A non-volitional skeletal muscle endurance test measures functional changes associated with impaired blood flow.

Introduction: An electrically stimulated intermittent fatigue test using mechanomyography was recently proposed as a possible tool for detecting clinically relevant changes in muscle function. This study was designed to determine whether the proposed test can detect additional fatigue when it should be present. Methods: Subjects (n = 10) underwent two trials each (occluded and normal blood flow) with a standardized fatigue protocol on the Ankle Dorsiflexors (AD) and Wrist Extensors (WE) using a clinical electrical stimulator. Results: Mean normalized twitch acceleration was strongly predictive of mean normalized torque (R 2 = 0.828). The WE experienced lower twitch magnitudes throughout the tourniquet trial (10.81 ± 1.25 m/s2) compared to normal blood flow (18.05 ± 1.06 m/s2). The AD twitches were overall reduced in the tourniquet trial (3.87 ± 0.48 m/s2) compared with the control trial (8.57 ± 0.91 m/s2). Conclusion: Occluding blood flow to a muscle should cause greater muscle fatigue. The ability to detect reduced contraction magnitudes during an electrically stimulated fatigue protocol resulting from low blood flow suggests the proposed test may be capable of detecting clinically relevant muscle deficits.

Downhill Running Impairs Activation and Strength of the Elbow Flexors.

ABSTRACT: Brandenberger, KJ, Warren, GL, Ingalls, CP, Otis, JS, and Doyle, JA. Downhill running impairs activation and strength of the elbow flexors. J Strength Cond Res 35(8): 2145-2150, 2021-The purpose of this study was to determine if knee extensor injury induced by 1 hour of downhill running attenuated force production in the elbow flexors. Subjects completed either downhill running for 1 hour (injured group; n = 6) or sedentary behavior (control group; n = 6). Strength and voluntary activation (%VA) were measured by isometric twitch interpolation of the elbow flexor and knee extensor muscles at the following time points in relation to the injury: before injury (Pre), after injury (Post), 24 hours after injury (24Post), and 48 hours after injury (48Post). Mean (±SE) knee extensor strength was significantly reduced (53.5 ± 9.9%) Post and remained reduced at 24Post and 48Post in the injury group. Knee extensor muscle twitch strength was reduced Post and 24Post after the downhill run (p < 0.022). Elbow flexor muscle strength was significantly reduced Post (13.2 ± 3.9%) and 24Post (17.3 ± 4.0%). Elbow flexor muscle twitch strength was not significantly different at any time point. Elbow flexor muscle %VA was not significantly reduced compared with Pre, at Post (16.2 ± 5.1%), 24Post (20.9 ± 6.7%), or 48Post (12.9 ± 4.5%). A 1-hour downhill run significantly injured the knee extensors. The elbow flexor muscles remained uninjured, but strength of these muscles was impaired by reduced %VA. These data suggest muscle injury can lead to prolonged strength deficits in muscles distant from the injury and should be accounted for when scheduling training that may lead to delayed-onset muscle soreness.

A retrospective analysis of associations between BMI and days spent on mechanical ventilation in a level 1 trauma facility.

OBJECTIVE: To examine whether BMI impacts the outcomes of mechanically ventilated patients. METHODS: Data was collected retrospectively among patients involved in motor vehicle accidents in intensive care at a major trauma center in Atlanta, GA. Patients were categorized into five BMI groups: underweight (BMI < 18.5), normal weight (BMI of 18.5-24.9), overweight (BMI of 25-29.9), obese (BMI of 30-39.9), and morbidly obese (BMI of >40). RESULTS: Among all patients (n=2,802), 3% of patients were underweight, 34% were of normal weight, 30% were overweight, 27% were obese, and 6% were morbidly obese. The mean number of ventilator days for normal weight patients was 4.6, whereas the mean number of ventilator days for underweight and morbidly obese patients were higher (10.3 and 7.4, respectively). CONCLUSIONS: Underweight and morbidly obese populations may require additional interventions during their ICU stays to address the challenges presented by having an unhealthy BMI.

Consumption of a 5-mg Melatonin Supplement Does Not Affect 32.2-km Cycling Time Trial Performance.

Brandenberger, KJ, Ingalls, CP, Rupp, JC, and Doyle, JA. Consumption of a 5-mg melatonin supplement does not affect 32.2-km cycling time trial performance. J Strength Cond Res 32(10): 2872-2877, 2018-Some studies suggest that exogenous melatonin supplementation may improve athletic performance in hot humid environments because of its precooling effect. However, melatonin is also consumed as a sleep aid for its depressive effects on the central nervous system (CNS), which may hinder performance. Therefore, this study was conducted to determine whether consuming a 5-mg supplement of melatonin would affect performance in a laboratory-simulated 32.2-km cycling time trial. The time trial was conducted in a thermoneutral environment to separate CNS depressive effects of the melatonin from the cooling effects. Trained male subjects (n = 10; V[Combining Dot Above]O2max = 62.7 ± 6.3 ml·kg·min; age = 25.1 ± 4.0 years; mass = 69.9 ± 9.1 kg; height = 176.0 ± 7.1 cm) performed three 32.2-km time trials on an electronically braked cycle ergometer. The first trial was a familiarization. During the 2 experimental trials, subjects received in a random order either a placebo or a 5-mg melatonin supplement 15 minutes before exercise in a double-blind, crossover design. Variables were measured before exercise and at 8-km intervals. The mean 32.2-km time trial completion times for the melatonin (64.94 ± 5.95 minutes) and placebo (65.26 ± 6.85 minutes) trials were not different (p = 0.682). The mean time trial power output for the melatonin (190.4 ± 40.4 watts) and placebo (190.0 ± 45.7 watts) trials was not different (p = 0.927). Rectal temperature was not significantly different for melatonin compared with placebo (p = 0.827). These results suggest that a 5-mg melatonin supplement administered 15 minutes before exercise does not measurably impact the performance of a 32.2-km cycling time trial in a thermoneutral environment.