• Training intensity distribution (TID)—how much time you spend in different training intensity zones is most important for maximizing training gains, according to the research published in the Journal of Strength and Conditioning Research.
• Cyclists in the study responded best to polarized training—spending more time in the harder and easier ends of the training intensity spectrum than the comfortably hard training intensities in between.

Our cycling forefathers rode more miles than seems humanly possible, but new research is confirming we should ride smarter, not longer.

When it comes to training, cyclists often turn to the gospel according to legendary Eddy “The Cannibal” Merckx: “Ride lots.”

Modern training tools and apps do their part to reward that two-word Merckx mantra. I mean, who doesn’t crack a smug little smile when they see a “Massive” or “Historic” Relative Effort on their Strava ride stats?

But a recent study from Ghent University questions the merit of judging your training solely by your training impulse score (TRIMP)—a popular measurement of training load based on heart rate, duration, and intensity. You may also see this listed as a Training Stress Score (TSS), a training load indicator similar to TRIMP, but one that is power-based, or Relative Effort (RE), Strava’s version of TRIMP.

In fact, the Belgian researchers concluded that “the commonly used TRIMP methods to quantify TL [training load] do not show a linear dose-response relationship with performance improvement in recreational cyclists.” Translation: Many “massive” relative effort rides will not automatically yield massive gains.

The study included 11 recreationally competitive cyclists, the average age of which was 40, who were just beginning spring training. All the riders were preparing for a hill climb in the Alps or Pyrenees.

Before the riders started training, the researchers put them through a battery of performance tests including lactate threshold, power at aerobic threshold, power at anaerobic threshold, max power output, and max heart rate. Then the researchers gathered the cyclists’ training data over a period of 12 weeks, from March to June.

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Over the course of the study period, the number of training hours the riders racked up ranged from a low of 52, or about four hours a week, to a high of 152, or about 12 hours a week, with the average coming in at 86 training hours, or about seven hours each week. TRIMP scores ranged from a low of 504, from the rider pulling the fewest hours, to 982 for the cyclist who rode the most.

When the researchers brought the cyclists back into the lab for follow-up testing, the riders had gotten fitter and stronger, but there was no significant correlation between their average weekly TRIMP score and how much their wattage had improved in any of the measurements.

What did matter was training intensity distribution (TID)—the time that the cyclists dedicated to riding at various intensities, or training zones.

The researchers examined the time the riders spent in three different zones: Zone 1, below aerobic threshold (where you can happily spin for hours), Zone 2, which is between aerobic threshold and anaerobic threshold (or comfortably hard), and Zone 3, which is above anaerobic threshold (or where the suffering really starts).

Those who spent the most time in Zones 1 and 3 instead of Zone 2 enjoyed significant gains in their anaerobic power. This training strategy is known as polarized training, which involves alternating between pretty hard and pretty easy days.

The trouble is, if you just look at TRIMP, RE, or TSS, as a whole, you miss those finer details.

For instance, you can get a TRIMP score of 180 by riding for three hours easy or by spending one hour, a third of that time, hammering. So if one rider racks up a monster training stress score by riding 20 hours a week, while another hits the same number riding a fraction of that time but twice as hard, the performance gains will clearly not be the same.

That’s something Taylor Thomas of Thomas Endurance Coaching in Livingston, Montana sees a lot.

“I talk to athletes every day who see TSS and think if they just do more, they’ll get fitter,” he says. “That’s not true. TSS is simply a way to quantify training load. You may have a 1200 or 1500 TSS score, but if it’s not coming from the right place, you won’t have race results or be more fit for what you’re trying to accomplish.”

That’s where individualized training, periodization, and specificity come in. This study, as well as previous research, confirms what coaches know and preach: To maximize training adaptations, the distribution of training time over the intensity zones is most important.

Hunter Allen, CEO of Peaks Coaching Group and author of Training and Racing with a Power Meter, is one of those coaches. He says that when your overall TSS or TRIMP is the sum of the right parts, results follow. “I have thousands of athletes that I can directly correlate their TSS (and Training Load) values to their improvements when they have the right training composition to get that number.”