Sweat Production During Continuous and Interval Aerobic Exercise.

INTRODUCTION:Aerobic exercise within the habitable volume of small spacecraft needed for space exploration beyond low Earth orbit is expected to challenge the capacity of environmental control systems. Moisture control is a primary concern. Crewmembers will contribute moisture to the cabin environment in the form of sweat while exercising. The effects of continuous aerobic exercise for improving and maintaining aerobic capacity is well characterized. Likewise, evidence suggests that high intensity interval exercise for shorter durations is also effective in building and maintaining aerobic capacity.METHODS: On separate days, measures of sweat and respiratory responses were made for continuous (30 min of steady state exercise at ∼75% of aerobic capacity) and two interval (4 × 4 min, 8 × 30 s) exercise protocols.RESULTS: We observed that the 4-min and 30-s interval protocols produce 16% and 66% less metabolic water loss vs. the continuous exercise protocol, respectively. These responses were highly correlated with the amount of work performed (R² = 0.81) and the amount of energy expenditure (R² = 0.83) during exercise.DISCUSSION: These results suggest that interval exercise may be a useful alternative to continuous aerobic exercise when metabolic water production is an environmental concern. The results may inform the choices of aerobic exercise countermeasure protocols for use in deep space exploration.Ryder JW, Crowell JB, Song HJ, Ewert M. Sweat production during continuous and interval aerobic exercise. Aerosp Med Hum Perform. 2023; 94(8):623-628.

A novel approach for establishing fitness standards for occupational task performance.

PURPOSE: To identify strength and performance thresholds below which task performance is impaired. METHODS: A new weighted suit system was used to manipulate strength-to-body-weight ratio during the performance of simulated space explorations tasks. Statistical models were used to evaluate various measures of muscle strength and performance on their ability to predict the probability that subjects could complete the tasks in an acceptable amount of time. Thresholds were defined as the point of greatest change in probability per change in the predictor variable. For each task, median time was used to define the boundary between "acceptable" and "unacceptable" completion times. RESULTS: Fitness thresholds for four space explorations tasks were identified using 23 physiological input variables. Area under receiver operator characteristic curves varied from a low of 0.68 to a high of 0.92. CONCLUSION: An experimental analog for altering strength-to-body weight combined with a probability-based statistical model for success was suitable for identifying thresholds for task performance below which tasks could either not be completed or time to completion was unacceptably high. These results provide data for strength recommendations for exploration mission ambulatory task performance. Furthermore, the approach can be used to identify thresholds for other areas where occupationally relevant tasks vary considerably.

Isometric Midthigh Pull Reliability and Relationship to Deadlift One Repetition Maximum.

De Witt, JK, English, KL, Crowell, JB, Kalogera, KL, Guilliams, ME, Nieschwitz, BE, Hanson, AM, and Ploutz-Snyder, LL. Isometric midthigh pull reliability and relationship to deadlift one repetition maximum. J Strength Cond Res 32(2): 528-533, 2018-The purpose of this investigation was to examine the reliability of the isometric midthigh pull (IMTP) and the relationship between IMTP peak force and deadlift 1 repetition maximum (1RM). Nine subjects (5 men and 4 women; 40.6 ± 8.0 years; 1.72 ± 0.10 m; 75.6 ± 13.4 kg) participated in this study. Isometric midthigh pull and deadlift 1RM were both performed during 2 testing sessions. For IMTP, peak force and peak rate of force development (RFD) were determined, in addition to RFD at 30 ms, 50 ms, 90 ms, 150 ms, 200 ms, and 250 ms after initiation of the pull. Intraclass correlation coefficients (ICCs) were calculated to evaluate the reliability of IMTP measures. Pearson product-moment correlations and linear regression were used to determine associations between IMTP and deadlift 1RM. Isometric midthigh pull peak force was reproducible both within (ICC = 0.98 and 0.97) and between sessions (ICC = 0.89) and significantly correlated with deadlift 1RM (r = 0.88, p ≤ 0.05), but intermediate force outputs and RFD were not. Lack of associations between RFD and deadlift 1RM indicate that the ability to create explosive force may be independent of the ability to create maximal force. The strong relationship between IMTP peak force and deadlift 1RM was present regardless of which IMTP repetition across the 2 sessions was examined. Peak force generated during IMTP is a reliable method to assess full body maximal strength. A single IMTP repetition, provided adequate familiarization and warm-up, correlates strongly with deadlift 1RM. Practitioners can use the IMTP test as a method to estimate maximal deadlift strength in a quick and potentially less provocative manner than traditional 1RM testing.