We are all busy but know the importance of regular activity. Some days, the plan to workout doesn't happen or the amount of time you have is cut short. So how do you adjust your workout to make the most of it, especially on interval day?
Too often, I see athletes cut the warm up or cool downs short. This isn't ideal since your body needs time to get ready for more strenuous efforts. It takes time for blood flow to increase in your muscles. Once that happens your muscles will be warmer which allows for better oxygen uptake and contractions and releases can happen more quickly. Throughout your warm up, you slowly increase range of motion which can help you avoid injuries. I normally recommend a 15 minute warm up but if you are pinched for time, allow at least 10 minutes.
Cool downs are just as important, especially when the intensity is really high. The high intensity generates a lot of Lactate. The cool down process actually trains your body to better process and clear Lactate. Let's take a closer look at intervals and the recovery interval to cover the finer details.
Your intervals should generally be very hard efforts. Hard efforts train your body to move faster: everything from stronger muscle contractions, more efficient muscle recruitment, more efficient form, and greater energy production requirements. Your races will always be a fraction (hopefully a big fraction!) of your top end speed so it makes sense to try to push that top end speed higher.
There may be times in a race where you need to go above threshold, the point where the pace/power/effort can't be sustained for the remainder of the race and you will have to slow down. This could be a hill, group sprint, or clearing the drafting zone within time constraints. The longer you spend above threshold and the higher above that threshold you are, the harder it is to recover mid-race. That's where the recovery interval comes in.
Because your intervals are very hard, they are substantially above threshold. Once the interval ends, your body starts working toward recovery and below threshold steady-state. If you can keep moving during that recovery, assuming you are below threshold, your body will actually process and convert Lactate more quickly and you'll return to a sustainable state faster. Intervals specifically train this process of recovery so that you can more quickly recover from above threshold states you'll experience in a race.
While the hard effort is important, it's also important to look at the recovery between intervals. The recovery interval and recovery effort should be such that your hard efforts can be maintainable throughout all the reps and for the full duration of each interval. If you use a heart rate monitor, you can monitor your bodies recovery process.
Take a look at the HR graph above from my bike intervals on Sunday. You can clearly see the increased workload for the 6 intervals. The rest interval on these was 5 minutes with the goal of being fully recovered for the next one. You can see that my HR does indeed come back into Z2 (where I warm up and cool down) within about the first 3 minutes of all rest interval.
Now look at the speed at which my HR recovered over those 6 intervals. You can see on the first one that it drops immediately and nearly back to Z2 within the first minute or 90 seconds. As you compare the first to the later intervals the recovery takes a little bit longer each time. This is due to increased fatigue from each interval before it. If the rest interval wasn't long enough, I would not be fully recovered. This has a two-fold effect. First, on later intervals, I might not be able to hit the target watts designed to train my body to go harder and build high end power production. Second, because I am not fully recovering, I'm losing the opportunity for the adaptation of faster recovery. As I add more intervals or increase power later in the season, I would look to see that my HR is dropping more quickly in later reps to validate that by body can recover faster and therefore race faster.
Getting back to the question of being short on time... If the goal is short, fast/high power intervals you want to make sure you are warmed up for them and recovered after so keep warm up and cool down to at least 10 minutes. Don't reduce the power/pace of the interval, in fact, if you know you are definitely doing fewer intervals you could actually increase the pace or power slightly. The time savings comes in by shortening your recovery interval, but only as short as will allow for you to be fully recovered, generally having your HR return down to Z2, before starting the next interval.
So, in my example, my first few recovery intervals could have been 2 or 3 minutes, but I would ensure my HR recovered back to Z2. In later intervals, I might have to increase that recovery interval to 4 or even 5 minutes.
This might not seem like much time savings, but it could get you 6 repeats instead of 5, when you were supposed to do 8. My hope is that it encourages you to get out even if you know it won't be the full workout. Use your data to the best of your ability to consistently move you toward your goal. Even if you are short on time.