After seven months off, you will have lost a significant amount of fitness. How much is hard to say. It depends on your training history. If you’ve been training for decades, then it should come back fairly quickly (within months). If you’re relatively new to structured training, then it will take longer.

As for intensities, I would start with a drift test to determine your current aerobic threshold. Detraining tends to skew intensity toward the anaerobic side, so your AeT HR at the moment is likely lower than what it was.

Most importantly, don’t make the common mistake of trying to “cram”. You can’t speed up the process by upping the intensity or over-doing it on duration. That will only set you back further. If you’re patient and progressive with it, you’ll get the best results you can.

If 150 was previously AeT, then training in the 130s seems reasonable for now.

Before spending money on a lab test, I would get in at least a month of solid training. After a long lay off, things tend to become more anaerobic and so you may have higher heart rates for a given intensity than you will after a month of easy volume.

For example, I’ve been out for three weeks with a bad sinus infection. I just went out today and put in an hour at a pretty easy pace. Based on my speed in a known section of trail, my heart rate was ten beats higher than normal. So if I did any kind of threshold test right now, the results wouldn’t be very helpful. The shelf life of the information would be too short.