HR lag and hitting HR targets on a treadmill | 80/20 Endurance

HR lag and hitting HR targets on a treadmill

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  • #9543

    Hi all, just starting out on a 80:20 70.3 plan and today I did my first (for this plan) run workout on a treadmill. My plan is HR based for running so today I was simply trying to hit my targets as close a possible.

    Last week I did a lactate test in a lab and the output from that was a graph showing my speed (on the labs very expensive treadmill) vs my heart rate.

    The treadmill I have access to doesnt have custom workouts so today I was trying to do 10 x 1min (with 2 mins z1 after each) at around 160bpm. In order to get to that target for each interval I set the speed to the same speed as I was running at when I hit 160 in the lab. Thats when I realized HR lag is an issue.

    The lab results told me I should hit 160 at 11.3 km/h, so I set the speed at that. My HR was nowhere near 160.. so I upped the speed to 12, 13, 14.. and still it didnt hit 160.

    So I started thinking.. when I did the lab test id already been running for 25 mins when I hit 160.. so my HR had chance to climb as the lab test progressed. Today the workout had a 20min z2 segment and then we hit the intervals.. so the HR didnt have chance to climb like in the lab.

    I read something online today that said dont overcompensate when trying to get your HR up for intervals.. stick to the speed from your lab/outdoor lactate test.. but I needed to hit 160 today 10 times in order to complete the workout correctly. So I wondered if anyone had a view on this.. Should you do whatever you can to get your HR to the desired target even if that means going too fast for part of the interval to get the HR up.

    I did the same today when I came off the hard intervals.. I reduced the speed right down to 7.3 to get my HR back to the target of 120. But 7.3 is super slow.. I even walked some of the 2 min rests at 7.3.. but it had the desired effect and got the HR back to 120.

    Any thoughts welcome.

    Thanks

    #9545
    alancraig
    Participant

    When you’re doing intervals, I would just stick with the appropriate effort. Otherwise, you’ll end up pushing too hard during the fast intervals and backing off too much during the recovery periods. Even if you’re doing the rest of your training by heart rate, I would either go by pace or perceived effort for intervals.

    Here’s a great quote from the 80/20 book that addresses the issue:

    “Heart rate monitoring is less useful in high-intensity runs. The reason has to do with a phenomenon called cardiac lag. When you speed up during a run, your heart will respond by increasing its contraction rate until it is sufficient to supply your muscles with the extra oxygen they’re now asking for. This process is not instantaneous. Depending on how much your pace increases, it may take your heart thirty seconds or more to settle into a new rhythm. Cardiac lag has important implications for heart rate monitoring. Heart rate monitoring is less useful in high-intensity runs. The reason has to do with a phenomenon called cardiac lag. When you speed up during a run, your heart will respond by increasing its contraction rate until it is sufficient to supply your muscles with the extra oxygen they’re now asking for. This process is not instantaneous. Depending on how much your pace increases, it may take your heart thirty seconds or more to settle into a new rhythm. Cardiac lag has important implications for heart rate monitoring.”

    I hope this helps!

    #9549
    alancraig
    Participant

    Sorry, I just realized that I copied and pasted the same thing twice. Here is the full quote:

    “Heart rate monitoring is less useful in high-intensity runs. The reason has to do with a phenomenon called cardiac lag. When you speed up during a run, your heart will respond by increasing its contraction rate until it is sufficient to supply your muscles with the extra oxygen they’re now asking for. This process is not instantaneous. Depending on how much your pace increases, it may take your heart thirty seconds or more to settle into a new rhythm. Cardiac lag has important implications for heart rate monitoring during workouts that include changes in pace. For example, suppose you are doing a run that features six intervals of thirty seconds in Zone 5 with two-minute recoveries in Zone 1 between intervals. When you start the first interval, you will accelerate abruptly, and your heart rate will begin to climb. But chances are your heart rate will not actually reach Zone 5 until the very end of the thirty-second interval, if even then. That doesn’t mean you failed to do the interval at the right intensity. As long as you were running fast enough that your heart rate would have reached Zone 5 if you had continued at that pace, then you did it correctly. Likewise, when you slow down for recovery at the end of your first thirty-second Zone 5 interval, your heart rate will begin to decrease. But because of cardiac lag, no matter how much you slow down, your heart rate might not get all the way back down to Zone 1 before your two-minute recovery ends and it’s time to start the next interval. Again, this doesn’t mean you screwed up. As long as you jogged Zone 1 eventually, you did it correctly.”

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