# Ventilatory Efficiency and End-Tidal CO2 Kinetics During Active Recovery Following VT2—Referenced Intermittent Exercise in Basketball

## TL;DR

This study examines how basketball players recover during short active breaks after intense exercise, using a new testing method to better understand their performance dynamics.

## Contribution

A novel VT2-referenced progressive–intermittent treadmill protocol is introduced to assess recovery kinetics in basketball players.

## Key findings

- VO2 varied significantly across successive exercise bouts, indicating changing effort tolerance.
- PetCO2 showed a small downward trend during repeated exercise-recovery cycles.
- Peak performance metrics correlated with recovery slopes during different recovery phases.

## Abstract

Backround and Objectives: Basketball performance is shaped by repeated high-intensity actions interspersed with brief recovery. Conventional continuous or strictly incremental testing may not fully capture short active-recovery dynamics relevant to stop-and-go sports. Material and Methods: This study applied a VT2-referenced progressive–intermittent treadmill protocol and focused on 60-s active-recovery kinetics to describe effort tolerance in an applied basketball setting. Basketball players from Mureș County completed anthropometry (24 h pre-test, fasted) and a single laboratory visit. Pre-test training and diet were standardized for 48 h (submaximal training; predominantly carbohydrate intake). CPET was performed in 3-min stages (6.5 km·h−1 start; +0.7 km·h−1 per stage) and stopped at RER = 1.00 and/or blood lactate = 4.0 mmol·L−1 (operational VT2). After 3 min active recovery, participants completed six 60-s high-speed bouts separated by 60-s active recovery intervals (AR1–AR6), with intensities prescribed at 120–180% of VT2-derived speed, followed by an 8-min active recovery. For each AR interval, linear regression over 0–60 s yielded slopes for VO2, VO2/HR, VCO2, V̇E, VE/VO2, VE/VCO2, and PetCO2. Results: VT1 was determined at 2.29 m·s−1 (VO2 32 mL·min−1·kg−1) and VT2 at 3.07 m·s−1 (VO2 42 mL·min−1·kg−1). Maximal intermittent speed was 5.33 m·s−1 (VO2 45.5 mL·min−1·kg−1; RER 1.06; PetCO2 38 mmHg). VO2 differed across successive bouts (p = 0.0001), while PetCO2 showed a small downward drift across repetitions. Peak indices (max speed, VE/VCO2max, PetCO2max, VEmax) were associated with phase-specific recovery slopes across early, mid, and late recovery periods (false discovery rate–adjusted correlations). Lactate decreased over 8 min, but lactate change rates were not associated with peak indices. Conclusions: The VT2-referenced progressive–intermittent protocol appears feasible in basketball players and provides phase-dependent recovery information that complements conventional peak CPET outcomes, with potential relevance for applied team settings.