BLUF (Bottom Line Up Front)
Military operational training—designed to mimic combat and survival stress—leads to significant short-term declines in physical performance. This meta-analysis of 17 studies (N = 1,592) found consistent reductions in lower body power and muscular endurance following training. These performance drops are attributed to combined stressors like sleep deprivation, caloric deficit, and extended physical exertion. While temporary, these declines can hinder real-world mission effectiveness and raise injury risks if not properly managed with recovery protocols.
Purpose of the Study
The authors set out to evaluate how real-world operational training environments—those simulating combat, survival, and sustained military tasks—impact physical performance in active-duty personnel. These stress-heavy environments involve:
- High physical demands (rucking, obstacle courses, combat simulations)
- Sleep deprivation
- Caloric deficits
- Harsh environments (mountain, jungle, arctic)
The goal was to identify which physical fitness attributes degrade most during and after operational training to guide future preparation and recovery practices.
Study Details
Study Type: Meta-analysis
Total Studies Included: 17
Total Participants: 1,592
Population: Active-duty military personnel only
Training Durations: Ranged from 1 to 62 days
Training Types Included:
- U.S. Army Ranger School
- Navy SERE (Survival, Evasion, Resistance, Escape) Training
- Marine Raider Individual Training Course
- Special Forces Training
- Environmental Survival Training
- Arctic and Field Training Exercises
- Night Operations
Performance Metrics Assessed
Nine physical performance constructs were analyzed:
| Construct | Subcomponents |
|---|---|
| Lower Body Power | Jump Distance, Jump Power |
| Muscular Endurance | Upper Body (e.g. push-ups), Core (e.g. sit-ups) |
| Upper/Lower/Full Body Strength | Handgrip, Bench Press, Leg Press, etc. |
| Aerobic Endurance | 2–4 km run, VO₂max, loaded march |
| Anaerobic Capacity | 300-yard run, sprints |
| Agility | Shuttle runs |
| Upper Body Power | Bench throws, medicine ball throws |
Key Results
↓ = Decline observed
| Fitness Trait | Effect Size (Hedge’s g) | Magnitude | Evidence Strength | Change (%) |
|---|---|---|---|---|
| Lower Body Jump Power | g = 0.87 | Large ↓ | Limited | ~11% ↓ |
| Lower Body Jump Distance | g = 0.39 | Small ↓ | Strong (short duration) | ~6.5% ↓ |
| Upper Body Muscular Endurance | g = 0.40 | Small ↓ | Moderate | ~5% ↓ |
| Core Muscular Endurance | g = 0.46 | Small ↓ | Moderate | ~6.5% ↓ |
| Aerobic Endurance | g = 0.66 | No sig. change | Moderate | Mixed results |
| Upper/Lower/Full Body Strength | N/A | No change | Moderate | — |
| Anaerobic Capacity/Power | N/A | No change | Moderate | — |
| Agility | g = -0.14 | No change | Moderate | — |
| Upper Body Power | g = 0.11 | No change | Moderate | — |
Why the Declines Happen
Operational training mimics combat stress with little rest. Several physiological mechanisms contribute to performance loss:
- Type II muscle fiber fatigue → Reduced jumping and power output
- Sleep deprivation → Impairs reaction time, muscular strength, and endurance
- Caloric deficit → Leads to catabolic state, muscle atrophy, and reduced strength
- Neuromuscular fatigue → Disrupts motor control and voluntary muscular effort
- Hormonal shifts → Increased cortisol, decreased testosterone and GH impair recovery
Performance Areas Resistant to Decline
Surprisingly, some traits were stable or even improved:
- Aerobic and Anaerobic Capacity: No consistent drop, likely due to cardiovascular adaptations
- Upper and Lower Body Strength: Maintained, possibly due to muscular endurance gains or insufficient stress duration to cause loss
However, researchers note these results may be influenced by small sample sizes or inconsistent assessment methods.
Operational Implications
- Lower Body Power and Muscular Endurance are most at risk.
- These attributes are essential for sprinting, lifting, jumping, and movement under load—all common in combat scenarios.
- Temporary performance loss may limit tactical effectiveness and increase injury risk.
Conclusion
Operational training is effective at preparing soldiers for real-world stress, but not without trade-offs. Lower body power and muscular endurance decline most following multi-day, high-stress operations. While these declines are likely reversible with recovery, leaders should be aware of short-term performance losses and plan accordingly for both mission readiness and injury prevention.
Bibliography
Murray, A., Fraser, J.J., Bazett-Jones, D.M., & Norte, G.E. (2025). Changes in Physical Performance Following Operational Military Training: A Meta-Analysis. Sports Medicine – Open, 11(16). https://doi.org/10.1186/s40798-025-00815-y