Arterial flow waveforms, vascular tone, and chronic fatigue: a case report

Photoplethysmography Detection of Overreaching

INTRODUCTION

Detecting the onset of functional overreaching (FOR) or nonfunctional overreaching in endurance athletes is of prior importance to ensure reactive amendment of the scheduled training program. The objective of this study was to assess photoplethysmography (PPG) in overloaded athletes and test whether 1) it would be affected differently in functional overreached (FOR) or nonoverreached acutely fatigued (AF) athletes and 2) specific PPG characteristics would allow for timely distinction of FOR and AF.

METHODS

Fifteen athletes performed 2-wk baseline training followed by 3-wk overload (+45%; OVL) and 2-wk recovery (-20%). Three-thousand-meter time-trial running was used to assess performance at the end of baseline, OVL, and recovery and distinguish FOR and AF. PPG was recorded overnight using a wearable sensor, every third night. Overnight means and variances of systolic, diastolic, and dicrotic amplitudes and times as well as systolic and diastolic slopes were used to discriminate FOR and AF athletes.

RESULTS

Performance was decreased in FOR and improved in AF at the end of OVL. Diastolic time was greater in AF than FOR, whereas systolic slope was smaller in AF than in FOR during OVL. The variances of systolic, diastolic, dicrotic amplitudes, systolic, diastolic slopes, and pulse areas were smaller in AF compared with FOR in the last week of OVL.

CONCLUSION

PPG is an efficient tool for the detection of overreaching because it distinguished FOR and AF athletes during OVL (prior performance decrement). This fast-responding method would therefore allow for adjusting the daily training content to prevent nonfunctional overreaching.

The dicrotic notch analyzed by a numerical model

Divergent concepts on the origin of the dicrotic notch are widespread in medical literature and education. Since most medical textbooks explain the origin of the dicrotic notch as caused by the aortic valve closure itself, this is commonly transmitted in medical physiology courses. We present clinical data and numerical simulations to demonstrate that reflected pressure waves could participate as one of the causes of the dicrotic notch. Our experimental data from continuous arterial pressure measurements from adult patients undergoing vascular surgery suggest that isolated changes in peripheral vascular resistance using an intravenous bolus of phenylephrine (a selective alpha 1-receptor agonist and thus a potent vasoconstrictor) modify the dicrotic notch. We then explore the mechanisms behind this phenomenon by using a numerical model based on integrated axisymmetric Navier-Stokes equations to compute the hemodynamic flow. Our model illustrates clearly how modifications in peripheral artery resistance may result in changes in the amplitude of the dicrotic notch by modifying reflected pressure waves. We believe that this could be a useful tool in teaching medical physiology courses.