Mechanical work and efficiency of 5 + 5 m shuttle running

Area of Science:

• Biomechanics
• Exercise Physiology
• Sports Science

Background:

• Shuttle running (SR) involves distinct acceleration and deceleration phases, unlike constant speed running (CR).
• This difference suggests higher mechanical work requirements in SR compared to CR at equivalent average speeds.

Purpose of the Study:

• To quantify total mechanical work (W tot (+)) in shuttle running, comprising internal (W int (+)) and external (W ext (+)) work.
• To determine the mechanical efficiency of shuttle running.

Main Methods:

• Twenty male participants performed shuttle runs over 5m + 5m at varying speeds (slow, moderate, fast).
• Kinematic data were recorded for all speeds; metabolic data were collected at fast speeds.
• Energy cost (C) and mechanical efficiency (eff(+)) were calculated using recorded data.

Main Results:

• Work parameters (W ext (+), W int (+), W tot (+)) significantly increased with mean velocity (v mean).
• At the fastest speed, energy cost (C) was approximately 7 times higher than in CR (27.4 ± 2.6 J kg⁻¹ m⁻¹).
• Mechanical efficiency (eff(+)) was measured at 16.2 ± 2.0%.

Conclusions:

• External work (W ext (+)) is greater in SR than CR, and internal work (W int (+)) constitutes a significant portion of total work.
• Mechanical efficiency (eff(+)) is substantially lower in SR (16%) compared to CR (50-60%).
• Reduced elastic energy reutilization during the acceleration/deceleration cycles in short shuttle distances likely accounts for the lower efficiency in SR.