The physiological consequences of acceleration during shuttle running.

Area of Science:

• Sports Science
• Exercise Physiology
• Biomechanics

Background:

• Changing direction is a key component of many sports, particularly football.
• The physiological demands of acceleration during these changes are not fully understood.
• Quantifying training load often overlooks the specific demands of acceleration.

Purpose of the Study:

• To investigate the acceleration demands during changes of direction in football.
• To examine the physiological consequences of acceleration at various submaximal running speeds.
• To determine the relationship between acceleration frequency and physiological responses.

Main Methods:

• Ten male professional footballers performed 600m running bouts at 2.50, 3.25, and 4.00 m/s.
• Running formats included continuous laps and shuttle runs of varying distances (20m, 30m, 60m).
• Peak heart rate (HRPEAK), blood lactate (BLa), and rating of perceived exertion (RPE) were measured.

Main Results:

• Acceleration duration increased with running speed (1.2s at 2.50 m/s, 2.0s at 4.00 m/s).
• Increased time spent accelerating showed a linear correlation with elevated BLa (r=0.43-0.74) and RPE (r=0.81-0.93).
• Higher frequency of changes of direction led to a linear increase in acceleration demands.

Conclusions:

• Acceleration during changes of direction is a significant physiological stressor.
• Training load quantification in sports with frequent directional changes must account for acceleration.
• These findings emphasize the need to consider acceleration when designing training programs for footballers.