Running Economy Beyond the Treadmill: A Two-Condition Lactate Study in Orienteers

Background & Motivation

In the history of sport, many methods have been used to predict performance based on physiological signals. In running, recent studies have shown that speed at the anaerobic lactate threshold (vLT2) is highly correlated with running race performance in track and road running events (Ji et al., 2021). However, in orienteering the picture is not so clear, with limited study on how well treadmill vLT2 transfers over to the demands of uneven surfaces of trail and off-trail running. This study aims to understand the significance of vLT2's effect on orienteering performance and begin to identify how strong of a relationship actually exists between treadmill and forest running.

Research Question

Primary: How strongly does vLT2 (treadmill lactate threshold) correlate with vLT2 measured under forest, off-trail conditions in trained orienteers?

Secondary question:

• To what extent does terrain cost account for the difference between C1 and C2?

Note: An earlier version of this design included a third condition (orienteering intervals with navigation) to isolate cognitive/navigation load as a separate factor from terrain. That condition was dropped because navigation-based intervals are difficult to standardize across athletes and repeats — route choice, mistakes, and variable leg lengths make it hard to control for intensity and comparability. The cognitive-load question is left for a follow-up study built on these results.

Study Design

Two within-subject conditions, same participants across both sessions. Sessions spaced 2–3 weeks apart, order counterbalanced across participants where possible.

C1 — Treadmill. Participants will complete a staged treadmill protocol consisting of a 10-minute easy warm-up followed by 5 intervals of 5 minutes at increasing intensity with 2 minutes rest between intervals. Based on the athlete's estimated lactate profile from previous testing, training, or races, the treadmill speed will be calibrated to try to measure the athlete's blood lactate at ~1.5–2.0 mmol, ~2.0–2.5 mmol, ~2.5–3.5 mmol, ~3.5–5.0 mmol, and ~5.0+ mmol, with some flexibility available for adjusting speeds based on the initial few readings.

C2 — Forest (Marked Route). Participants will complete a similar protocol to above involving a 10 minute warm-up then 5 intervals on a marked forest route which will take roughly 4–6 minutes with 2 minutes of rest between intervals. This route will be completed 5 times at increasing intensity, aiming for a similar lactate profile to the treadmill test of ~1.5–2.0 mmol, ~2.0–2.5 mmol, ~2.5–3.5 mmol, ~3.5–5.0 mmol, and ~5.0+ mmol.

Participants

Inclusion criteria

• Active orienteer with club membership
• Lactate threshold pace ≥16 km/h (men) or ≥14 km/h (women), verified in C1
• Currently healthy and training normally

Exclusion criteria

• High intensity training or racing within 48 hours of any test session
• Cardiovascular or metabolic condition affecting lactate response
• Unable to complete both sessions within the study period

Target sample

N ≥ 10 men, N ≥ 10 women. Recruitment via Gothenburg-area orienteering clubs.

Measurements & Variables

Cost Analysis

Consumable costs are based on N = 25 participants completing five intervals across two conditions (10 measurements per participant with 2 extra for buffer, 300 total). Prices are estimated from the expected provider https://www.lactateplus.de/. Equipment (lactate meter, GPS watches, heart rate monitors, etc.) is provided by investigators and not included here.

Analysis

• Lactate curves fitted per athlete per condition (3rd or 4th order polynomial)
• LT2 speed derived per athlete per condition (speed at 4 mmol/L)
• Spearman rank correlation between LT2 speeds across C1 and C2
• ICC for lactate agreement at matched intensities across C1 and C2
• Bland–Altman plots for C1 vs C2 agreement
• Effect sizes (r, ICC with 95% CI) reported as primary outcomes given N=20

Timeline

Ethical Considerations

• Informed consent obtained from all participants prior to first session
• Participants may withdraw at any time without consequence
• Data stored anonymously; participants identified by code only
• Lactate sampling is minimally invasive (fingertip pinprick); proper safety protocols with lancets and sterilization

Limitations

• Self-supported design limits protocol control compared to a fully funded and supervised lab study
• Sample and sessions restricted to Gothenburg area; findings may not generalise broadly
• Pacing in C2 is athlete-controlled, introducing variability between stages and potential difficulty in hitting intensity targets on uneven terrain
• N ≥ 10 per sex provides limited statistical power; study is framed as a pilot
• Dropping the navigation condition (C3) means the study cannot speak to the cognitive-load component of orienteering performance — only to terrain cost. This is a deliberate scope reduction, not an oversight

References

Ji, S., Sommer, A., Bloch, W., & Wahl, P. (2021). Comparison and performance validation of calculated and established anaerobic lactate thresholds in running. Medicina, 57(10), 1117. https://doi.org/10.3390/medicina57101117