Researchers studied 200 military recruits to understand why some get stress fractures (tiny cracks in bones) during intense training. They found that recruits with weaker bones were much more likely to get injured, and those who were underweight or overweight had even weaker bones. Interestingly, vegetarian recruits had more bone problems than meat-eaters. The study suggests that military training programs should check recruits’ bone strength and make sure they’re eating enough of the right nutrients to keep their bones healthy during tough physical training.

The Quick Take

  • What they studied: Whether military recruits with weaker bones get more stress fractures during training, and how weight and diet affect bone strength
  • Who participated: 200 active military recruits in India, average age 26 years old, including both regular soldiers and officers
  • Key finding: Recruits with weak bones were nearly 8 times more likely to get stress fractures. About 1 in 4 recruits had weak bones, and 1 in 6 got stress fractures during training
  • What it means for you: If you’re doing intense physical training, getting your bones checked and eating well (especially calcium and protein) might help prevent painful injuries. This is especially important if you’re underweight or overweight

The Research Details

Scientists measured the bone strength of 200 military recruits using a special ultrasound machine that scans the heel bone. They also calculated each person’s weight-to-height ratio (BMI) and asked them about their diet, job rank, and lifestyle habits. They then looked at medical records to see who had gotten stress fractures during training.

This type of study is like taking a snapshot in time—researchers looked at everyone once and compared the people who had injuries to those who didn’t. They used math to figure out if weak bones, weight problems, or diet differences were connected to stress fractures.

The researchers measured bone strength using a heel bone scan because it’s quick, safe, and gives a good picture of overall bone health. They confirmed stress fractures by checking medical records and X-rays when available.

This study design is practical because it shows what’s actually happening in real military training situations, not in a lab. By looking at many recruits at once, scientists can spot patterns—like whether certain groups (officers vs. regular soldiers, vegetarians vs. meat-eaters) have more bone problems. This helps military leaders know who might need extra support.

The study included a decent-sized group (200 people) and used actual medical records and X-rays to confirm injuries, which makes the findings more trustworthy. However, because it’s a snapshot study, we can’t be 100% sure that weak bones cause fractures—only that they’re connected. The study was done in India, so results might be slightly different in other countries with different diets and training styles.

What the Results Show

The researchers found that about 1 in 4 recruits (24.5%) had weak bones, even though they were doing intense physical training. This was surprising because you’d expect military training to make bones stronger. About 1 in 6 recruits (16%) had gotten stress fractures.

The biggest finding: recruits with weak bones were much more likely to have stress fractures. Of the recruits who got stress fractures, 78% had weak bones. This is a very strong connection—it suggests that bone strength is one of the most important things protecting against these injuries.

Recruit weight also mattered. Those who were underweight or overweight were more likely to have weak bones. Officers (assistant commandants) had weaker bones than regular soldiers, which might be because they do different types of training or have different diets.

Diet made a big difference too. Vegetarian recruits had significantly more weak bones and stress fractures than those who ate meat. This suggests they might not be getting enough protein or certain nutrients their bones need.

The study found that job rank was connected to bone strength—officers had weaker bones than regular soldiers. This could mean different training loads, different nutrition, or different stress levels between ranks. The connection between vegetarian diet and weak bones was particularly strong, suggesting that vegetarian recruits might need special attention to eating enough protein and other bone-building nutrients.

Other studies have shown that intense physical training usually makes bones stronger, so finding weak bones in military recruits was unexpected. However, previous research has shown that not eating enough calories or protein can weaken bones even during exercise. This study supports the idea that nutrition is just as important as exercise for bone health. The finding about vegetarian diets matches some previous research suggesting that plant-based diets need careful planning to get enough bone-building nutrients.

This study only looked at one group of Indian military recruits at one point in time, so we can’t be sure the results apply to other countries or other types of athletes. The study shows that weak bones and stress fractures are connected, but we can’t prove that weak bones actually cause the fractures—only that they go together. The researchers didn’t measure exactly how much calcium, protein, or other nutrients each person ate, so we can’t be completely sure diet is the reason for the differences. Some recruits might have had weak bones before they joined the military, which the study couldn’t determine.

The Bottom Line

Military training programs should: (1) Screen recruits’ bone strength before or early in training—this is moderately important based on this evidence; (2) Make sure recruits eat enough protein and calcium, especially vegetarian soldiers—this is important; (3) Help underweight or overweight recruits get to a healthy weight—this is moderately important; (4) Consider extra nutrition support for officers and those with weak bones—this is important. These recommendations have moderate to strong evidence from this study.

Military leaders and training programs should definitely pay attention to this research. Athletes doing intense training, especially those who are vegetarian, underweight, or overweight, should consider getting their bone strength checked. Anyone starting a new intense exercise program might benefit from making sure they eat enough calcium and protein. People who are already injured or have a family history of weak bones should definitely talk to a doctor.

Bone strength changes slowly—it usually takes several months of good nutrition and exercise to see improvements. Stress fractures can develop over weeks to months of repetitive training. If someone starts eating better and gets to a healthy weight, they might see bone strength improvements in 3-6 months, but it could take longer.

Want to Apply This Research?

  • Track daily calcium and protein intake (target: 1000-1200mg calcium, 50-60g protein daily) and weekly weight changes. Set a goal to reach a healthy BMI range and monitor it monthly.
  • Users should log meals to ensure adequate calcium (dairy, leafy greens, fortified foods) and protein (meat, eggs, legumes, nuts) intake daily. Set reminders for calcium-rich snacks and track weight trends to stay in a healthy range.
  • Monthly BMI tracking, quarterly nutrition reviews focusing on calcium and protein, and annual bone health check-ups if doing intense training. Users should note any new aches or pains that might indicate stress fractures and report them to a healthcare provider.

This research describes patterns in one group of military recruits and should not be used for self-diagnosis. If you have bone pain, suspect a stress fracture, or are concerned about your bone health, please consult with a doctor or healthcare provider. This study is observational and cannot prove that weak bones cause stress fractures, only that they are associated. Individual results vary based on genetics, training intensity, overall health, and many other factors. Always talk to a healthcare professional before making major changes to your diet or exercise routine, especially if you have existing health conditions.