Does a Strong Core Make You Faster?

Planks, dead bugs, Russian twists and Swiss ball routines are a fixture of many triathletes' weeks. Coaches and social media regularly present a strong core as the key to holding form late in the run, staying stable in the aero position and swimming with better body position. The idea is intuitive: your trunk links your arms and legs, so a stronger, more stable trunk should transfer force better and waste less energy.

It's a good hypothesis. The question is whether training the core actually makes you faster, and that's where the evidence is thinner than its popularity suggests. Core training reliably improves the things you'd expect it to improve, such as plank times and trunk strength. Whether those changes carry over into swimming, cycling or running performance is much less certain.

This article looks at what the systematic reviews conclude, what the small trials in runners, cyclists and swimmers found, and where core work is worth keeping in a triathlete's week. TriForward's "The Minimum Effective Dose" covers how to fit strength work into a busy week, and TriForward's guide "Heavy Lifting for Bike Power" covers the stronger evidence for heavy lower-body lifting.

What "core training" means

There's no single definition, which is part of the problem. In research and in practice, "core training" can mean:

• Core stability work: holding positions against gravity or resistance, such as planks, side planks, bird dogs and dead bugs.
• Core strength work: moving the trunk against load, such as weighted back extensions, cable rotations or hanging leg raises.
• Unstable surface training: exercises on Swiss balls, wobble boards or other unstable surfaces.
• Integrated work: whole-body lifts such as squats, deadlifts, carries and single-leg exercises, which load the trunk muscles while training the legs.

Different studies use different combinations, and measure the core in different ways. That makes it hard to compare results, a point the reviews below make repeatedly.

Why the idea is so popular

The theory behind core training draws on a few plausible ideas:

• Force transfer. In running and swimming, force moves between the legs, trunk and arms. A trunk that moves too much might absorb some of that force.
• Posture and alignment. If your trunk tires, your pelvis and hips may move more, which might change how your legs work.
• Injury. Core weakness has been linked to some lower-limb and back problems, although that's a separate question from performance.

None of this is unreasonable. But a mechanism being plausible doesn't tell you how large the effect is, or whether a specific core routine produces it.

The 2012 systematic review: marginal benefits

The most cited review is by Reed, Ford, Myer and Hewett in Sports Medicine in 2012. They screened 179 articles and included 24 studies with a core-focused intervention and an athletic performance outcome. Studies with participants aged 65 or older were excluded.

• 8 studies looked at general performance, 10 at lower-limb performance and 6 at upper-limb performance.
• Most studies combined core training with other exercise. In these, gains often appeared in general strength measures such as squat load and vertical jump, which makes it hard to credit the core work.
• Not all studies showed improvements in core strength or stability themselves.
• Studies where the core was the main target had mixed results.

The authors concluded that targeted core stability training provides marginal benefits to athletic performance. They pointed to conflicting findings and a lack of standard ways to measure the core or to prescribe core training.

The 2025 review: core tests and sprints

A 2025 systematic review by Bustos Carvajal and Arias Coronel in Frontiers in Sports and Active Living looked at more recent trials. It included 7 controlled trials in competitive athletes, mostly in soccer, volleyball, basketball, badminton and martial arts, with one in runners. Participants were mostly male, and some samples included adolescents.

• Core training improved trunk extensor strength, core endurance, dynamic balance and sprint speed.
• Results for trunk flexor strength, jump height and agility were inconclusive.
• Study quality was moderate, with an average PEDro score of 5 out of 10. Common weaknesses included lack of blinding.

The review supports the idea that core training improves the core. Its performance outcomes were mainly short sprints and balance in team sports, which are a long way from a two-hour triathlon.

Runners: one positive trial, one negative

The Swiss ball trial. A 2004 study by Stanton, Reaburn and Humphries in the Journal of Strength and Conditioning Research tested 18 young male athletes averaging 15.5 years old. Eight did Swiss ball core training twice a week for 6 weeks; ten acted as controls.

• Core stability improved in the training group.
• There was no change in running economy, VO2max or running posture, and no change in abdominal or back muscle activity measured by EMG.

The authors concluded Swiss ball training may improve core stability without improving physical performance, and suggested choosing exercises more specific to the sport.

The 5,000 m trial. A 2009 study by Sato and Mokha in the same journal randomised 28 recreational and competitive runners with an average age of about 37. Twenty completed the study, 12 in the core training group and 8 in the control group. The training lasted 6 weeks.

• The core training group ran 5,000 m faster after 6 weeks.
• There was no change in ground reaction forces while running, or in lower-limb stability measured by a balance test.

The abstract doesn't report the sex of the participants or the size of the improvement. The 2025 review above, which included this trial, noted that the control group also improved significantly. Inference: with 20 finishers, an uneven drop-out and improvement in both groups, this trial is suggestive rather than convincing. It also found no change in the mechanisms usually proposed for core training's benefit.

Running economy: a small positive signal

A 2019 trial by Hung and colleagues in PLoS ONE studied 21 male college athletes. Eleven added three core training sessions a week for 8 weeks to their usual training; ten continued as normal.

• Plank endurance improved in the core group, from an average of 193.5 to 241.5 seconds.
• Static balance scores improved, from 78.8 to 85.3.
• Heart rate was lower in the first three stages of a treadmill test, and oxygen use at the fourth, fastest stage fell from 52.4 to 50.0 ml/kg/min.

The authors concluded core training may improve running economy. Inference: the change at the fourth stage is about 4.6% lower oxygen use, which would be meaningful if confirmed. But the abstract reports it as a before-and-after change within the core group, which improved while the control group didn't, rather than as a direct difference between groups. In 21 young men who weren't endurance specialists, it needs replicating before it's relied on.

Cyclists: what happens when the core tires

There's no published training trial showing core work improves cycling performance, but one study asked what happens to cycling mechanics when the core is tired. A 2007 study by Abt and colleagues in the Journal of Strength and Conditioning Research tested 15 competitive cyclists riding on a high-speed treadmill to exhaustion, before and after a core-fatiguing workout.

After core fatigue:

• Side-to-side knee movement increased from 15.1 to 23.3 degrees.
• Forward-and-back knee movement increased from 69.9 to 79.3 degrees.
• Ankle movement increased from 29.0 to 43.0 degrees.
• Pedal forces didn't change.

The authors suggested that core endurance might help maintain leg alignment on long rides. Inference: this shows that a tired core can change how your legs move on the bike. It doesn't show that core training improves power, speed or injury rates, and a deliberately exhausted core isn't the same as normal riding.

Swimmers: a sprint benefit

A 2015 trial by Weston and colleagues in the International Journal of Sports Physiology and Performance studied 20 national-level junior swimmers, 10 male and 10 female, aged about 16. Ten added isolated core training three times a week for 12 weeks to their pool training; ten continued pool training only.

• 50 m front crawl time improved by 2.0% relative to the controls (90% confidence interval −3.8% to −0.2%).
• Prone bridge time improved by 9.0%, and a core-specific pulling test by 23.1%.

This is one of the better-designed core studies, and it found a real performance benefit. But it was a 50 m sprint in young, competitive pool swimmers. Inference: whether core work helps an adult-onset triathlete over 1.5 km or 3.8 km in a wetsuit is unknown.

Why core tests and performance can diverge

It's worth asking why a programme can improve core strength without changing performance. A few explanations are plausible, though none has been tested directly in triathletes:

• Specificity. A plank holds a still position for a minute or more. Running, cycling and swimming need the trunk to stabilise against fast, repeated, changing forces for hours. Getting better at one doesn't guarantee getting better at the other.
• Enough is enough. If a trained athlete's trunk is already strong enough for their sport, extra core strength may add little.
• Measurement. Core strength is measured in many different ways, and the reviews above found no standard test. A change in one test may not reflect a change in what the trunk does during exercise.
• Time cost. Core sessions added to normal training are small. Any benefit is competing with the much larger effect of swim, bike and run training itself.

What this means for triathletes

Taking the evidence together:

• Core training reliably improves core strength and endurance tests. That's consistent across reviews and trials.
• Performance transfer is small, mixed and mostly short-event. The positive results are a 50 m swim, sprint speed in team sports and one small 5,000 m trial. The economy findings conflict.
• No trial has tested triathletes or long-course performance.
• Heavy lower-body strength training has stronger evidence for endurance performance. TriForward's guide "Heavy Lifting for Bike Power" covers a 2025 meta-analysis of 17 studies in cyclists.

Inference: a strong core is probably useful, but there's little evidence that adding separate core sessions makes a well-trained triathlete faster. It's more likely to be a small supplement than a performance driver.

A sensible place for core work

These suggestions are drawn from the evidence above. They're not a tested programme:

1. Prioritise heavy, multi-joint lifting. Squats, deadlifts, split squats and carries load the trunk as well as the legs.
2. Keep separate core work short. Ten minutes two or three times a week, often as part of a warm-up or at the end of a lifting session, is a reasonable amount.
3. Choose exercises that resist movement. Planks, side planks, dead bugs, bird dogs and carries train the trunk to stay stable, which is closer to what it does in swimming and running.
4. Include the back as well as the front. The 2025 review found clearer effects on trunk extensor strength than on flexor strength.
5. Don't trade key sessions for core work. If time is tight, a swim, bike or run session is likely to be worth more.

A triathlon scenario

The following example is illustrative, not drawn from a study. A 46-year-old woman training for her first Ironman notices her running form falls apart in the last hour of long bricks. She's been doing 30 minutes of planks and crunches four times a week, but hasn't done any lower-body strength training.

Based on the evidence above, she might:

• Replace most of her core time with two lower-body strength sessions, including squats or deadlifts and single-leg exercises, which also load her trunk.
• Keep a short core routine, perhaps 10 minutes of planks, side planks and back extensions after each lifting session.
• Look at fuelling, pacing and durability as likely reasons for late-run fade. TriForward's "Why the Ironman Marathon Falls Apart After 25 km" covers running durability.

Common mistakes

• Judging core training by plank time. It reliably improves plank time. That isn't the same as racing faster.
• Doing core work instead of heavy lifting. The evidence for leg strength training is stronger.
• Assuming unstable surfaces are better. The Swiss ball trial improved core stability with no change in running economy.
• Spending long sessions on the core. The trials used short routines added to normal training.
• Treating core training as a fix for back pain without getting assessed. That's a clinical question, not a performance one.

What we don't know

• Whether core training improves triathlon performance at any distance, since no trial has tested it.
• Whether core training helps adult open-water swimmers, rather than junior pool sprinters.
• Whether a stronger core reduces late-race form breakdown in running or in the aero position.
• Whether core work adds anything to a programme that already includes heavy lifting.
• How results differ by sex, given that most participants were male.

References

• Reed CA, Ford KR, Myer GD, Hewett TE. The effects of isolated and integrated 'core stability' training on athletic performance measures: a systematic review. Sports Medicine, 2012;42(8):697–706. doi:10.2165/11633450-000000000-00000
• Bustos Carvajal JS, Arias Coronel F. Exploring the role of the core in sports performance: a systematic review of the effects of core muscle training. Frontiers in Sports and Active Living, 2025;7:1630584. doi:10.3389/fspor.2025.1630584
• Stanton R, Reaburn PR, Humphries B. The effect of short-term Swiss ball training on core stability and running economy. Journal of Strength and Conditioning Research, 2004;18(3):522–528. doi:10.1519/00124278-200408000-00023
• Sato K, Mokha M. Does core strength training influence running kinetics, lower-extremity stability, and 5000-M performance in runners? Journal of Strength and Conditioning Research, 2009;23(1):133–140. doi:10.1519/JSC.0b013e31818eb0c5
• Hung KC, Chung HW, Yu CCW, Lai HC, Sun FH. Effects of 8-week core training on core endurance and running economy. PLoS ONE, 2019;14(3):e0213158. doi:10.1371/journal.pone.0213158
• Abt JP, Smoliga JM, Brick MJ, Jolly JT, Lephart SM, Fu F. Relationship between cycling mechanics and core stability. Journal of Strength and Conditioning Research, 2007;21(4):1300–1304. doi:10.1519/R-21846.1
• Weston M, Hibbs A, Thompson K, Spears I. Isolated core training improves sprint performance in national-level junior swimmers. International Journal of Sports Physiology and Performance, 2015;10(2):204–210. doi:10.1123/ijspp.2013-0488