Thoraco-abdominal coordination and performance during uphill running at altitude.

INTRODUCTION: Running races on mountain trails at moderate-high altitude with large elevation changes throughout has become increasingly popular. During exercise at altitude, ventilatory demands increase due to the combined effects of exercise and hypoxia. AIM: To investigate the relationships between thoraco-abdominal coordination, ventilatory pattern, oxygen saturation (SpO2), and endurance performance in runners during high-intensity uphill exercise. METHODS: Fifteen participants (13 males, mean age 42±9 yrs) ran a "Vertical Kilometer," i.e., an uphill run involving a climb of approximately 1000 m with a slope greater than 30%. The athletes were equipped with a portable respiratory inductive plethysmography system, a finger pulse oximeter and a global positioning unit (GPS). The ventilatory pattern (ventilation (VE), tidal volume (VT), respiratory rate (RR), and VE/VT ratio), thoraco-abdominal coordination, which is represented by the phase angle (PhA), and SpO2 were evaluated at rest and during the run. Before and after the run, we assessed respiratory function, respiratory muscle strength and the occurrence of interstitial pulmonary edema by thoracic ultrasound. RESULTS: Two subjects were excluded from the respiratory inductive plethysmography analysis due to motion artifacts. A quadratic relationship between the slope and the PhA was observed (r = 0.995, p = 0.036). When the slope increased above 30%, the PhA increased, indicating a reduction in thoraco-abdominal coordination. The reduced thoraco-abdominal coordination was significantly related to reduced breathing efficiency (i.e., an increased VE/VT ratio; r = 0.961, p = 0.038) and SpO2 (r = -0.697, p<0.001). Lower SpO2 values were associated with lower speeds at 20%≥slope≤40% (r = 0.335, p<0.001 for horizontal and r = 0.36, p<0.001 for vertical). The reduced thoraco-abdominal coordination and consequent reduction in SpO2 were associated with interstitial pulmonary edema. CONCLUSION: Reductions in thoraco-abdominal coordination are associated with a less efficient ventilatory pattern and lower SpO2 during uphill running. This fact could have a negative effect on performance.

Residence at Moderate Versus Low Altitude Is Effective at Maintaining Higher Oxygen Saturation During Exercise and Reducing Acute Mountain Sickness Following Fast Ascent to 4559 m.

OBJECTIVE: To continuously monitor oxygen saturation (SpO2) by pulse oximeter and assess the development of acute mountain sickness (AMS) using the Lake Louise Score (LLS) during ascent from 1154 to 4559 m in 2 groups of subjects: 10 moderate-altitude residents (MAR; ≥1000-≤2500 m) and 34 low-altitude residents (LAR). MAR are reported to have a lower incidence of AMS during ascent to higher altitudes compared with LAR. Whether this is related to higher SpO2 is still open to debate. METHODS: Seventy subjects were recruited; 24-hour SpO2 monitoring with finger pulse oximetry was performed. All subjects rode a cable car from 1154 to 3275 m and then climbed to 3647 m, where 60 subjects (LAR) overnighted. The second day, 34/60 LAR reached the highest altitude. Ten subjects who lived permanently at 1100 to 1400 m (MAR) climbed directly to 4559 m without an overnight stop. RESULTS: One LAR was excluded from the analysis because he performed a preacclimatization. We compared data of 10 MAR with data of 33 LAR who reached 4559 m. Two MAR had an LLS of 3, and 8 scored <3. Six LAR had an LLS of 3 to 4, 8 scored ≥5, and 19 scored <3. SpO2 monitoring showed higher mean SpO2 in MAR during ascent above 3600 m compared with LAR (MAR, 79±4% vs LAR, 76±5%; analysis of variance, P = .03). CONCLUSIONS: The results of this preliminary study suggest that residence at moderate altitude allows maintenance of higher SpO2 and reduces risk of developing AMS during rapid ascent to higher altitude.

Long-term monitoring of oxygen saturation at altitude can be useful in predicting the subsequent development of moderate-to-severe acute mountain sickness.

OBJECTIVE: The use of pulse oximetry (Spo2) to identify subjects susceptible to acute mountain sickness (AMS) is the subject of debate. To obtain more reliable data, we monitored Spo2 for 24 hours at altitude to investigate the ability to predict impending AMS. METHODS: The study was conducted during the climb from Alagna (1154 m) to Capanna Regina Margherita (4559 m), with an overnight stay in Capanna Gnifetti (3647 m). Sixty subjects (11 women) were recruited. Each subject was fitted with a 24-hour recording finger pulse oximeter. The subjects rode a cable car to 3275 m and climbed to 3647 m, where they spent the night. RESULTS: In the morning, 24 subjects (6 women) had a Lake Louise Questionnaire score (LLS) ≥ 3 (AMS(+)), and 15 subjects (4 women) exhibited moderate-to-severe disease (LLS ≥ 5 = AMS(++)). At Alagna, Spo2 did not differ between the AMS(-) and AMS(+) subjects. At higher stations, all AMS(+) subjects exhibited a significantly lower Spo2 than did the AMS(-) subjects: at 3275 m, 85.4% vs 87.7%; resting at 3647 m, 84.5% vs 86.4%. The receiver operating characteristics curve analysis resulted in a rather poor discrimination between the AMS(-) subjects and all of the AMS(+) subjects. With the cutoff LLS ≥ 5, the sensitivity was 86.67%, the specificity was 82.25%, and the area under the curve was 0.88 (P < .0001) for Spo2 ≤ 84% at 3647 m. CONCLUSIONS: We conclude that AMS(+) subjects exhibit a more severe and prolonged oxygen desaturation than do AMS(-) subjects starting from the beginning of altitude exposure, but the predictive power of Spo2 is accurate only for AMS(++).

Inter-individual differences in control of alveolar capillary blood volume in exercise and hypoxia.

We compared by non-invasive technique the adaptive response of alveolar capillary network to edemagenic conditions (exercise and high altitude [HA, PIO2 107mmHg] in subjects with different resting sea level (SL) capillary blood volume (normalized to alveolar volume, Vc/Va): Group 1 (N=10, Vc/Va=16.1±6.8ml/L- mean±SD) and Group 2 (N=10, Vc/Va=25±7.7). In Group 1 Vc/Va remained unchanged in HA at rest and increased during exercise at SL (26.3±8.6) and HA (28.75±10.2); in Group 2 Vc/Va significantly decreased in HA (19±6) and did not increase in exercise at SL and HA. We hypothesize that Group2 exerts a tight control on Vc/Va being more exposed to the risk of lung edema due to inborn greater microvascular permeability. Conversely, Group 1 appears more resistant to lung edema given the large capillary recruitment in the most edemagenic condition. The 4-fold increase in frequency dependence of respiratory resistance in Group2 in HA stems for greater proneness for lung water perturbation compared to Group 1.

Periodic breathing, arterial oxyhemoglobin saturation, and heart rate during sleep at high altitude.

The aim of this study was to investigate the effects of acclimatization to high altitude on periodic breathing (PB), arterial oxygen saturation (Sao(2)), and heart rate (HR). Nine male elite climbers, age 24-52 years underwent overnight cardiorespiratory monitoring at sea level and at Everest North Base Camp (5180 m), during the first (BC1) and the tenth (BC2) nights. PB was commonplace in all subjects at high altitude. PB cycle duration increased (p<0.0001) from BC1 (21.7±1.9 s) to BC2 (26.7±2.1 s). Mean Sao(2) from BC1 to BC2, significantly increased during wakefulness (77.4±3.4% vs. 82.5±2.8%; p<0.001) and during sleep regular breathing (73.3±3.8% vs. 77.8±2.9%; p=0.022). During PB, mean higher Sao(2) was 75.3±3.6% at BC1 and 82.4±2.9% at BC2 (p<0.001); mean lower Sao(2) was 68.2±4.0% at BC1 and 74.5±4.3% at BC2 (p<0.01). During PB, mean higher HR was 72.4±8.8 b/min at BC1 and 63.3±6.0 b/min at BC2 (p<0.0002); mean lower HR were 53.6±7.5% at BC1 and 43.6±7.3% at BC2 (p<0.0001). The mean Sao(2) during PB compared with Sao(2) at night without PB was unchanged. Acclimatization to high altitude resulted in an overall increase in Sao(2) along with an increase in the PB cycle duration and a decrease in HR.

A simple method for home exercise training in patients with chronic obstructive pulmonary disease: one-year study.

PURPOSE: The success of long-term exercise training (ExT) programs resides in the integration between exercise prescription and patient compliance with home training. One of the crucial issues for the patients is the understanding of appropriate exercise intensity. We compared 2 methods of home ExT, based on walking. METHODS: Forty-seven patients with chronic obstructive pulmonary disease were recruited and underwent respiratory function, exercise capacity evaluation with a 6-minute walk test, and treadmill tests. Physical activity was monitored by a multisensor Armband (SenseWear, Body Media, Pittsburgh, PA). Patients were randomly assigned to 2 different home training methods and assessed again after 6 and 12 months; group A1: speed walking paced by a metronome, and group A2: walking a known distance in a fixed time. RESULTS: Thirty-six patients completed the study. All subjects showed a significant improvement in the 6-minute walk test after 1 year but the improvement was higher in A1 than in A2 (P < .05). Physical activity levels were significantly higher at T12 versus baseline only in group A1 (P < .05). CONCLUSIONS: The use of a metronome to maintain the rate of walking during home ExT seems to be beneficial, allowing patients to achieve and sustain the optimal exercise intensity, and resulting in greater improvement compared to simply using a fixed time interval exercise.