# Associations between left atrial indices and cardiorespiratory and muscular fitness among physically active military personnel

## TL;DR

This study explores how left atrial measurements relate to physical fitness in military personnel, finding specific correlations with running, push-up, and sit-up performance.

## Contribution

The study introduces novel composite left atrial indices that correlate with different types of exercise performance in physically active individuals.

## Key findings

- The LAVI-to-LASI_v ratio was the best overall correlate for running, push-up, and sit-up performance.
- The LAVI-to-mitral E/e′ ratio was the strongest unique correlate for 3-km running performance.
- Top runners had lower stiffness and higher LAVI-to-index ratios compared to controls.

## Abstract

Left atrial (LA) size and function are linked to exercise intolerance in heart failure, while associations between LA parameters and exercise performance remain unclear in athletes.

This study aimed to identify correlations between echocardiographic LA size, pressure, stiffness, and composite indices, and various exercise performance indicators.

Echocardiographic parameters were obtained from 181 physically active military personnel receiving regular training and tests for a 3-km run and 2 min of push-ups and sit-ups. The top 16% of runners were compared sex-specifically, with the remaining 84% as controls to identify LA discriminators for running capacity. LA composite indices were defined as the LA volume index (LAVI) divided by the stiffness index (LASI) or pressure index (mitral E/e′). Spearman correlations were used to identify LA correlates with exercise performance. Generalized linear regressions were used to identify LA predictors of exercise performance with adjustments for potential covariates.

The top 16% of runners vs. controls had a lower LASI based on LA volume changes (LASI_v, 0.196 vs. 0.245, p = 0.013) and higher LAVI-to-LASI_v (12.30 vs. 8.08, p = 0.001) and LAVI-to-(mitral E/e′) (4.37 vs. 3.76, p = 0.038) ratios. The LAVI-to-LASI_v ratio was the most highly correlated shared LA parameter for running (|rho| = 0.403), push-up (rho = 0.335), and sit-up (rho = 0.352) performance. The LAVI-to-mitral E/e′ ratio was the most highly correlated, independent, and unique LA parameter for running (|rho| = 0.457) performance.

The LAVI-to-LASI_v ratio, comprising LA size and stiffness information, was the best correlate across exercise types, while the LAVI-to-mitral E/e′ ratio, comprising LA size and pressure information, was the best correlate of an endurance exercise, i.e., 3-km running performance.