Documentation

Introduction

The Treadmill Harness is used to weight support rodents during Treadmill training. Bodyweight support (BWS) systems are a popular rehabilitation approach to gait training in humans (Sousa, Barela, Prado-Medeiros, Salvini, & Barela, 2009; Matsuno, Camargo, Palma, Alveno, & Barela, 2010). Rodent models of diseases and disorders that lead to mobility deficits utilize the Treadmill Harness during Treadmill training to help understand the effects and improve the application of BWS systems in human mobility reestablishment programs.

The Treadmill Harness is composed of a harness and body weight support mechanism. The animals are fastened into the harness, which consists of a Velcro strap vest having two holes for the limbs. Additional straps are attached at the end opposite the holes, to allow bipedal training. The harness is then attached to the bodyweight support mechanism at both rostral and caudal ends. The weight supported during the Treadmill training is determined by adjusting the weight support springs. The body weight support mechanism fixes the subject to a position on the treadmill while training.

The Treadmill Harness, in addition to mobility training, is also useful in analyzing the benefits of exercise in improving sexual health and sensory deficits that arise from spinal injuries (Hubscher et al., 2016). The harness can also be used in aiding animals in other training protocols. Other apparatuses that are used for the assessment of motor and locomotion functions include the Rotarod, the Grid Test, the Gait Test, and the Parallel Rod Test. (For more motor assessment apparatuses, click here.)   

Apparatus & Equipment

The Treadmill Harness is composed of two parts: harness and body weight support mechanism. The harness is made of a fabric designed as a vest with Velcro straps to fit the animal snuggly. Additional straps are attached to the end of the vest that creates a hook-and-loop mechanism to lift the hind limbs of the animal when attached to the weight support mechanism.

The body weight support mechanism is constructed using adjustable metal clamp systems. Alligator clips attached to the ends of weight support springs are used to attach the harness to the system and support the animal’s weight. The springs can be adjusted to control the weight support the animal receives.

Training Protocol

When using a Treadmill Harness for training protocols, ensure that the harness and the bodyweight support mechanism are cleaned prior to use to prevent any lingering stimuli from influencing the subject performance. Choose an appropriately sized Treadmill Harness that fits the animal snuggly and does not cause any undue discomfort. 

Adjust the weight support springs according to the protocol needs and attach the alligator clips at rostral and caudal ends of the harness vest.

The following is a sample protocol for treadmill training that utilizes the Treadmill Harness in spinal cord injury rodent model. Protocols will vary depending on the aim of the investigation and the training apparatus.

Activity-based Training (ABT) on Treadmill

Ensure that the apparatus is appropriately lit, and the task is performed in an undisturbed environment to minimize the influence of any external stimuli on the performance. Tracking and recording of the performances can be done with the assistance of an external tracking and video system such as the Noldus EthoVision XT.

Pre-training

Prior to introducing the animal to the treadmill harness and the training protocol, handle the animals for 5 to 10 minutes daily, for at least one week to familiarize them with the experimenter. Follow this by subjecting the animal to the spinal cord injury protocol and allow it to recover for at least two weeks.

Training

Begin training by first allowing the animals to acclimate to the treadmill and the treadmill harness. Place the subject in the harness and attach it to the bodyweight support mechanism adjusted to the requirement of the training protocol applied. Initially, begin training the subjects at a slow speed for 10 minutes. Gradually increase the speed and the time spent on the target values as the days progress.

Following acclimation, begin training the animals on the Treadmill training while maintaining their weight support conditions.

Literature Review/ Scientific Research

Investigation of the effects of ABT on urinary functions following SCI

Gumbel, Montgomery, Yang, and Hubscher (2020) investigated the potential effects of activity-based training (ABT) on SCI-induced polyuria. Fort adult male Wistar rats were divided into SCI and SHAM surgery groups. The SCI group underwent a T8/T9 laminectomy to expose the T8 spinal level and received a moderate-severe contusion (225 kilodyne; no dwell time). The SHAM group underwent laminectomy without the administration of contusion injury. Following a two weeks recovery period, SCI animals were divided into non-trained control (SCI+NT), non-trained home cage control (SCI+HC), quadrupedal trained (SCI+QT), and forelimb-only trained (SCI+FT). The SCI+QT and SCI+FT groups were placed in treadmill harnesses and trained on the treadmill at 10 minutes increments for 5 days until they reached the 1-hour target time. The forelimb-only trained (SCI+FT) had the additional straps on the vest tied around them to lift the hind limbs such that no weight was applied on them, and they did not touch the treadmill. The SCI+NT group was also placed on a harness and kept on a stationary surface. Following the acclimation, the subjects underwent 8 weeks of Treadmill training. The SCI animals that underwent ABT had reduced urine volume (14.7 mL) at the end of the training regime in comparison to the non-trained group (21.2 mL). Relative to the pre-SCI baseline levels, ABT groups showed a 58.2% decrease in serum arginine vasopressin levels. However, ABT had no significant effect on atrial natriuretic peptide levels.

Investigation of the effects of ABT on sexual health following SCI

Steadman, Hoey, Montgomery, and Hubscher (2019) investigated penile reflex response in SCI rats following ABT. Adult male Wistar rats received a 215-kilodyne contusion injury following the removal of T8 lamina to expose the T9 cord. A SHAM group underwent the SCI procedure without the contusion injury. The SCI groups were them divided into non-trained control (SCI+NT), non-trained home cage control (SCI+HC), quadrupedal trained (SCI+QT), and forelimb-only trained (SCI+FT) following 2 weeks recovery. The ABT groups were placed in the harness and underwent 8 weeks of 60 minutes of treadmill training. Animals initially started at a warm-up speed, which was increased to an adaptability speed. In the first 30 minutes the animals spent at the adaptability speed, the non-trained control was also harnessed but placed on a stationary surface. The SCI+QT group displayed a significantly increased latency to penile dorsiflexion reflex onset in comparison to the SCI+FT group at weeks 4 and 8 of ABT. The trained groups also showed a significantly shorter burst duration as measured during the bulbospongiosus EMG. Additionally, the SCI+QT group had significantly decreased bulbospongiosus latency onset in comparison to the SCI control groups.

Strengths and Limitations 

Strengths

The sucrose preference test offers a simple two-choice design. The tasks in the sucrose preference test apparatus rely on the rodents’ natural preference for sweet food. Each chamber is equipped with two tube holders for holding the sucrose solution and regular water. Therefore, the fluid intake can be easily assessed. Any leakages are determined by placing tissue paper pads in the chambers.

Limitations

Experimental variables such as dietary influences, use of different mouse strains, environmental inconsistencies, and differences in animal handling may affect the results. Weight variance in subjects also affects the absolute intake value of sucrose solution.

Summary

• The Treadmill Harness is used as a bodyweight support system for rodent training.
• The Treadmill Harness is composed of a harness vest and a bodyweight support mechanism composed of weight support springs and clamp set-up.
• The harness vest must be selected to provide a snug fit. Incorrect sizing may affect the support provided or cause the subject undue stress.
• The body weight support mechanism fixes the subject’s position on the treadmill.
• The application of the Treadmill Harness can be extended to other behavioral assays.

References

1. Gumbel, J. H., Steadman, C. J., Hoey, R. F., Armstrong, J. E., Fell, J. D., Yang, C. B., … Hubscher, C. H. (2019). Activity-based Training on a Treadmill with Spinal Cord Injured Wistar Rats. Journal of Visualized Experiments, (143). doi:10.3791/58983
2. Sousa, C. O., Barela, J. A., Prado-Medeiros, C. L., Salvini, T. F., & Barela, A. M. (2009). The use of body weight support on ground level: an alternative strategy for gait training of individuals with stroke. Journal of NeuroEngineering and Rehabilitation, 6(1), 43.
3. Matsuno, V. M., Camargo, M. R., Palma, G. C., Alveno, D., & Barela, A. M. F. (2010). Analysis of partial body weight support during treadmill and overground walking of children with cerebral palsy. Brazilian Journal of Physical Therapy, 14(5), 404-410.
4. Gumbel, J. H., Montgomery, L. R., Yang, C. B., & Hubscher, C. H. (2020). Activity-Based Training Reverses Spinal Cord Injury-Induced Changes in Kidney Receptor Densities and Membrane Proteins. Journal of Neurotrauma, 37(3), 555-563.
5. Steadman, C. J., Hoey, R. F., Montgomery, L. R., & Hubscher, C. H. (2019). Activity-based training alters penile reflex responses in a rat model of spinal cord injury. The journal of sexual medicine, 16(8), 1143-1154.
6. Hubscher, C. H., Montgomery, L. R., Fell, J. D., Armstrong, J. E., Poudyal, P., Herrity, A. N., & Harkema, S. J. (2016). Effects of exercise training on urinary tract function after spinal cord injury. American Journal of Physiology-Renal Physiology, 310(11), F1258-F1268.