Ocular Accommodative Response is Modulated as a Function of Physical Exercise Intensity

Area of Science:

• Exercise physiology
• Ocular physiology
• Autonomic nervous system function

Background:

• Dynamic accommodative response (AR) is crucial for clear vision during tasks requiring focus adjustment.
• Heart rate variability (HRV) reflects autonomic nervous system activity and is influenced by exercise intensity.
• Understanding the interplay between exercise and visual function is important for athletes and individuals performing near work post-exercise.

Purpose of the Study:

• To investigate the impact of two high-intensity interval training (HIIT) protocols, differing in intensity, on dynamic accommodative response (AR).
• To determine if changes in ocular accommodation are associated with autonomic nervous system function, assessed via HRV, during stimulus processing.

Main Methods:

• Twenty physically active university students participated in three randomized sessions: low-intensity HIIT, high-intensity HIIT, and a control condition.
• Measurements included accommodative lag and HRV (specifically, the root mean square of successive R-R interval differences [RMSSD]) at the beginning and end of each session.
• HIIT protocols involved 8 sprints with varying rest periods (60s for low-intensity, 30s for high-intensity), while the control involved 8 minutes of walking.

Main Results:

• High-intensity HIIT resulted in a significantly greater accommodative lag compared to both low-intensity HIIT and the control condition.
• No significant differences in accommodative lag were found between low-intensity HIIT and the control condition.
• While higher exercise intensity led to lower HRV values, AR changes and HRV were not significantly correlated.

Conclusions:

• The acute effects of exercise on ocular accommodation are intensity-dependent.
• Highly demanding physical exertion, such as high-intensity HIIT, can induce a more pronounced accommodative lag.
• This increased accommodative lag may have practical implications for individuals engaged in near-vision tasks following strenuous physical activity.