Jesse A. Goodrich

Haemoglobin mass alterations in healthy humans following four‐day head‐down tilt bed rest

What is the central question of this study? Is haemoglobin mass (Hbmass) decreased following 4 days of head‐down tilt bed rest (HDTBR), and does increased red blood cell (RBC) destruction mediate this adaptation? What is the main finding and its importance? Haemoglobin mass was increased immediately following HDTBR, before decreasing below baseline 5 days after return to normal living conditions. The transient increase in Hbmass might be the result of decreased RBC destruction, but it is also possible that spleen contraction after HDTBR contributed to this adaptation. Our data suggest that the decreased Hbmass 5 days following HDTBR resulted from decreased RBC production, not increased RBC destruction.

Hip Distraction Without a Perineal Post: A Prospective Study of 1000 Hip Arthroscopy Cases:

Background: Hip arthroscopy has traditionally been performed with a perineal post, resulting in various groin-related complications, including pudendal nerve neurapraxias, vaginal tears, and scrotal necrosis. Purpose: To assess the safety of a technique for hip distraction without the use of a perineal post. Study Design: Case series; Level of evidence, 4. Methods: We prospectively analyzed a consecutive cohort of 1000 hips presenting to a dedicated hip preservation clinic; all patients had hip pain and were subsequently treated with hip arthroscopy. Demographic variables, hip pathology, and lateral center edge angle were recorded for each case. In the operating room, the patient’s feet were placed in traction boots in a specifically designed distraction setup, and the operative table was placed in varying degrees of Trendelenburg. With this technique, enough resistance is created by gravity and friction between the patient’s body and the bed to allow for successful hip distraction without the need for a perineal post. In a subset of 309 hips (n = 281 patients), the degrees of Trendelenburg as well as the distraction force were analyzed. Results: The mean ± SD Trendelenburg angle used among the subset of 309 hips was 11° ± 2°. The mean initial distraction force necessary was 90 ± 28 lb, which decreased to 65 ± 24 lb by 30 minutes after traction initiation (P < .0001). The most important variables in determining initial force for this cohort of patients were, in order of magnitude, sex (P < .0001), weight (P < .0001), and lateral center edge angle (P < .01). No groin-related complications occurred among the entire cohort of patients, including soft tissue or nerve-related complications. The rate of deep venous thrombosis was 2 in 1000. Conclusion: The use of the Trendelenburg position and a specially designed distraction setup during hip arthroscopy allows for safe hip distraction without a perineal post, thereby eliminating groin-related soft tissue and nerve complications. Certain patient variables can be used to estimate the required distraction force and inclination angle with this method.

Ten Days of Intermittent, Low-dose Carbon Monoxide Inhalation does not Significantly Alter Hemoglobin Mass, Aerobic Performance Predictors, or Peak-power Exercise Tolerance

Carbon monoxide (CO) rebreathing procedures are used to assess hemoglobin mass (Hbmass) but recent evidence suggests that CO is a signaling molecule that may alter physiological functions. We examined the effects of 10 days of intermittent, low-dose CO inhalation on Hbmass, aerobic performance predictors, and peak-power exercise tolerance. 18 recreationally-active men were randomized to either CO or placebo inhalation groups in a single-blind, pre-post parallel-groups trial. Primary outcomes were assessed before and after an intervention period during which subjects inhaled a bolus of 1.2 ml kg(-1) CO or placebo (room air) for 30 s, once per day on 10 days over a 12-day period. Cycling tests were performed >16 h following CO inhalation to exclude acute effects of CO exposure. CO inhalation elevated carboxyhemoglobin by 4.4±0.4% (mean±SD) following each exposure. Compared to placebo, chronic CO inhalation did not significantly alter Hbmass (p=0.99), peak oxygen uptake (p=0.59), peak power output (p=0.10), submaximal oxygen uptake (p=0.91), submaximal RER (p=0.22), lactate threshold (p=0.65), or peak-power exercise tolerance (p=0.60). In conclusion, our data support the ability to perform repeated measurements of Hbmass using CO rebreathing over a 12-day period without altering physiological responses.

The Influence of Oxygen Saturation on the Relationship Between Hemoglobin Mass and VO2max

Hemoglobin mass (tHb) is a key determinant of maximal oxygen uptake (VO 2 max). We examined whether oxyhemoglobin desaturation (ΔS a O 2 ) at VO 2 max modifies the relationship between tHb and VO 2 max at moderate altitude (1,625 m). Seventeen female and 16 male competitive, endurance-trained moderate-altitude residents performed two tHb assessments and two graded exercise tests on a cycle ergometer to determine VO 2 max and ΔS a O 2 . In males and females respectively, VO 2 max (ml·kg −1 ·min −1 ) ranged from 62.5–83.0 and 44.5–67.3; tHb (g·kg −1 ) ranged from 12.1–17.5 and 9.1–13.0; and S a O 2 at VO 2 max (%) ranged from 81.7–94.0 and 85.7–95.0. tHb was related to VO 2 max when expressed in absolute terms and after correcting for body mass (r=0.94 and 0.86, respectively); correcting by ΔS a O 2 did not improve these relationships (r=0.93 and 0.83). Additionally, there was a negative relationship between tHb and S a O 2 at VO 2 max (r=–0.57). In conclusion, across a range of endurance athletes at moderate altitude, the relationship between tHb and VO 2 max was found to be similar to that observed at sea level. However, correcting tHb by ΔS a O 2 did not explain additional variability in VO 2 max despite significant variability in ΔS a O 2 ; this raises the possibility that tHb and exercise-induced ΔS a O 2 are not independent in endurance athletes.

The Effects of Cooling during Constant Power Non-steady State Cycling in Endurance Trained Athletes: 2020 Board #172 June 2, 2: 00 PM - 3: 30 PM.

PURPOSE: The aim of this study was to compare the effects of different cooling methods on thermoregulatory and energetic responses during constant power, non-steady state cycling in thermoneutral conditions. METHODS: Endurance trained males (n = 12) performed a graded exercise test to determine lactate threshold power (1 mM above baseline). On three separate days, subjects cycled at their lactate threshold power for 60 min or until volitional exhaustion under three conditions: wearing a water perfused vest and sleeves circulating icecooled water (COOL), a synthetic shirt embedded with an active particle technology claimed to facilitate evaporative heat loss (EVAP), and a standard synthetic shirt (CON). Metabolic variables, core temperature (TC), sweat rate, thermal sensation, and rating of perceived exertion (RPE) were measured during testing. RESULTS: A greater percent of subjects completed 60 min of cycling during COOL (82%) and EVAP (75%) compared to CON (64%). The increase in TC from baseline at isotime (same time point across conditions based on the shortest duration completed in all three experimental conditions specific to each subject) was reduced during COOL and EVAP compared to CON (1.44 ± 0.45 and 1.52 ± 0.43 vs. 1.66 ± 0.45 °C, p < 0.05). Sweat rate was reduced during COOL compared to EVAP and CON (1,312 ± 331 vs. 1,525 ± 393 and 1,550 ± 548 mL·hr -1 , p < 0.01). Gross efficiency decreased over time from baseline in all conditions (p < 0.01), but COOL attenuated this decrease by 22% compared to CON (p < 0.05). No differences in the change in gross efficiency over time were found between COOL and EVAP or between EVAP and CON. Over time, thermal sensation was reduced by 23% during COOL compared to EVAP and CON (p < 0.01), whereas RPE was reduced by 3% and 2% during COOL and EVAP compared to CON (p < 0.01). CONCLUSION: During constant power, non-steady state cycling, cooling using the vest and sleeves or the synthetic shirt embedded with an active particle technology blunted the rise in core temperature and RPE over time compared to the standard synthetic shirt. Cooling using the vest and sleeves also reduced the decrease in gross efficiency over time as well as reduced sweat rate and thermal sensation compared to wearing the standard synthetic shirt. Supported by a donation from 37.5 Technology.

Beneficial Effects of Cooling during Constant Power Non-steady State Cycling

This study compared the effects of cooling on the energetic and associated physiological and perceptual responses to constant power, non-steady state cycling. Twelve males cycled at their lactate threshold power for 60 min or until exhaustion under 3 conditions: wearing a cooling vest and sleeves (COOL), a synthetic shirt embedded with an active particle technology claimed to facilitate evaporative heat loss (EVAP), and a standard synthetic shirt (CON). When adjusted for time, the increase in gastrointestinal temperature from baseline was reduced during COOL and EVAP compared to CON (1.44±0.45 and 1.52±0.43 vs. 1.66±0.45°C, p<0.05). Sweat rate was reduced during COOL compared to EVAP and CON (1 312±331 vs. 1 525±393 and 1 550±548 mL·h-1, p<0.01). Gross efficiency decreased over time across conditions (p<0.01), but COOL attenuated this decrease by 22% compared to CON (p<0.05). The rating of perceived exertion was reduced during COOL and EVAP compared to CON (p<0.01). In conclusion, cooling using a vest and sleeves or wearing an active particle technology shirt reduced the rise in gastrointestinal temperature and rating of perceived exertion compared to a standard synthetic shirt. Cooling using a vest and sleeves also reduced the decrease in gross efficiency and sweat rate compared to wearing the standard synthetic shirt.