Livio Zerbini

Anaerobic threshold assessment through the ventilatory method during roller-ski skating testing: right or wrong?

Fabre, N, Bortolan, L, Pellegrini, B, Zerbini, L, Mourot, L, and Schena, F. Anaerobic threshold assessment through the ventilatory method during roller-ski skating testing: right or wrong? J Strength Cond Res 26(2): 381–387, 2012—This study aimed at questioning the validity of the ventilatory method to determine the anaerobic threshold (respiratory compensation point [RCP]) during an incremental roller-ski skating test to exhaustion. Nine elite crosscountry skiers were evaluated. The skiers carried out an incremental roller-ski test on a treadmill with the V2 skating technique. Ventilatory parameters were continuously collected breath by breath, thanks to a portable gas exchange measurement system. Poling signal was obtained using instrumented ski poles. For each stage, ventilatory and poling signals were synchronized and averaged. The poor coefficient of interobserver reliability for the time at RCP confirmed the great difficulty felt by the 3 blinded reviewers for the RCP determination. Moreover, the reviewer agreed with the impossibility of determining RCP in 4 of the 9 skiers. There was no significant difference between breathing frequency (Bf) and poling frequency (Pf) during the last 8 stages. However, it seems that the differences observed during the first stages arose from the use of either a strictly 1:1 or a 1:2 Bf to Pf ratio when the exercise intensity was still moderate. So, even if there were significant differences between the frequencies, the Bf was strictly subordinate to the Pf during the entire test. In the same way, the normalized tidal volume and peak poling forces curves were superposable. These findings showed that when the upper body is mainly involved in the propulsion, the determinants of the ventilation are strictly dependent on the poling pattern during an incremental test to exhaustion. Thus, during roller-ski skating, the determination of RCP must be used cautiously because too much depending on mechanical factors.

Physiological and perceptual responses to nordic walking in a natural mountain environment

Background: Interest around Nordic Walking (NW) has increased in recent years. However, direct comparisons of NW with normal walking (W), particularly in ecologically valid environments is lacking. The aim of our study was to compare NW and W, over long distances in a natural mountain environment. Methods: Twenty one subjects (13 male/8 female, aged 41 ± 12 years, body mass index BMI 24.1 ± 3.7), walked three distinct uphill paths (length 2.2/3.4/7 km) with (NW) or without (W) walking poles over two separate days. Heart rate (HR), energy expenditure (EE), step length (SL), walking speed (WS), total steps number (SN) and rating of perceived exertion (RPE) were monitored. Results: HR (+18%) and EE (+20%) were higher in NW than in W whilst RPE was similar. SN (−12%) was lower and SL (+15%) longer in NW. WS was higher (1.64 vs. 1.53 m s−1) in NW. Conclusions: Our data confirm that, similarly to previous laboratory studies, differences in a range of walking variables are present between NW and W when performed in a natural environment. NW appears to increase EE compared to W, despite a similar RPE. Thus, NW could be a useful as aerobic training modality for weight control and cardiorespiratory fitness.

Effects of acute hypoxia on the oxygen uptake kinetics of older adults during cycling exercise.

Pulmonary oxygen uptake, heart rate (HR), and deoxyhemoglobin (HHb) kinetics were studied in a group of older adults exercising in hypoxic conditions. Fourteen healthy older adults (aged 66 ± 6 years) performed 4 exercise sessions that consisted of (i) an incremental test to exhaustion on a cycloergometer while breathing normoxic room air (fractional inspired oxygen (FiO(2)) = 20.9% O(2)); (ii) an incremental test to exhaustion on a cycloergometer while breathing hypoxic room air (FiO(2) = 15% O(2)); (iii) 3 repeated square wave cycling exercises at moderate intensity while breathing normoxic room air; and (iv) 3 repeated square wave cycling exercises at moderate intensity while breathing hypoxic room air. During all exercise sessions, pulmonary gas exchange was measured breath-by-breath; HHb was determined on the vastus lateralis muscle by near-infrared spectroscopy; and HR was collected beat-by-beat. The pulomary oxygen uptake kinetics became slower in hypoxia (31 ± 9 s) than in normoxia (27 ± 7 s) because of an increased mismatching between O(2) delivery to O(2) utilization at the level of the muscle. The HR and HHb kinetics did not change between hypoxia and normoxia.

VO2p, HR and HHb kinetics in young and older adults during cycling 1 in acute hypoxia

Abstract The adjustment of pulmonary oxygen uptake (VO2p), heart rate (HR), and muscle deoxygenation [HHb] were examined during the transition to moderate-intensity cycling exercise, in eight older adults (70 ± 2 years) and eight young adults (29 ± 4 years) under 2 conditions: normoxia (FIO2=20.9%) and hypoxia (FIO2=15%). The subjects performed repeated step transitions from an active baseline (12 W) to a relative power output (80% VO2 of the first ventilatory threshold) in both conditions. Phase 2 VO2p, HR, and HHb data were fit with an exponential model. For both groups slower phase 2 VO2p kinetics, were found in hypoxia compared to normoxia (34±8 vs 29±6 sec for older adults and 25±4 vs 19±4 sec for young adults). Only the young adult group showed greater HR (33±6 vs 19±4 sec), [HHb] (18±3 vs 15±2 sec) and (24±2 vs 22±2 sec) in hypoxia compared to normoxia, whereas only the older adults group exhibited a greater [HHb]/VO2 (1.13±0.1 vs 1.09±0.1) ratio in hypoxia compared to normoxia. These findings support the idea that, for older adults the main constrain to the VO2p kinetics in hypoxia lies in the microvascular O2 delivery, whereas for young adults factors other than the microvascular O2 delivery (i.e slowed mitochondrial respiration) are responsible for the slowed VO2p kinetics in hypoxia.

Retraction: VO2p, HR and HHb kinetics in young and older adults during cycling in acute hypoxia

Dr. Terry Graham, the Editor of Applied Physiology, Nutrition, and Metabolism (APNM), after communication with the corresponding author of the paper (VO2p, HR and HHb kinetics in young and older adults during cycling in acute hypoxia), is retracting the paper from APNM, given its substantial overlap with a paper published previously elsewhere. Note that the paper being retracted was published only in the electronic version of APNM as a Just-IN manuscript; it was not incorporated into a print issue.