Is there a good formula to use for determining the training load to input as one of the fields?
Look at this site (http://fellrnr.com/wiki/TRIMP) for a formula for calculating training load if you do not have a Polar puls watch.
One tool for monitoring training load across different types of training (such as cardio, strength, and kickboxing), is the session-RPE method. Fortunately, it doesn't require extra equipment and is scientifically valid. Here is a link describing how it is done: http://www.ausport.gov.au/sportscoachmag/development_and_maturation2/monitoring_training_load
But the RPE function is already an option to fill in the daily notes function. I always fill inn the RPE scale and duration for my workouts.
The training load box is intentionally left open so that you can use any kind of measurement that you want. I like session-RPE because it spits out a number (session-RPE x Minutes= Training Load), so my strength workout yesterday was 7x64=448. If you find another training load measurement that you like, please re-post!