Physiological and perceptual responses to exercise and cold stress with special reference to climatic and textile factors

The primary objective of the first three studies was to provide an indirect assessment of the properties of garments designed for wear in cold environments using human trials. The study design incorporated a specific protocol that allowed for evaluation of specific garment properties, based on physiological and subjective responses. Based on some interesting trends in VO2 response that were noted in the earlier studies, the fourth study aimed to determine the effects of cooling on the VO2 response to exercise in moderate and heavy intensity domains. The first two studies compared the performance of three garments that differed in the degree to which they were air-permeable: high (HP), medium (MP) and low (LP) permeability. The studies were conducted in two sub-zero environmental temperatures, against a constant wind speed. The protocol consisted of a 30 min rest period followed by 30 min of brisk walking on an inclined treadmill. The results suggest that HP was the least favourable garment in the imposed conditions, based on higher values for rating of cold perception (RPC) and elevated VO2 (indicating a more marked shivering response). Furthermore, it appeared that MP was the most effective of the suits, despite having a greater air permeability than LP. This indicates that factors other than wind resistance properties may have a significant effect on garment performance in this particular environment, taking into consideration duration of exposure, ambient temperature, wind-speed and physical activity status. The third study compared the wicking capacity of four garments (polyamide/nylon, capilene polyester, polyester and cotton), designed for wear as a base-layer, that varied in their physical properties and physical characteristics. It is recognised that evaporation of sweat taking place after cessation of exercise in the cold will cool the body, during a period where heat preservation is especially important. The design of the present study incorporated a 20 min exercise period, followed by a subsequent 45 min rest period in cool environment (1° C), during which the garments were evaluated. Lower RPC values and a tendency for a lower VO2 during rest, indicated that the polyester garment, which combined good wicking qualities with a high thermal resistance, was superior to the other garments in its capacity at offsetting heat loss. The results do not imply that heat transfer was prevented by the favourable garment, but rather that it was diminished in magnitude. The principal aim of the final study was to investigate the influence of body cooling on the VO2 response to exercise above and below the lactate threshold, employing square-wave cycle-ergometer exercise transitions for the two intensity domains. The design also allowed for determination of the influence of sub-normal temperatures on incremental cycling performance. The results showed that the induced cooling had detrimental effects on maximal aerobic performance. VO2 during moderate constant-load exercise was significantly elevated following cooling; a similar effect, however, was observed only during the initial stages of heavy intensity constant-load exercise. Furthermore, the characteristic VO2 slow-component observed during constant-load exercise above the lactate threshold remained unaltered by sub-normal temperatures. The results suggest that a graded suppression of shivering occurs with increasing exercise intensity. Furthermore, the findings indicate that temperature is likely to contribute to the slow-component of VO2 by only a trivial amount

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

The effects of creatine supplementation on cardiovascular, metabolic, and thermoregulatory responses during exercise in the heat in endurance-trained humans.

The effects of creatine (Cr) supplementation on cardiovascular, metabolic, and thermoregulatory responses, and on the capacity of trained humans to perform prolonged exercise in the heat was examined. Endurance-trained males (n = 21) performed 2 constant-load exercise tests to exhaustion at 63 ± 5 % VO in the heat (ambient temperature: 30.3 ± 0.5 °C) before and after 7 d of Cr (20 g × d-1 Cr + 140 g × d-1 glucose polymer) or placebo. Cr increased intracellular water and reduced thermoregulatory and cardiovascular responses (e.g., heart rate, rectal temperature, sweat rate) but did not significantly increase time to exhaustion (47.0 ± 4.7 min vs. 49.7 ± 7.5 min, P = 0.095). Time to exhaustion was increased significantly in subjects whose estimated intramuscular Cr levels were substantially increased (“responders”: 47.3 ± 4.9 min vs. 51.7 ± 7.4 min, P = 0.031). Cr-induced hyperhydration can result in a more efficient thermoregulatory response during prolonged exercise in the heat

Y chromosome haplogroups of elite Ethiopian endurance runners

Favourable genetic endowment has been proposed as part of the explanation for the success of East African endurance athletes, but no evidence has yet been presented. The Y chromosome haplogroup distribution of elite Ethiopian athletes (n=62) was compared with that of the general Ethiopian population (n=95) and a control group from Arsi (a region producing a disproportionate number of athletes; n=85). Athletes belonged to three groups: marathon runners (M; n=23), 5–km to 10–km runners (5–10K; n=21) and other track and field athletes (TF; n=18). DNA was extracted from buccal swabs and haplogroups were assigned after the typing of binary markers in multiplexed minisequencing reactions. Frequency differences between groups were assessed by using contingency exact tests and showed that Y chromosome haplogroups are not distributed amongst elite Ethiopian endurance runners in the same proportions as in the general population, with statistically significant (P less than 0.05) differences being found in four of the individual haplogroups. The geographical origins and languages of the athletes and controls suggest that these differences are less likely to be a reflection of population structure and that Y chromosome haplogroups may play a significant role in determining Ethiopian endurance running success