Progress of heart rate based training ~ Comparing result in 4 months ago

Doing a training plan in Garmin Connect!

I have been doing training regular basis for Marathon and hiking.   Unfortunately, I got injured in April and stopped training for 6 weeks this year.  Now, my fitness level is getting better after the injury.   I have done "Full Marathon - Level 1" in Garmin Connect from August till November and I started over the same menu December and this week is the third week.

Comparing the result on the same menu....

I compared two different training menu from the third week.  One is "threshold run" and the other is "long run".
Threshold run is warming up for ten minutes and 4 sets of high intensity (heart rate zone 4) for 4 minutes and resting for 20 seconds.
Long lone is 3 sets of brisk working for 10 minutes and slow jogging for 25 minutes.

Following tables are comparison of the results

 Comparison of threshold run

Lap	Time	December 13, 2017		August 23, 2017		Remark
		Distance	Average Pace	Distance	Average Pace
1	10:00	1.40	7:09	1.36	7:20	Warm-up
2	4:00	0.81	4:57	0.70	5:43	High intensity
3	0:20	0.04	8:07	0.04	9:06	Rest
4	4:00	0.75	5:19	0.74	5:24	High intensity
5	0:20	0.04	8:33	0.04	8:36	Rest
6	4:00	0.69	5:45	0.66	6:04	High intensity
7	0:20	0.03	10:49	0.03	12.50	Rest

Comparison of long run

	December 16, 2017	August 26, 2017
Distance	13.60	12.73
Total Time	1:48:19	1:46:08
Agerage Pace (min/km)	7:58	8:21

Those distributions of heart rate zones are very similar and they indicates I can run faster with a similar heart rate.  Now I am doing the same training plan and my pace is faster than the previous.  I expects to get more improvement with this menu.

This is a good thing for heart rate based training.

I just wonder if I need to step up to "level 2".  But it seems that the same menu (level 1) would be good for now.  Especially, it is better to stay and getting a small improvement without over training.