Research - Validation Studies
Effects of fatiguing loading with a variable resistance equipment on neural activation and force production of the knee extensor muscles.
Year: 1988 Country: Finland Study Population: N=7 strength athletes
Häkkinen K, Kauhanen H, Komi PV. Effects of fatiguing loading with a variable resistance equipment on neural activation and force production of the knee extensor muscles. Electromyogr Clin Neurophysiol. 1988;28(2-3):79-87.
A follow-up study to examine the effects of fatiguing loading with variable resistance equipment on neural activation and force characteristics of the knee extensor muscles.
Muscle activation (measured as EMG) and maximal isometric force of the knee extensors were measured. After this the participants trained with 60 % concentric loading with a variable resistance device (David 200) after which the maximal voluntary isometric measurements were repeated immediately and after 3 minutes of recovery period.
The training effects were compared to the data obtained during a corresponding loading with a normal constant resistance device.
Significantly more repetitions were needed to cause fatigue against the 60% constant resistance than in the corresponding fatigue loading against the variable resistance device. The fatigue loading against the variable resistance resulted in a great decrease in maximal isometric force which did not recover during the following 3 minutes.
The fatigue loading against the constant resistance was associated by a decrease in the knee angle of the full extension phase. During the final phases of the fatigue the activation of the muscles was the same for all knee angles in the loading with the David device whereas in the loading against the constant resistance, the average activation of the muscles decreased for the final knee angular phases of the extension.
The results indicate that the repeated concentric contractions of the knee extensor muscles against the variable resistance may create optimal resistance loading conditions that result in great fatiguing effects on the neuromuscular performance.