Short term microgravity effect on isometric hand grip and precision pinch force with visual and proprioceptive feedback

An Empirical and Subjective Model of Upper Extremity Fatigue Under Hypogravity

In the context of extra-terrestrial missions, the effects of hypogravity (0 < G < 1) on the human body can reduce the well-being of the crew, cause musculoskeletal problems and affect their ability to perform tasks, especially during long-term missions. To date, studies of the effects of hypogravity on human movement are limited to experiments on the lower limbs. Here, we extend the knowledge base to the upper limbs, by conducting experiments to evaluate the effect of hypogravity on upper limb physical fatigue and mental workload in participants. Our hypothesis was that hypogravity would both increase participant productivity, by reducing overall physical fatigue expressed in Endurance Time, and reduce mental workload. Task Intensity-Endurance time curves are developed especially in seated positions, while performing static, dynamic, repetitive tasks. This experiment involved 32 healthy participants without chronic problems of the musculoskeletal system aged 33.59 ± 8.16 years. Using the collected data, fatigue models were constructed for tasks of varying Intensity. In addition, all participants completed the NASA – Task Load Index subjective mental workload assessment, which revealed the level of subjective workload when executing different tasks. We found two trends in the empirical fatigue models associated with the difference between the strength capabilities of males and females. The first is a significant positive (p = 0.002) relation between Endurance time and gravity level (⅙ G Moon, ⅓ G Mars, 1G) with negative coefficient for males and females for a static task. And there is marginal relation (p < 0.1) between overall mental workload and gravity level with a positive coefficient for males and females for the same task. The same trend was observed for dynamic and repetitive tasks. We concluded that the Task Intensity-Endurance Time model, adapted to hypogravity in combination with subjective mental assessment, is useful to human fatigue investigation. The combination of these methods used for ergonomic analysis and digital human modeling, could improve worker productivity. Finally, this study may help prepare astronauts for long-term missions on the Moon and Mars and improve our understanding of how we can prevent musculoskeletal disorders caused by hazardous manual handling under such extreme environments.

Robot-assisted surgery in space: pros and cons. A review from the surgeon's point of view

The target of human flight in space has changed from permanence on the International Space Station to missions beyond low earth orbit and the Lunar Gateway for deep space exploration and Missions to Mars. Several conditions affecting space missions had to be considered: for example the effect of weightlessness and radiations on the human body, behavioral health decrements or communication latency, and consumable resupply. Telemedicine and telerobotic applications, robot-assisted surgery with some hints on experimental surgical procedures carried out in previous missions, had to be considered as well. The need for greater crew autonomy in health issues is related to the increasing severity of medical and surgical interventions that could occur in these missions, and the presence of a highly trained surgeon on board would be recommended. A surgical robot could be a valuable aid but only inasfar as it is provided with multiple functions, including the capability to perform certain procedures autonomously. Space missions in deep space or on other planets present new challenges for crew health. Providing a multi-function surgical robot is the new frontier. Research in this field shall be paving the way for the development of new structured plans for human health in space, as well as providing new suggestions for clinical applications on Earth.

Effects of Resting, Consecutive, Long-Duration Water Immersions on Neuromuscular Endurance in Well-Trained Males

Purpose: This study examined the effects of repeated long-duration water immersions (WI)s at 1.35 atmospheres absolute (ATA) on neuromuscular endurance performance. We hypothesized that, following 5 days of consecutive, resting, long-duration WIs, neuromuscular endurance performance would decrease.

Methods: Fifteen well-trained, male subjects completed five consecutive 6-h resting WIs with 18-h surface intervals during the dive week while breathing compressed air at 1.35 ATA. Skeletal muscle endurance performance was assessed before and after each WI, and 24 and 72 h after the final WI. Muscular endurance assessments included 40% maximum handgrip endurance (MHE) and 50-repetition maximal isokinetic knee extensions. Near infrared spectroscopy was used to measure muscle oxidative capacity of the vastus lateralis and localized muscle tissue oxygenation of the vastus lateralis and flexor carpi radialis. Simultaneously, brachioradialis neuromuscular activation was measured by surface electromyography.

Results: A 24.9% increase (p = 0.04) in the muscle oxidative capacity rate constant (k) occurred on WI 4 compared to baseline. No changes occurred in 40% MHE time to exhaustion or rate of fatigue or total work performed for the 50-repetition maximal isokinetic knee extension. The first quartile of deoxygenated hemoglobin concentration showed a 6 and 35% increase on WIs 3 and 5 (p = 0.026) with second quartile increases of 9 and 32% on WIs 3 and 5 (p = 0.049) during the 40% MHE testing when compared to WI 1.

Conclusion: Our specific WI protocol resulted in no change to muscular endurance and oxygen kinetics in load bearing and non-load bearing muscles.

Effects of repeated long-duration water immersions on skeletal muscle performance in well-trained male divers

PURPOSE

The objective of this study was to examine the effects of repeated long-duration water immersions (WI)s at 1.35 atmospheres absolute (ATA) on neuromuscular performance in load bearing and non-load bearing muscle groups.

METHODS

During a dive week (DW), fifteen well-trained male divers completed five consecutive 6-h resting dives with 18-h surface intervals while breathing compressed air at 1.35 ATA. Skeletal muscle performance assessments occurred immediately before and after each WI, and 24 and 72 h after the final WI. Exercise assessments included maximum voluntary isometric contraction (MVIC), maximal isokinetic (IK) contraction, maximum handgrip strength (MHG). Surface electromyography measured neuromuscular activation of the quadriceps, biceps brachii (BB), and brachioradialis.

RESULTS

MVIC torque of knee extensors and BB decreased by 6% (p = 0.001) and 2% (p = 0.014), respectively, by WI 3. Maximal IK torque of knee extensors increased by 11 and 5% post-WI on WIs 3 and 5 (p < 0.001) with greater neuromuscular activation post-WI than pre-WI (p < 0.001). Maximum IK elbow flexion torque did not change throughout the DW with BB neuromuscular activation greater post-WI than pre-WI (p < 0.001). MHG force output was 4% greater post-WI than pre-WI (p < 0.001) with increased brachioradialis activation through 72-h post-WI (p < 0.001). All muscle performance metrics returned baseline levels by 72-h post-WI.

CONCLUSION

Our findings indicate that repeated WIs caused noticeable decrements in neuromuscular activation and performance of load bearing muscles on WI 3 while full recovery was observed by 72-h post-WI.

Low-volume muscular endurance and strength training during 3-week forearm immobilization was effective in preventing functional deterioration

Purpose

The purpose of this study was to determine whether endurance and strength hand grip exercises during 3-week upper limb immobilization preserve muscle oxidative capacity, endurance performance and strength.

Methods

Ten healthy adult men underwent non-dominant forearm immobilization by plaster cast for 21 days. Five healthy adult subjects were designated as the immobilization (IMM) group and five were designated as the immobilization + training (IMM+TRN) group. Grip strength, forearm circumference, dynamic handgrip endurance and muscle oxygenation response were measured before and after the 21 day immobilization period. Using near-infrared spectroscopy (NIRS), muscle oxygen consumption recovery (VO₂mus) was recorded after a submaximal exercise and the recovery time constant (TcVO₂mus) was calculated. Reactive hyperemic oxygenation recovery was evaluated after 5 minutes ischemia. Two training programs were performed by the IMM+TRN group twice a week. One exercise involved a handgrip exercise at 30% maximum voluntary contraction (MVC) at a rate of 1 repetition per 1 second until exhaustion (about 60 seconds). The other involved a handgrip exercise at 70% MVC for 2 seconds with a 2 second rest interval, repeated 10 times (40 seconds).

Results

There was a significant group-by-time interaction between the IMM and IMM+TRN groups in the TcVO₂mus (p = 0.032, F = 6.711). A significant group-by-time interaction was observed between the IMM and IMM+TRN groups in the MVC (p = 0.001, F = 30.415) and in grip endurance (p = 0.014, F = 9.791). No significant group-by-time interaction was seen in forearm circumference and reactive hyperemic oxygenation response either in IMM or IMM+TRN group.

Conclusion

The training programs during immobilization period used in this experiment were effective in preventing a decline in muscle oxidative function, endurance and strength.