TheStack App

TheStack App provides customized variable inertia speed training - the most efficient way to increase your clubhead speed. The algorithms that power the dynamic programming come from years of research by leading sports scientist, Dr. Sasho MacKenzie.  TheStack App is available on iOS only and requires iOS 15.0 or later.

Watch Co-Founder Marty Jertson describe what goes into TheStack App.


Here are more details on how the App works

Dynamic Training Programs

TheStack App functions as your own personal trainer, guiding you through scheduled workouts while tracking Stack weight, rest, recovery, and performance gains. This information allows future workouts to be adjusted behind the scenes, so your training is optimized to maximize clubhead speed gains.

Baseline Session

Similar to working with a personal trainer, you are guided through a detailed intake session. Qualitative data is gathered on perceived strengths and weakness related to generating clubhead speed. You'll be coached through a series of swing speed tests to generate a force-velocity profile of your current swing. This data informs A.I. algorithms which create custom programming options. 


Following the Baseline Session, TheStack App provides a list of customized programming options. The list is prioritized specifically for you by greatest likelihood of increasing clubhead speed over a 6 to 10 week period (18 to 24 training sessions).


During each training Session, TheStack App coaches you through each swing - seamlessly guiding stack weight configuration, swing intent and rest for each rep and set.

Hands-Free Data Collection

Using TheStack System’s voice entry technology, enjoy hands-free data collection during training sessions, by simply dictating your speed readings into the App. The hands-free data capture feature even works when wearing AirPods or earbuds. If you are training with a coach or friend, numbers can be keyed.


Workout Summaries

Detailed post-workout data review enables you to verify and, if needed, make any changes to speed data before syncing to the cloud.

workout summary

Tracking and Sharing Metrics

TheStack App tracks key performance metrics such as Stack Speed, Distance Potential, Clubhead Speed and Grit Score. Easily share your progress and gains to your favorite social media platform.


Progress Checks

After completing a training program, TheStack App re-assesses your gains with a Progress Check, from there reformulating your next program. Data captured along the way improves the intelligence of TheStack algorithms through A.I. techniques.     

progress check

Cloud Storage

Training data is stored securely in the cloud.  Whether you get a new phone or want to login from another device for your next training session, everything works seamlessly.

Junior Stack Training

Kids 10+ can benefit from training with The Stack System.  If your child is 13 years old or younger, they must train as a Local Golfer under their parent or guardian’s profile in TheStack App.



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