Isokinetic Exercise Machine Using High Performance MR Fluid Brake and Iso-Contraction Exercise - Biomechatronics in Medicine and Healthcare - page 161

150

40

Subject A

100

20

Subject B

50

Subject C

0

0

0 400 800

Angular Velocity (deg/s)

Figure 11.12 Experimental results for subject B.

results for subject A, white circles for subject B, and double circles for subject C.
Solid lines indicate Hill's curves and broken lines power curves. In obtaining
Hill's curves, parameters a and b in Eq.(1) , where P denotes operation torque [Nm]
and V exercise velocity [deg/s], were determined by applying the least squares
method. In obtaining power curves, the product of P and V was converted to watts
(W). The power curve peak represents the speed and power at which the subject
exercises most efficiently: 139 W (700 deg/s) for subject A, 93 W (525 deg/s) for
subject B, and 43 W (375 deg/s) for subject C. References (Fuchimoto, 1981) report
141 W as the maximum power developed in elbow flexion by 19-year-old men, so
experimental results appear to be valid.
Isokinetic exercises thus enable muscles of subjects to be evaluated from
different points, including maximum muscle power, maximum exercise efficiency,
and speed in most efficient exercise.

11.5 ISO-CONTRACTION EXERCISE

11.5.1 Control Method

As discussed in Section 4.1, unlike in isokinetic exercises, input command speed
ω re f is not constant but changes with the angle, and dL/dt in Eq. (11.3) becomes
constant. Fig. 11.13 shows examples of reference angular velocity curves (control
input): angles in Eq. (11.2) are plotted on the horizontal axis, and angular velocity
on the vertical axis. To draw up these reference curves, we must determine R and
r in Eq.(11.3) . In fact, however, it is difficult to determine actual in vivo R and r .
These values are determined in relation to subject height H [m].
Based on references, we set the average bicep length at 0.18 times subject
height (Kouchi, 2000). The origin biceps brachii muscle, attached to the shoulder
blade and a bit shorter than the biceps, is determined as follows:

R = 0.18 × 0.95 × H (11.7)