Improved infrared-sensing running wheel systems with an effective exercise activity indicator

Abstract

This paper describes an infrared-sensing running wheel (ISRW) system for the quantitative measurement of effective exercise activity in rats. The ISRW system provides superior exercise training compared with commercially available traditional animal running platforms. Four infrared (IR) light-emitting diode/detector pairs embedded around the rim of the wheel detect the rat's real-time position; the acrylic wheel has a diameter of 55 cm and a thickness of 15 cm, that is, it is larger and thicker than traditional exercise wheels, and it is equipped with a rubber track. The acrylic wheel hangs virtually frictionless, and a DC motor with an axially mounted rubber wheel, which has a diameter of 10 cm, drives the acrylic wheel from the outer edge. The system can automatically train rats to run persistently. The proposed system can determine effective exercise activity (EEA), with the IR sensors (which are connected to a conventional PC) recording the rat exercise behavior. A prototype of the system was verified by a hospital research group performing ischemic stroke experiments on rats by considering middle cerebral artery occlusion. The experimental data demonstrated that the proposed system provides greater neuroprotection in an animal stroke model compared with a conventional treadmill and a motorized running wheel for a given exercise intensity. The quantitative exercise effectiveness indicator showed a 92% correlation between an increase in the EEA and a decrease in the infarct volume. This indicator can be used as a noninvasive and objective reference in clinical animal exercise experiments.

Fig 1. ISRW system apparatus.

(a) Design drawing. (b) Actual photograph. The IR1–IR4 represents the locations of infrared sensing pairs.

Fig 2. Block diagram of the microcontroller-based control unit.

Fig 3. Construction of an adaptive exponential exercise acceleration training model.

The dotted lines represent the manual acceleration curves of 7 rats on Day 3. The solid line represents the automatic adaptive acceleration curve. The circle marker indicates the manual maximum operational deviation (14.4%).

Fig 4. Deployment of the IR sensors.

Fig 5. Flowchart of the main microcontroller program.

Fig 6. Flowchart of the three timer service routines of the microcontroller.

Fig 7. User interface on the PC (LabView program).

Fig 8. A 20-cm opaque piece of cardboard is used to verify the IR sensing accuracy.

Fig 9. Comparing the percentage of effective exercise activity in the ISRW (n = 9) and MRW (n = 9) groups.

(a) The average effective exercise activity each week. (b) The average effective exercise activity at three weeks.

Fig 10. Average mNSS, angle of the lower limb grip test and lesion volume in the five groups (9 rats each group) over a period of 7 days.

(a) The average mNSS at 7 days (mean ± SD). (b) The average inclined plane angle at 7 days (mean ± SD). (c) The average lesion volume based on reduced TTC staining (mean ± SD). The top panels of Fig 10(c) depicts a representative photograph of TTC staining for (A) a sham rat, (B) a control group rat, (C) a treadmill group rat, (D) a MRW group rat, and (E) an ISRW rat.

Fig 11. A comparison of the effective exercise activity results with the infarct volumes (Fig 9(b) was inverted and super-imposed on Fig 10(c)).