Jumping to Conclusions? What Countermovement Jumps Really Tell Us About Trail Running Fatigue | Find Your Stride | Edinburgh Podiatrist

Introduction

Every runner has experienced it. You cross the finish line feeling surprisingly strong, only to discover five or ten minutes later that your legs suddenly feel like concrete. This new study investigates exactly that phenomenon by examining how young trail runners respond immediately after competition using two familiar tests; the squat jump (SJ) and countermovement jump (CMJ).

Rather than finding immediate fatigue, the authors observed a brief improvement in jumping performance before fatigue became apparent several minutes later. It’s an intriguing finding with genuine implications for coaches, clinicians and runners, but like many sports science papers, the conclusions deserve careful interpretation.

Trail running doesn’t tire you immediately - or does it?

What did the researchers do?

The authors recruited 36 highly trained trail runners aged 15–20 years (29 males and 7 females). Each athlete completed:

• Squat Jump (SJ)

• Countermovement Jump (CMJ)

  
  

at three time points:

• One hour before a race

• Within approximately two minutes of finishing

• Five to seven minutes after finishing

  
  

The race itself covered 14.2 km with 420 metres of ascent, representing a relatively short but demanding trail event. Jump performance was measured using a validated Chronojump Bosco platform.

What did they find?

The headline finding is surprisingly simple. Immediately after finishing:

• SJ increased significantly.

• CMJ also increased significantly.

  
  

Five to seven minutes later:

• Both measures dropped below baseline.

• The “elastic component” (the difference between CMJ and SJ) remained unchanged.

  
  

The authors argue that the immediate improvement reflects post-activation performance enhancement (PAPE) rather than true recovery. Once this temporary boost fades, underlying neuromuscular fatigue becomes apparent.

What does this mean for runners?

This is arguably the strongest practical message from the paper. Many coaches use CMJ as a quick measure of fatigue. However, if testing occurs immediately after exercise, athletes may appear more powerful than before they started, despite accumulating significant physiological fatigue. In other words: The timing of the test matters just as much as the test itself. For clinicians monitoring rehabilitation, return-to-running programmes or heavy training blocks, this is an important reminder that neuromuscular assessments are highly sensitive to when they are performed.

Where the study is strongest

It investigates an under-researched population. Most fatigue studies examine adult marathon or ultramarathon runners. Young competitive trail runners have received surprisingly little attention despite their rapidly increasing participation. This study therefore fills a genuine gap in the literature.

The design is clinically relevant

Rather than simply measuring pre- and post-race values, the researchers included a second assessment five to seven minutes later. That small methodological decision completely changes the interpretation. Without that extra measurement, the study would have concluded that trail running actually improves explosive performance. Instead, it demonstrates that fatigue can initially be masked.

The findings align with previous research

The authors compare their results with previous work showing similar transient improvements after mountain running and loaded military running before delayed fatigue becomes apparent.

This strengthens confidence that the phenomenon is real rather than a statistical anomaly.

But there are important limitations

Despite producing interesting findings, the study has several weaknesses that limit how widely we should apply its conclusions.

1. The sample size is small

Thirty-six athletes sounds reasonable initially. However, only seven were female. This makes meaningful gender-specific conclusions difficult, particularly when discussing neuromuscular adaptations. The authors report no interaction between gender and fatigue, but the study is probably underpowered to detect one.

2. These weren’t typical recreational runners

Participants belonged to a regional trail running development programme, with several competing at elite youth level. Most runners reading this blog will:

• be older

• train differently

• recover differently

• have different injury histories

  
  

Therefore, the findings may not transfer directly to recreational trail runners.

3. The race was relatively short

A 14 km race with moderate climbing represents a very different physiological challenge compared with:

• mountain marathons

• ultramarathons

• multi-day events

  
  

Longer races typically produce much greater muscle damage and neuromuscular impairment.

It’s entirely possible that immediate potentiation disappears altogether during much longer races.

4. Jump height tells only part of the story

Perhaps the biggest limitation is acknowledged by the authors themselves. Jump height alone is increasingly recognised as an incomplete fatigue marker. Modern force platforms provide variables including:

• Reactive Strength Index (RSI)

• force development

• braking impulse

• eccentric duration

• concentric power

• force-time characteristics

  
  

Previous research has shown that athletes can maintain jump height while altering movement strategy substantially. Consequently, relying solely on jump height risks overlooking meaningful neuromuscular fatigue. Ironically, this paper reinforces that very point.

5. No injury or performance outcomes

The study demonstrates changes in jump performance. What it doesn’t show is whether those changes:

• predict injury,

• influence recovery,

• affect future training quality,

• or relate to subsequent race performance.

  
  

Until those links are established, jump testing remains a useful monitoring tool rather than a definitive guide for clinical decision-making.

What does this mean for podiatrists?

This study has several practical implications for clinicians working with runners. If you’re using CMJ or SJ to monitor fatigue during rehabilitation or training:

• Avoid testing immediately after hard running.

• Standardise testing time across repeated assessments.

• Consider waiting at least 5–10 minutes after exercise if assessing acute fatigue.

• Interpret jump height alongside subjective fatigue, training load and clinical examination.

• Where available, use force-platform metrics rather than jump height alone.

  
  

For runners returning from injury, this reinforces an important concept: Feeling good immediately after exercise doesn’t necessarily mean your neuromuscular system has fully recovered.

Our Verdict

This is a thoughtful study addressing a genuine gap in trail running research. Its biggest contribution isn’t proving that trail running causes fatigue, we already knew that. Instead, it demonstrates when fatigue becomes visible, highlighting the transient masking effects of post-activation performance enhancement. For coaches and sports scientists, that’s valuable information. For podiatrists, it provides another reminder that timing matters when assessing function after exercise.

The study isn’t without limitations. The small sample, elite youth population and reliance on jump height alone reduce the strength of the conclusions. Nevertheless, it advances our understanding of fatigue monitoring and supports a more nuanced interpretation of jump testing in endurance athletes.

Find Your Stride!

Citation

Sanchez-Garcia, L. F., Molina-Garcia, N., & Jimenez-Olmedo, J. M. (2026). Acute neuromuscular responses in young trail runners: Immediate, post-, and delayed effects on squat and countermovement jump performance. Journal of Physical Education and Sport, 26(2), 234–240. https://doi.org/10.7752/jpes.2026.02027