Not all low-intensity rowing is the same: Self-paced intensity exceeds formula-based heart-rate–guided low-intensity on-water rowing in elite rowers.

Abstract

Introduction & Purpose

Low-intensity training dominates endurance training in elite rowing, commonly structured along intensity zones. These are often prescribed as percentages of maximum heart rate (%HR_max). Bishop (2025) suggests defining VeryLow, Low, and Moderate intensities relative to the first metabolic threshold (MT1), without clear cut between VeryLow and Low, and MT1 marking the upper boundary of Low. Given that minimizing Moderate-intensity training time may benefit elite endurance athletes pursuing a polarised training intensity distribution (Rosenblat et al., 2025), zone adherence is relevant. Whether elite rowers achieve intended intensities without external guidance remains unknown. The Purpose was to compare self-paced and HR-guided on-water rowing across three low intensity zones in elite rowers.

Methods

Fifteen national team rowers (7 female) completed an incremental step and ramp test on a rowing ergometer to determine the first lactate threshold (LT1, 1st rise) as a proxy for MT1, and V̇O₂max. Each rower then performed four on-water trials in the single scull (two self-paced, two HR-guided, each on a different day), each comprising six 15-minute steps targeting VeryLow, Low, and Moderate intensities in ascending and descending order. During self-paced trials, rowers relied on self-regulation. During HR-guided trials, they received real-time HR feedback and were advised to stay within 60–72%, 72–79%, and 79–82%HR_max for VeryLow, Low, and Moderate, respectively. HR, %V̇O₂max,  blood lactate (BLa), and rating of perceived exertion (RPE) were recorded. Differences between zones, guidance modes, and deviations from LT1 were analysed via linear mixed models. Sex was not modelled, as sex differences occurred only for absolute V̇O₂max, not for the relative intensity variables analysed.

Results

Across all zones, self-paced rowing elicited significantly higher %HR_max and %V̇O₂max than HR-guided rowing (all p < 0.01; Figure 1). Relative to LT1, VeryLow was significantly below LT1 in both modes, whereas Low did not differ significantly from LT1 in either condition. %HRmax at self-paced Low was not significantly different from HR-guided Moderate, indicating that self-paced Low intervals were performed at Moderate intensities. At Moderate intensity, mean values exceeded LT1 in both modes, but the deviation was markedly larger during self-paced rowing. Standard deviations for %HR_max and %V̇O₂max were consistently smaller when HR-guided. BLa did not distinguish VeryLow from Low (self-paced 1.2 ±0.3 vs. 1.2 ±0.4; HR-guided 1.1 ±0.3 vs. 1.1 ±0.3 mmol·L⁻¹). RPE increased across zones (self-paced 1.8 ±0.8 → 3.3 ±0.8 → 5.1 ±1.0) but did not significantly differ between modes.

Discussion

Self-paced rowing systematically resulted in higher and more variable intensities, particularly in Low, which overlapped with Moderate. Because BLa and RPE did not separate the guidance modes, HR appears most suitable for everyday intensity control.

Conclusion

HR-guidance improved adherence to the intended zones and reduced variability compared with self-paced rowing. However, fixed %HRmax targets did not consistently keep low-intensity rowing below LT1: even HR-guided, Low was not significantly different from LT1, and self-paced Low reached Moderate intensity. If the goal is to keep low-intensity training below LT1, prescription should be anchored to the individual LT1 rather than to fixed %HRmax cut-offs.

References

Bishop, D. J., Beck, B., Biddle, S. J. H., Denay, K. L., Ferri, A., Gibala, M. J., Headley, S., Jones, A. M., Jung, M., Lee, M. J., Moholdt, T., Newton, R. U., Nimphius, S., Pescatello, L. S., Saner, N. J., & Tzarimas, C. (2025). Physical activity and exercise intensity terminology: A joint American College of Sports Medicine (ACSM) expert statement and Exercise and Sport Science Australia (ESSA) consensus statement. Medicine & Science in Sports & Exercise, 57, 2599–2613. https://doi.org/10.1249/MSS.0000000000003795

Rosenblat, M. A., Watt, J. A., Arnold, J. I., Treff, G., Sandbakk, Ø. B., Esteve-Lanao, J., Festa, L., Filipas, L., Galloway, S. D., Muñoz, I., Ramos-Campo, D. J., Schneeweiss, P., Sellés-Pérez, S., Stöggl, T., Talsnes, R. K., Zinner, C., & Seiler, S. (2025). Which training intensity distribution intervention will produce the greatest improvements in maximal oxygen uptake and time-trial performance in endurance athletes? A systematic review and network meta-analysis of individual participant data. Sports Medicine, 55, 655–673. https://doi.org/10.1007/s40279-024-02149-3