Jumping to Conclusions

MapMyRun’s Jump Around Recovery-Monitoring Feature is Sensitive to Neuromuscular Fatigue in Recreational Runners

Last year, we came out with a new connected shoe: the Gemini 2 Record. The awesome new features of this shoe come from the small chip embedded in the midsole, like measuring a runner’s speed, distance, and cadence during a run. On the MapMyRun team, we wanted to add a unique feature to our apps that would take advantage of this new connected shoe in an unexpected way. We thought: “What if we could measure your vertical jump, and from that, derive something about you?”

Many professional and Olympic teams use vertical jump performance—also known as “countermovement jumps”—to measure neuromuscular fatigue in order to prevent overreaching, i.e. too much fatigue. Until now, though, commercial systems that measured vertical jump performance could cost up to $5,000. So our goal became clear: to democratize information usually reserved for elite athletes, enabling athletes of all levels to train smarter.

But would it work? If we measured your vertical jump performance from the little chip embedded in our shoe, would it tell us anything about your neuromuscular fatigue, even if you were a recreational runner? To answer these questions, we ran a study, which had these primary objectives:

  • To guide the software integration of our new Jump Around feature within MapMyRun.
  • To investigate the relationship between vertical jump performance and the more traditional tools of self-reported and heart-rate-based measurements as runners were exposed to variable training loads.

Background

Jump Around is a footwear-integrated digital self-testing tool designed to assess neuromuscular fatigue by measuring the flight time of a series of six repeated vertical jumps. Whew—that’s a mouthful. Basically, you tell our app that you’re going to jump, you jump six times, and we tell you what we find.

We know that fatigue monitoring via vertical jump performance has been validated by existing studies, and has been reinforced by interviews with coaching practitioners in elite sport (e.g. UA Ski & Snowboard, Canadian Sport Institute, Liverpool John Moores University, IMG Academy, Notre Dame University), but many questions remained about how to serve up this feature to our typical runners.

Our Hypotheses

  • Jump scores—measures of neuromuscular fatigue—will vary with each runner’s training phase and as a function of each runner’s adaptations to variable running loads.
  • Jump scores will correlate directly with self-reported (fatigue, soreness) and heart-rate-based measurements.

Our Methods

Eleven runners (two female, nine male; average age 33) were enrolled in the study. Each runner was at least moderately trained, and regularly incorporated running into their training regimen. Weekly mileage ranged from 10 to 60 miles per runner. Runners’ race experience ran the gamut between marathons, 10k races, Half Ironmans, and Spartan races.

Runners were enrolled in a six-week program designed with sufficient training loads to deliberately induce counterproductive fatigue levels—we ran them too hard, on purpose. For science. Training was divided into three two-week phases: (1) baseline training, (2) overload training, and (3) active recovery. The runners were surveyed each weekday as to their perceived level of stress, sleep quality, muscle soreness, and general fatigue. Runners also performed the Jump Around jump test before and after a 3-minute warmup. Lastly, we captured heart rate measurements, including resting heart rate, running heart rate (85% estimated VO2 max), and recovery heart rate (recorded one minute after a steady-state treadmill run).

What We Found

During overload training, post-warmup jump performance got worse throughout the first week, likely because of the cumulative effects on the runners from our high-intensity training. Reduced jump scores also coincided with reduced running performance (they got slower) and an overall increase in runners’ self-reported muscle soreness and fatigue (they felt more pain and weakness). Heart rate measurements also jumped, but in the second week of overload training, a response that was unexpectedly delayed.Jump performance began to return to baseline levels during the second week of overload training even as load remained high, suggesting that the runners were adapting to the higher training load. But they were still sore during the whole overload training phase. This finding is consistent with published research showing that muscles soreness peaks after athletic performance begins to rebound.

Weekly and overall study trends

Research has shown that recreational runners often experience large week-to-week changes (>10%) in training load. Fluctuations in load have also been shown to increase the risk of illness or injury. So, practical tools that inform a runner about their fatigue would be awesome to build into their training plan.

Using heart-rate-based measurements to monitor fatigue might actually be less informative than tracking jump scores, since heart rate measurements may lag, as we saw in our study. The Jump Around feature appears to offer a better fatigue indicator because jump scores alert runners before their cumulative fatigue levels get too high. Our study also showed that jump score measurements were sensitive enough to detect both fatigued and recovered muscles. Runners would be smart to use our Jump Around feature to monitor their recovery and optimize their training, especially when compared with the complicated and burdensome heart rate measurements often used. Our findings are worth exploring further, in a longer study with a larger sample of athletes.

Jump scores are most informative when conditions and effort are consistent. Consistency gives the necessary baseline of scores, allowing good conclusions to be drawn from deviations from that baseline. Daily jump testing is recommended, and a minimum frequency of every third day is required to use your jump scores as a relevant performance reference. Athletes should also maintain consistent behaviors beforehand for best results.

Test with or without warmup? For time-constrained runners, there is, at most, a small boost in jump scores (1–3%) gained from warming up. Consistent jumping conditions are more critical than a warmup, so runners could perform the test with just a few priming jumps. However, conducting Jump Around with a warmup is recommended for competitive runners seeking greater fatigue sensitivity, assuming their warmup is reproducible.

Takeaway

For a small sample of recreational runners tracked over six weeks of variable training load, vertical jump scores measured with Under Armour’s connected shoe are reliable, sensitive measures of neuromuscular fatigue.

Check out the latest version of MapMyRun and the growing set of connected shoes we now offer! You can also download a PDF copy of our study.

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