Why Running Slow Makes You Faster: The 80/20 Training Method That Changes Everything

2025 closes with stellar gains despite year-end profit-taking

The quick scan: Markets wrapped 2025 on the final trading day with modest declines as tax-loss harvesting and profit-taking dominated thin holiday volumes, but the year's spectacular performance remained intact. All three major indices notched double-digit annual gains for a third consecutive year despite April's tariff-induced correction and ongoing concerns about concentrated AI leadership.

S&P 500: -0.74% to 6,845.50 – closed the year with a 16.39% gain, marking its third straight double-digit annual advance and capping a volatile year that saw the index reach 39 record closes despite the April tariff shock that triggered a 10% correction
Dow Jones: -0.63% to 48,063.29 – ended 2025 up 12.97%, somewhat restrained by limited tech exposure but recovering impressively from spring's tariff turmoil, with Nike gaining 2% on the final day following insider buying
NASDAQ: -0.76% to 23,241.99 – led declines on profit-taking in semiconductor names like Western Digital and Micron after their triple-digit 2025 gains, but closed the year up 20.36% on sustained AI enthusiasm despite recent volatility

What's driving it: Classic year-end mechanics dominated the final session – tax-loss harvesting hit 2025 laggards hard while fund managers engaged in window dressing to showcase winners in annual reports. Trading volumes ran at just 50% of the 20-day average as most investors had already closed books. The year's winners were extraordinary: Palantir surged 139%, AMD climbed 78%, Nvidia gained 39%, while Western Digital skyrocketed nearly 300% and Micron jumped 250%. But concentration risk loomed large, with a small group of mega-cap stocks accounting for most of the S&P 500's gains – reminiscent of the "Nifty Fifty" era. Real estate languished as the year's worst sector, up just 0.5%.

Bottom line: Four consecutive down days couldn't diminish a stellar year – S&P 500 up 16%, NASDAQ up 20%, Dow up 13%. For L-Plate Retirees watching portfolios at or near record highs, today's fitness theme about running slow to go fast mirrors market wisdom: sometimes the smartest move is deliberately tempering intensity. The year's massive gains came despite (or because of) periodic pullbacks that let the system recover. Markets, like runners, need easy days to make the hard days worthwhile. Here's to 2026.

Running Slow Makes You Fast

The scoop: When people start running longer distances, the goal seems obvious: go as fast as possible for as long as possible. Push harder every session. Beat yesterday's time. Make every run count.

The problem? This approach leads to stalled progress, not improvement. Instead of getting faster, you feel more fatigued and sore. You plateau. You get injured. The very thing you're doing to improve – running hard constantly – becomes exactly what prevents improvement.

As counterintuitive as it sounds, achieving faster times requires much slower runs. Not some of the time. Most of the time.

The 80/20 principle

"The value in running slow is so you can run fast," explains Ben Rosario, professional running coach and Executive Director of the HOKA NAZ Elite running team.

Here's the framework elite runners and everyday athletes follow: 80% of your runs should be slow (or "easy"), at or below your aerobic threshold. High-effort sessions – sprint repeats, interval training – compose the remaining 20%.

Dr. Stephen Seiler studied elite endurance athletes and found this 80/20 split consistently among the best performers. Matt Fitzgerald later popularized the approach in his book 80/20 Running.

If you're training five days weekly, you get one hard day and four easy workouts. Three days? One hard, plus a medium shakeout and a long run. The structure changes, but the principle remains: most runs should feel easy.

Why maxing out every session backfires

Rosario points out a telltale sign of overtraining: when all runs happen at the same pace. This medium-everywhere approach means you never truly recover, but you also never reach your genuine top speed. You're perpetually operating in a gray zone that produces neither the recovery benefits of easy runs nor the performance gains of proper speed work.

Maxing out your body on every outing takes a brutal toll on muscles, tendons, and ligaments. Brad Whitley, physical therapist at Bespoke Treatments, confirms: "Generally, if people are including easy runs in their training consistently, they tend to be less injured."

When you run fast, you create more force on every stride. That amplified impact hits bones, tendons, and ligaments harder. "The more times you run faster, putting your joints under that load, cumulative stress will compound and you could increase your risk for injury," Whitley explains.

The mitochondrial advantage

Easy running isn't just about injury prevention. It's about building the engine that makes speed possible.

"You're actually training a very specific system in your physiology to operate at a low heart rate," Whitley notes. This is Zone 2 training – sustained exercise at roughly 72-82% of your max heart rate.

When you train in Zone 2, you build mitochondria – the cellular powerhouses that produce energy. More mitochondria means more energy production and better recovery. This adaptation doesn't occur at higher speeds. Your slow workouts affect your body in ways your fast ones won't.

Sprint workouts test how fast your car can go. Zone 2 training upgrades the engine itself. Both matter, but you need more of the second than the first.

The talk test trumps pace

Forget trying to define "slow" or "fast" based on finishing times. Think about effort instead.

Jes Woods, a Nike Running coach, actively avoids the term "slow." Instead, she calls these workouts "easy runs." The point is low effort. Your "slow pace" might feel easy one day. Run that same pace after poor sleep, and it no longer feels easy. Pace is relative. Effort is what matters.

The simplest gauge? The talk test. "If you can't hold a conversation, then you're not running slow," Rosario confirms. This is also called conversation pace, which makes easy runs more enjoyable since you can talk to friends while training.

For those who prefer biometrics, heart rate provides reliable data. A simplified approach: subtract your age from 180. If you're 55, your easy run threshold is roughly 125 beats per minute. Stay below that number.

Structure matters more than willpower

Rosario's rule: "I never have two days in a row that are hard or fast. There's always got to be at least one, if not two, slow/easy days in between."

This forces recovery. Structure removes the need for willpower. If you track weekly totals, aim for at most two hard workouts per week. The rest? Easy days and rest days.

The key is making easy days genuinely easy. Not "trying to go easy but still pushing pretty hard." Actually easy. Conversational. Below your aerobic threshold. The kind of pace where you could maintain it indefinitely.

Why this feels wrong

Breaking the "workouts should feel hard" mindset takes deliberate effort. Woods admits: "I have all of these analogies and coach-isms because historically, it's been difficult to convince runners to actually slow down."

Culture reinforces this. We celebrate PBs. We track every run on apps that highlight when we've gone faster. The entire ecosystem encourages speed.

But elite runners – the people actually winning races – spend most training time running slowly. They save intensity for specific workouts where it matters. They understand that sustainable improvement requires patience.

You're not getting slower by running easy. You're building the foundation that makes genuine speed possible. The mitochondria that produce energy. The cardiovascular capacity for sustained effort. The muscular resilience to handle hard workouts when they arrive.

Fast runs test the engine. Easy runs build it. Both matter. But you need more of the second than the first.

Actionable takeaways for L-Plate Retirees:

• Follow the 80/20 rule religiously. Make 80% of runs easy (at or below aerobic threshold), with only 20% as high-effort sessions.

• Use the talk test to gauge effort. If you can't hold a conversation while running, you're going too hard.

• Calculate your easy run heart rate ceiling. Subtract your age from 180 to get rough aerobic threshold. If you're 60, keep easy runs below 120 bpm.

• Never schedule back-to-back hard days. Always include at least one easy day (preferably two) between high-intensity sessions.

• Understand easy runs build the engine. Zone 2 training creates mitochondria that produce energy and improve recovery – adaptations that don't occur at higher speeds.

• Embrace that "easy" means genuinely easy. Not "trying to go easy but still pushing." Actually easy. The kind of pace you could maintain indefinitely.

Your Turn:
Looking at your current running routine, what percentage of your runs are genuinely easy versus medium-hard or hard – and does it match the 80/20 principle?
What makes it difficult for you to run truly easy – is it ego, social pressure from tracking apps, or the belief that workouts only count if they hurt?
If you committed to making 80% of your runs conversational pace for three months, what do you think would happen to your speed, injury rate, and enjoyment?

👉 Hit reply and share your story – your insights could inspire fellow readers in future issues.

If this counterintuitive approach to running faster resonates with you, consider supporting me on Ko-fi. Your contribution helps us keep sharing the science-backed strategies that challenge conventional wisdom – because sometimes the smartest path forward means deliberately slowing down.

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