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Table 3 Summary of the SM dose-physiological response relationship in animal studies

From: Spinal manipulation frequency and dosage effects on clinical and physiological outcomes: a scoping review

Studies Dosage parameters Sample size Spine level Muscle spindle activity - main results
[30] Cao et al., 2013 Thrust forces: 25, 55, 85% of BW n = 112 cats L6 Consistent increase in MIF for 1 mm thrust amplitude.
Thrust displacements: 1, 2 or 3 mm No specific trend associated to modulation in forces and displacements
Thrust durations: 0,25,50,75,100,150,200, 250 ms
[35] Pickar et al., 2006 Thrust forces: 33, 66, 100% of BW n = 46 cats L6 Data suggest that decreasing thrust duration increases ΔMIF
Thrust duration: 25, 50, 100, 200, 400 or 800 ms There is a threshold effect for duration for which the discharge greatly increases
[36] Pickar et al., 2007 Thrust displacement: 1 or 2 mm n = 54 cats L6 Data suggest that decreasing thrust duration increases ΔMIF
Thrust duration: 12.5, 25, 50, 100, 200, 400 ms
Peak thrust amplitude (1 mm compared to 2 mm) influence ΔMIF
[37] Reed et al., 2013 Thrust forces: 25, 55, 85% of BW n = 112 cats L6 Data suggest that decreasing thrust duration increases mean spindle discharge through range of forces.
Thrust displacement: 1, 2 or 3 mm Through a range of force durations, increasing force seems to increase ΔMIF.
Thrust durations: 25, 50, 75, 100, 200, 250 ms For most thrust duration, peak thrust displacement did not influence ΔMIF.
Increasing force rates increased MIF
[38] Reed et al., 2015 Thrust force: ranges from 68 N to 122 N n = 1 cat L7 Data suggest that increasing force leads to increase ΔMIF.
[39] Reed et al., 2014 Preload variation: 18% or 43% of thrust force n = 20 cats L6 Increasing longer preload duration (4 s compared to 1 s) increases ΔMIF.
Thrust durations: 1 or 4 s (Thrust force: 55% of BW)
A smaller magnitude of preload (18% compared to 43%) increases ΔMIF
The highest preload magnitude and longest duration led to a significantly greater mean decrease in resting spindle discharge
[40] Reed et al., 2017 Thrust force: 22 N, 44 N or 67 N n = 6 cats L6 Data suggest that increase in force increased the time required until the first action potential.
  1. MIF Mean Instantaneous Frequency, ΔMIF Changes in Mean Instantaneous Frequency, BW body of weight