Author(s): HOSSEINI, Z., OKTAVIUS, K., HU, K., GAO, P., JAMES, C., Institution: POINT FIT TECHNOLOGY LTD., Country: HONG KONG, Abstract-ID: 1847

INTRODUCTION:
Monitoring blood lactate (BL) concentration is a cornerstone of physiological profiling and training prescription in sports science. Conventional capillary sampling is invasive and provides only discrete data points, whereas wearable sweat-sensing technologies offer a non-invasive, continuous alternative. However, the physiological relevance and temporal dynamics of sweat lactate (SL) are not yet fully understood. This pilot study investigated the feasibility and temporal alignment of a novel wearable SL sensor, integrated onto an ultra-thin, conformable nanofilm, compared to gold-standard BL measurements during incremental cycling exercise.
METHODS:
Eight recreational cyclists (4 males, 4 females) performed an incremental cycling protocol under controlled laboratory conditions (25°C, 50%RH). The protocol commenced at 60 W, with workload increased by 20 W every 4 min until volitional exhaustion. Cadence was maintained at 80 rpm. Continuous SL was captured via an electrochemical sensor integrated onto a porous ultra-high-molecular-weight polyethylene (UHMWPE) nanofilm at the mid-anterior forearm [1]. BL was obtained during the final 10s of each 4-min stage. Data were normalized via min-max scaling, and a cross-correlation optimization algorithm (grid search: 0 to 1200s, 10s resolution) was employed to identify the maximal phase-coupling between systemic production and dermal secretion.
RESULTS:
In this pilot cohort (N=8), SL and BL profiles demonstrated strong temporal coupling. Raw data showed a mean Pearson correlation of 0.85±0.13, the correlation increased to 0.94 ± 0.03 after individualized temporal alignment. Analysis of physiological transport revealed a median lag of 65s (IQR: 155s), indicating substantial inter-individual differences in lactate transport and secretion kinetics.
CONCLUSION:
Preliminary findings support the feasibility of continuous SL monitoring during incremental exercise. While SL closely tracks systemic lactate dynamics following individualized temporal adjustment, pronounced variability in physiological lag suggests that personalized calibration strategies are necessary. Larger cohorts are required to determine whether SL monitoring can reliably inform real-time metabolic threshold detection.

[1] A. K. Oktavius et al., "Fully-Conformable Porous Polyethylene Nanofilm Sweat Sensor for Sports Fatigue," IEEE Sensors Journal, 21, 7, 8861-8867, 2021.