Below is a rough way to interpret those 300 m repeats and arrive at a ballpark 5 km fitness. Obviously, “conversion” from an interval workout to a race performance is never exact (due to rest intervals, individual strengths/weaknesses, etc.), but here’s the general reasoning:
1. Looking at the Average Paces
• Set 1 (15×300): ~51.7 s average
• Set 2 (10×300): ~50.9 s average
• Set 3 (5×300): Ranging 47.3–49.7 s
If you convert 51–52 s for 300 m directly into a 5 k pace without rest, you end up around 14:20–14:30 for 5 km. However, that’s an overestimate of actual 5 k race pace because you are getting:
1. Short 100 m jogs between reps.
2. A full 5 minutes rest between sets.
Still, the sheer volume of 300s (30 total, which is 9 km of quality work) at ~51–52 s, then speeding up in the last set, suggests you’re running these at (or slightly faster than) 5 k effort.
2. Considering the Altitude (4000 ft)
A common rule of thumb is that performance can slow by roughly 1.5–2.5% for races in the 3000–5000 ft range (it varies by individual). For a 5 k in the 15:00 range, that can mean easily a 15–25 second difference between sea level and 4000 ft.
3. Putting It All Together
• Hitting 15–25 reps of 300 m around 51–52 seconds with only 100 m jog implies you are likely in the low- to mid-15:00 shape (at altitude).
• The fact you not only maintained that but sped up in the last set (with reps dipping under 50 s) points toward sub-15:00 fitness at sea level, quite possibly in the 14:40–14:50 range.
• Adjusted for 4000 ft, you might be capable of something around 15:00–15:10 on the same day if you actually raced a 5 k at altitude.
In short: You are very likely in sub-15:00 5 k shape at sea level, somewhere around 14:45–15:00 (give or take), with an additional 10–30 seconds added if you raced at 4000 ft depending on how well you handle altitude.