathetic control depends on the release of acetylcholine from the vagus nerve, which will bind to muscarinic receptors that hyperpolarize the cardiac muscle to decrease the slope of depolarization, resulting in a slowing of the heart rate [18; 19]. Efferent parasympathetic control is mediated by cholinergic signaling in the sinoatrial node, which is rich in acetylcholinesteraseicastase (AChE), which hydrolyzes acetylcholine after vagal impulses [6; 20; 21] that will maintain the parasympathetic tone [22; 23]. Several studies have analyzed the inhibition of AChE using pyridostigmine bromide to increase the parasympathetic activity, measuring it by HRV [20; 24; 25]. Since the cholinergic system is involved in the process of ANS modulation, its measurement could provide information on the regulation of the parasympathetic activity.