A quick scan of what happened over the past week.

• Kelly and Sheridan Win the HYROX APAC Championships in Brisbane — The third and final Regional Championship of the season wrapped up in Brisbane this weekend, with the Elite 15 title and a World Championship qualifying spot on the line. Australia's James Kelly took the men's race in 55:25, pulling away from Dexter Buchanan (57:12) and Jonathon Wynn (57:33) after a tight early battle. On the women's side, fellow Australian Calypso Sheridan won in 1:00:33 in a race that stayed close through the first half, with Gabrielle Nikora-Baker second in 1:01:07 and Jess Pettrow third in 1:01:59. Both Kelly and Sheridan earn direct qualifying spots to the World Championships in Stockholm in June.

• Go One More Ultra: Still Running — The 2026 BPN Go One More Ultra began on Friday and is still underway at Bare Ranch in Liberty Hill, Texas. For the uninitiated: this is a backyard-style last-man-standing race where athletes complete a 4.2 mile loop every hour, on the hour, until only one person remains — everyone else receives a DNF. Costa Rica's Kendall Picado Fallas and American Mark Dowdle are the last two standing, both on lap 73 as of the time of publication (meaning they’ve run over 302 miles!). Last year's co-winner Kim Gottwald of Germany fell at 58 laps, as did ultrarunning legend Harvey Lewis. The race has no finish line — it ends when only one athlete is left standing.

Why building muscle and endurance simultaneously is harder than it looks — and what to do about it.

If you follow the world of hybrid training closely, you've probably noticed something. The athletes who built the biggest followings in this space — the ones who look the part and perform across both strength and endurance events — almost all came from a strength or muscle-building background first. That's not a coincidence. It's physiology.

The same is true for myself. I played college football, competed in CrossFit, and built a significant base of muscle mass before I ever started training seriously for endurance events. When I crossed the finish line at Ironman Arizona, I didn't look like a traditional Ironman athlete because I wasn't one for most of my training life. I was a strength athlete who got fit enough to run an Ironman. There's a meaningful difference.

The reason this matters is the interference effect — and understanding it will change how you approach your training.

What the interference effect actually is

In 1980, a researcher named Robert Hickson published a study showing that athletes who trained for both strength and endurance simultaneously gained significantly less strength than those who trained for strength alone. He called it the interference effect, and it's been studied extensively ever since.

The core problem is biological. Endurance training and strength training signal the body to adapt in opposite directions. Endurance training drives the production of mitochondria — the energy-producing structures inside muscle cells that power aerobic metabolism. Strength training drives muscle fiber growth and neuromuscular adaptations that increase force production. These two adaptations compete for the same cellular resources, and at high levels of training, they actively suppress each other. The more endurance volume you accumulate, the harder it becomes to build muscle — and vice versa.

The interference effect is most pronounced in the lower body, where both disciplines place the highest demand. Running is where it hits hardest. Cycling produces less interference than running because the muscle damage profile is different — which is worth knowing if you're trying to protect muscle while building aerobic capacity.

Why the famous hybrid athletes look the way they do

Here's the part that almost nobody talks about. The hybrid athletes you see on social media — the ones who are both jacked and fast — didn't build their physiques and their engines at the same time. They built one first, then added the other.

Most of them spent years in the gym building significant muscle mass before they ever started running long distances or training for endurance events. When they transitioned into hybrid training, they weren't trying to build muscle — they were trying to maintain it while improving their endurance. That is a fundamentally different and far more achievable goal.

Maintaining muscle while building an aerobic base is possible. Building significant muscle while simultaneously running high mileage and training for endurance is extremely difficult, and for most people at a serious training level, it's close to physiologically impossible to do both optimally at the same time.

This is also why the steroid accusations follow hybrid athletes so relentlessly. When someone sees a person who is visibly muscular completing an Ironman or posting fast HYROX times, the assumption is that the physique must be the result of PEDs — because intuitively, it doesn't seem like those two things should coexist. And while it may not be the case for everyone, it is possible to naturally build both muscle and fitness. The question isn't 'how did they build that much muscle while training for endurance?' The answer is they didn't — they built the muscle first, protected it carefully, and developed their engine around it.

The research bears this out — studies consistently show that concurrent strength and endurance training blunts hypertrophy and strength development compared to strength training alone, and the effect becomes more pronounced the more trained you are.

What to actually do about it: periodization

The answer isn't to abandon one discipline. It's to stop trying to maximize both at the same time and instead cycle through phases that prioritize one while maintaining the other. This is called block periodization, and it's how serious hybrid athletes should structure their year.

Phase 1 — Strength Focus (12–16 weeks) The primary goal is muscle building and strength development. Run enough to maintain your aerobic base — Zone 2 two to three times per week, nothing more. Keep mileage low and intensity lower. Lift four days per week with progressive overload, rep ranges that drive hypertrophy (6–12 reps), and enough calories to support muscle growth. This is where you actually add muscle. You won't lose your fitness. You'll maintain it.

Phase 2 — Base Phase (8–12 weeks) Both disciplines are weighted more equally. Strength work drops to two to three days per week, rep ranges shift lower (3–5 reps) to preserve strength without accumulating excessive fatigue, and running volume begins to build. This is the transition phase — you're preparing your body for higher endurance demand while protecting the muscle you built.

Phase 3 — Endurance Focus (10–16 weeks) The primary goal shifts to performance — whether that's a HYROX race, an Ironman, a marathon, or a 5K PR. Running volume and intensity are the priority. Strength work drops to two days per week, kept heavy and brief to maintain neuromuscular output without driving hypertrophy or generating excessive leg fatigue. You're not building muscle in this phase — you're maintaining what you have while getting faster.

Then cycle back to Phase 1.

The key takeaway

If you've been frustrated by your inability to get significantly bigger and significantly faster at the same time, the interference effect is likely the explanation. Your body isn't failing you — the plan is. Trying to maximize both simultaneously is fighting your own physiology. 

Choose a phase. Build muscle when you're building muscle. Get faster when you're getting faster. Maintain what you have when the focus shifts. The hybrid athlete who does this consistently will, over years, end up both stronger and faster than the one who tries to do everything at once.

For Lifts: RPE 5–6 — Moderate effort. Several reps left in the tank. RPE 7 — Challenging but controlled. This is the default working effort. RPE 8 — Hard. You could do more, but quality would slip. RPE 9 — Very hard. ~1 rep left. Near max for the day. RPE 10 — Max effort. Nothing left.

For Runs: RPE 4–5 = conversational Zone 2. RPE 6–7 = threshold, hard to hold a sentence. RPE 8–9 = race effort.

If you found this useful, forward to your training partners.

Train Hybrid,