How is training load calculated?

Hi all

Here a simple example and simple values to show where my confusion comes from:

Training 1, 44:38 running, 5:18 pace, average 141 bpm HR (all in zones 2 and 3), 724 calories = training load 203

Training 2, 1:00:16 indoor cycling, average 146 bpm HR (mucho more zone 3 than previous and 5% at zone 4), 869 calories = training load 162

Looking at the training effect, I got 4.2 and 3.8, respectively.

Does anyone know the reason for this? If the heart rate is higher even for different exercises, shouldn't the training load be higher too?

Thank you so much!!