Related Experiment Video
Updated: Jul 12, 2026
06:00
Modeling Highly Repetitive Low-level Blast Exposure in Mice
Published on: May 24, 2024
Physiological consequences of U.S. Army Ranger training.
Bradley C Nindl1, Brian R Barnes, Joseph A Alemany
1Military Performance, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. Bradley.Nindl@NA.AMEDD.Army.Mil
Medicine and Science in Sports and Exercise
|September 1, 2007
Summary
Intensive U.S. Army Ranger training significantly reduced soldiers' physical performance, including strength and power, and altered body composition and hormones. Lower-body power is a key indicator of these physiological changes.
Area of Science:
- Exercise Physiology
- Military Science
- Endocrinology
Background:
- Soldiers require high physical readiness for operational effectiveness.
- Intensive military training can lead to significant physiological stress and performance degradation.
Purpose of the Study:
- To investigate the physiological effects of U.S. Army Ranger training.
- To assess changes in strength, power, body composition, and somatotrophic hormones.
Main Methods:
- 50 male soldiers underwent an 8-week training course with a daily energy deficit.
- Measurements included lower-body power, maximal strength, body composition, and serum hormone levels before and after training.
Main Results:
- Significant declines observed in power output, maximal strength, body mass, fat-free mass, and fat mass.
- Total testosterone and IGF-I decreased, while cortisol increased.
- Lower-body power correlated with fat-free mass changes; IGF-I and cortisol correlated with tissue mass loss.
Conclusions:
- Lower-body power, assessed via vertical jump and body mass, is a practical measure of training impact.
- Severe weight loss (>13%) shows closer correlation of IGF-I and cortisol with soft tissue changes than testosterone.
Related Concept Videos
01:38Cognitive Dissonance
Social psychologists have documented that feeling good about ourselves and maintaining positive self-esteem is a powerful motivator of human behavior (Tavris & Aronson, 2008). In the United States, members of the predominant culture typically think very highly of themselves and view themselves as good people who are above average on many desirable traits (Ehrlinger, Gilovich, & Ross, 2005). Often, our behavior, attitudes, and beliefs are affected when we experience a threat to our...
01:20Exercise and Cardiovascular Response
Exercise significantly impacts cardiovascular response, which is crucial for understanding patient health and designing effective treatment plans.
Light to moderate physical activity initiates a series of interconnected responses in the body. The heart rate modestly increases in anticipation of the workout, followed by widespread vasodilation as oxygen consumption by skeletal muscles increases. This results in decreased peripheral resistance, increased capillary blood flow, and accelerated...
Light to moderate physical activity initiates a series of interconnected responses in the body. The heart rate modestly increases in anticipation of the workout, followed by widespread vasodilation as oxygen consumption by skeletal muscles increases. This results in decreased peripheral resistance, increased capillary blood flow, and accelerated...
01:16Sympathetic Activation
The sympathetic division can influence tissues and organs by releasing norepinephrine at peripheral synapses and distributing epinephrine and norepinephrine through the bloodstream. In times of crisis or stress, sympathetic activation occurs, which is regulated by sympathetic centers in the hypothalamus. As a result, sympathetic activation prepares the body for physical exertion, rapid ATP production, and heightened alertness, allowing individuals to respond effectively to challenging or...
01:27Exercise and Muscle Performance
Exercise induces a range of adaptations in muscle tissue, depending on the type and duration of activity. Such physical training can be broadly categorized into two types: endurance exercises and resistance exercises.
Endurance exercises
Endurance exercises involve running, swimming, or cycling, which require repetitive movements with low force output. When a person engages in endurance exercise, a few noticeable changes occur in their skeletal muscles. For instance, the number of capillaries...
Endurance exercises
Endurance exercises involve running, swimming, or cycling, which require repetitive movements with low force output. When a person engages in endurance exercise, a few noticeable changes occur in their skeletal muscles. For instance, the number of capillaries...
04:49Robbers Cave
During the 1950s, the landmark Robbers Cave experiment demonstrated that when groups must compete with one another, intergroup conflict, hostility, and even violence may result. At the Oklahoman summer camp, two troops of boys—termed the Rattlers and the Eagles—took part in a week-long tournament. During this time, their negativity culminated in derogatory name-calling, fistfights, and even vandalism and destruction of property. However, this work also revealed that such tension could be...
01:25Physiological Barriers
Physiological barriers are semi-permeable cellular structures restricting drug diffusion into intracellular compartments and tissues. There are six types of physiological barriers: blood endothelial, cell membrane, blood-brain, blood-cerebrospinal fluid (CSF), blood-placenta, and blood-testis barriers.
The blood endothelial barrier is the most porous of these. It allows all small ionized, un-ionized, and lipophilic molecules to pass through the endothelial lining into the interstitial space...
The blood endothelial barrier is the most porous of these. It allows all small ionized, un-ionized, and lipophilic molecules to pass through the endothelial lining into the interstitial space...