Kiplimo trains with a smartwatch

A marathon is 26.2 miles of trying not to go 1% too fast too early. Jacob Kiplimo says he now uses a wristwatch to watch that margin in real time as he prepares for the 2026 London Marathon on April 26. (samsungmobilepress.com) (worldathletics.org) The key number is pace tied to strain, not just pace alone. Kiplimo told Samsung he checks heart rate, recovery signals, and running-form data from a Galaxy Watch8 to decide when to push and when to back off. (samsungmobilepress.com) One of those signals is asymmetry, which is a left-right balance check like noticing one shopping cart wheel pulling harder than the other. Samsung says Kiplimo tracks asymmetry with pace and heart rate to spot small form changes before they turn into slower sessions or injury trouble. (samsungmobilepress.com) Another signal runners obsess over is lactate threshold, which is the effort level where your legs stop feeling controlled and start filling with debt. Garmin’s running science notes that threshold is estimated from heart rate and pace, and experienced runners often sit near about 90% of maximum heart rate at that line. (garmin.com 1) (garmin.com 2) That matters in the marathon because the race is usually run just under that red line. Garmin says a marathon runner who goes about 5% above threshold may only hold that pace for around 20 minutes, which is why “a little too hard” early can wreck the last hour. (garmin.com) Kiplimo is a good test case because he is already one of the fastest road runners alive. London Marathon Events said this month that he arrives as the half marathon world-record holder at 56:42 and the reigning Bank of America Chicago Marathon champion. (londonmarathonevents.co.uk) His own training details show how ordinary the device has become in elite prep. Samsung’s interview says he covered more than 100 kilometers in one week, and even a “rest day” in his plan can still include a 3 kilometer run. (news.samsung.com) The bigger shift is that wearables are no longer being sold only as fitness bracelets for casual users. Garmin, Polar, and Samsung all now pitch watches around threshold, recovery, heart-rate variability, and running-form analysis, which are the same categories coaches use to structure serious training blocks. (garmin.com) (polar.com) (samsungmobilepress.com) That does not mean the watch replaces a coach. Polar’s coaching guidance says perceived effort still matters, which is another way of saying the numbers help most when they confirm what the runner already feels in the legs and lungs. (polar.com) Kiplimo’s London debut is where the marketing pitch meets the hard part of the sport. He told the elite men’s press conference that the half marathon is “not like the full marathon,” and that difference is exactly why elite runners now want a device on the wrist that can turn every training run into a lab test. (londonmarathonevents.co.uk)