Short session (≤10 min) high intensity interval training (HIIT) is emerging as an alternative to longer exercise modalities, yet the shorter variants are rarely modeled in animal studies. Here, we describe a 10 min, 3 day a week, uphill treadmill HIIT protocol that enhances physical performance in male and female aged mice.
Our goal has been to enhance health span as we age. Even in the face of disease. High intensity interval training, or HIIT, increasingly shows great promise to deliver performance gains.
The main advantage of this technique is that significant gains in performance are generated with short sessions administered several times a week. This framework explores the impact of high intensity interval training on aging. With aging, there's increased variability in physical performance.
A key aspect of our method is that the protocol intensity can be individually tailored. An important goal of this research is develop or modify human short session HIIT protocols. That's providing a template for clinical studies.
Demonstrating the procedure will be Yonas Redae, a research associate from our laboratory. In this procedure, 24 female mice on a C57-BL6J background were observed starting at 23 months of age. Ensure that mice receive permanent identifiers such as ear tags, RFID chips, or tail tattoos.
Clean the treadmill with 0.25 to 0.5%bleach, or 70%ethanol at the end of the day. Or to remove feces or urine between experimental trails. Dry the treadmill completely, before initiating a new trial.
Set up the initial training program using the treadmill software in manual mode. Open the treadmill software. Then click on the file, open the experiment, and navigate to the manual tab.
There, input the values indicated in table one under acclimation. Input the session number as one. The number of active channels is between one and six depending on the number of mice.
The number of visits to the grid is 10. And the number of shocks is 20. Set the inclination of the treadmill to zero degrees.
Hold mice by the tail when placing in the treadmill. And place mice directly on the belt to avoid starting mice on the shock grid. Use a brush or tongue depressor to keep mice away from the shock grid when training or assessment begins.
Nudge mice to begin running to avoid unintended shocks. After each mouse is given the initial training program, repeat the program as before. With the shock intensity increased to level two and at least 15 minutes between trainings.
Administer the uphill treadmill acclimatization one to two days after the initial training program. Open the treadmill software. Then click on the file and open the experiment.
Input the values on the basic tab. Under shock detection, input the session number as one. The number of active channels is between one and six depending on the number of mice.
The number of visits to the grid is 10. And the number of shocks as 20. Now, click on the profile mode tab, and for step one input a start speed of zero meters per minute and an end speed of five meters per minute with a period of five seconds.
Add a warm-up step two with a start speed of five meters per minute, and an end speed of five meters per minute for 30 seconds. Add a transition step that starts at five meters per minute and ends at six meters per minute for five seconds. Then add a test speed step that starts at six meters per minute, and ends at six meters per minute, for 20 seconds.
Add a transition step that starts at six meters per minute, and ends at five meters per minute. Finally, add a recovery interval that starts at five meters per minute, and ends at five meters per minute for 20 seconds. Repeat these steps to add test steps as indicated in table two under acclimation.
For flat continuous treadmill assessment, create a treadmill program as before using the values indicated in table one under assessment. Monitor the mice throughout the trial and remove mice from the instrument that reach the end point criteria. For uphill interval treadmill assessment, create the treadmill program as before using the values indicated in table two under assessment.
Under shock detection, set the session number as one. The number of active channels as one and six depending on the number of mice. The number of visits to the grid as five and the number of shocks as 10.
Set the interval field in the treadmill program to 0.5. To perform a short session of high intensity interval training, first set the treadmill uphill at 25 degrees and remove the plastic cover. Determine the intensity for each mouse.
Use the speed of the last successfully completed stage and find the intensity group and corresponding base, sprint, and dash. Open the treadmill software, and click on file to create a new program. Click on the profile mode tab.
For step one, input a start speed of zero meters per minute, and an end speed equal to the corresponding base speed with a period of five seconds. Add a warm-up step two, with a start speed at base speed, and an end speed at base speed, for 180 seconds. Now, input three intervals, each with a transition step that goes from base to sprint for five seconds.
A step at sprint speed for 60 seconds. A transition step that goes from sprint to base over five seconds. And a step for a recovery interval at base speed for 60 seconds.
Add a transition step that goes from base to sprint speed over five seconds. And a final step that goes from sprint to dash speed over 60 seconds. Perform exercise three days a week with at least one day of rest between sessions.
Rewrite exercise programs to increase base, sprint, and dash speeds, one meter per minute every two weeks. Motivate mice to run using a make-up brush, or tongue depressor to lightly encourage mice that fall near or on the shock grid. If a mouse does not respond, retry in five seconds, then 10 seconds, and then retry every 30 seconds, or during a recovery interval until the end of the session.
Applying motivation can be difficult with multiple mice. Two brush may be necessary. Additionally the administrator must identify mice that struggle or excel to appropriately adjust the testing.
Move mice that cannot be motivated to complete the first three intervals in two consecutive exercise sessions to lower intensity groups. Move mice that do not require motivation in two consecutive exercise sessions to higher intensity groups. At 24 months of age, mice were accessed for treadmill endurance.
And uphill sprint capacity prior to and after the administration of two months of HIIT exercise or remaining cage sedentary. The data show that all 14 mice in the HIIT group increased treadmill time on the belt as compared to seven of 11 of the sedentary mice. In total, HIIT mice exhibit a greater improvement in time on the belt based on the better of two trials.
Additionally, a greater increase was detected in uphill treadmill capacity as 12 of 14 HIIT mice increased maximal speed while there was a decline in eight of 11 sedentary mice. HIIT mice also demonstrated greater improvement in maximal speed compared to sedentary mice, based on the better of two trials. Shock tolerance was similar between the two groups of mice.
Remember to rewrite the HIIT programs to increase intensity every two weeks. Program files can be copied and modified to make these steps easier. Additionally, this method would be strengthen by including anerobic parameters such as glycolytic metabolism, phosphocreatine utilization, and lactate kinetics, which quires how exercise effects aerobic and anerobic respiration.
