Table 3.  Evidence for Motor Unit Firing Frequency.
Author
Participants
Vibration Method (type)
Exercise Type
Frequency  (Hz)
  Amplitude
(mm)
Duration
Results
Bongiovanni and Hagbarth, 1990
5 H
(
, = NR)
Direct vibration dorsiflexor muscles
SS
150
1.5
20-25 s
Vibration had no effect on firing frequency of non-fatiguing muscle, however vibration caused an increase in EMG, force and firing frequency during fatiguing isometric maximal voluntary contractions.
Griffin et al., 2001
7 H (3, 4)
Direct Vibration triceps & biceps brachii
Isometric
110
3
2 s
every 10 s
The firing frequency of the triceps significantly increased when vibration was applied during 20% MVC
H = Healthy; SS = Static squat; MVC = Maximal voluntary contraction