The Beurer unit is probably not ideal. But it delivers both near and medium range IR. I didnt want to spend much testing the concept since I had nothing but this article to go on.
But it worked unbelievably well. As for worries of too much heat you're fine if you follow the advise of the Beurer instructions.
1) keep the lamp 12-16 inches away. Personally if I feel anything more than comfortable warmth I'll move it back till it's fully comfortable. Usually 14-16 inches away. And
2) stop each session after no longer than 20 minutes which the article itself also recommends. The Beurer automatically powers down after 15 minutes anyway.
I thought about going for a low power near IR only LED if I got any improvement alt all using this. But it does the job so well there's no need to bother at this point.
Actually the slight heat on the lower to mid back feels good and helps with sleep as a bonus.