Hamstring Injuries: Symptoms, Causes, and Solutions

Hamstring injuries are among the most common injuries in sport. They mostly occur during sprinting with high levels of acceleration. Hamstring injuries tend to peak between ages 16–25, when sport performance and training volume also peak. The average athlete is sidelined for 21 days, and injuries commonly occur in-season. Symptoms can linger longer than that, and reinjury is incredibly common — as high as 31% in athletes.

Athletes in high-speed positions that demand maximal acceleration are most at risk, such as defensive backs and receivers in American football, midfielders in soccer, or competitive sprinters. Athletes at lower risk include offensive and defensive linemen, centers in basketball, and first and third basemen in baseball.

Hamstring Anatomy Breakdown

The hamstring is comprised of three major components:

• Semimembranosus (medial)

• Semitendinosus (lateral)

• Biceps femoris (central, long and short heads) — most commonly injured, usually in the tendinous region

Biomechanics of the Hamstring

The hamstring is responsible for hip extension (straightening) and knee flexion (bending).

The semimembranosus plays a role in hip internal rotation, while the semitendinosus plays a role in hip external rotation, although these are not their main functions.

I commonly refer to the hamstrings as the gas pedal of the lower extremity — they are the prime mover during acceleration in a sprint, which helps explain their susceptibility to overexertion during high-effort running.

A Quick Review of the Sprinting Gait Cycle

When we sprint, while one foot is in the contact phase with the ground, the contralateral foot (opposite side) is in swing phase. For brief moments as we switch between contact phases, we experience a flight phase, where no contact with the ground is being made.

Hamstring strains typically occur in the later phases of swing — when the leg is off the ground and decelerating knee extension (slowing down a straight knee).

Hamstring Strain Grading

• Grade 1: Mild pain or swelling, non-appreciable tissue disruption, no or minimal loss of function

• Grade 2: Identifiable partial disruption of tissue with moderate pain and swelling, leading to loss of function

• Grade 3: Complete disruption or tear of the musculotendinous unit with severe pain, swelling, and lack of function

When to Be Concerned

This content is strictly educational and not medical advice. You should always seek the opinion of a qualified healthcare provider who can evaluate you in person if you have concerns.

Some things worth looking out for include:

• Sudden pain in the back of the thigh (acute posterior thigh pain)

• A sudden pop, especially during a high-speed movement

• A stiff-legged gait, or avoiding bending the knee or hip

• Inability to bear weight

• Bruising, redness, or pain to the touch on the back of the thigh

• Pain greater than 4/10 on a standard pain scale

How to Get Back to Training and Doing What You Love

Step 1: Confirm the Injury

With any injury, the first step is confirming what it is, how severe it is, and what stage of healing you're in.

There are a few different injuries that can present similarly to a hamstring strain, so it's important these are ruled out before continuing. You do this with a licensed professional who works with sports and orthopedic injuries — I can't emphasize this enough.

Don't rely on your friend at the gym, a guy you've never met on Instagram, or an AI trained to give you generic information for a diagnosis. Go to your physical therapist, athletic trainer, primary care provider, or orthopedist.

Step 2: Define Your End Point

Once you've been diagnosed and know where you are, the next step is figuring out where you want to be.

What are you returning to — sport, training, being able to keep up with your kids? Whatever the goal is, you need to know it so you can Start With The End In Mind.

This also allows us to apply one of my favorite principles in strength and conditioning: specificity. Simply put, whatever you're training or rehabbing is what you'll adapt and improve. If I'm training strength, I'll get stronger — but that doesn't necessarily mean my endurance improves just because I'm training or rehabbing in general.

Step 3: Find Your Entry Point

This varies for everyone. For example, the entry point for a 55-year-old father of three who strained his hamstring playing catch with his sons will be different than a female competitive black belt who strained hers playing guard during her sixth training session of the week.

• The mechanism of injury (how they got hurt) is different for both

• The type and severity of injury may be different

• They are different people altogether

• They most likely have different end points they hope to return to

Step 4: Progress Slowly

This is probably the most underrated piece of advice you'll read, but push the envelope in your rehab while staying reasonable with the timeline. Go Fast to Go Short. Go Slow to Go Far.

Yes, I want you to work hard, and I want you to get back to your sport as soon as possible. But hamstring strains commonly get re-strained, sending athletes into a cycle of reinjury over and over again. Address it completely the first time, and it'll save you a headache down the line.

Average time of play lost is about 3–6 weeks depending on injury severity, but recurring hamstring injuries can extend that to 3–6 months (Poudel B, et al).

If you give it the proper time and rehab well, you'll likely come back at 100%. If you rush it, you risk ending up back at square one.

Step 5: Test It

Return-to-sport testing is incredibly important for all injuries. Some injuries are well studied for what we should test before clearance; others are based on the specific demands of the sport and the expertise of the provider you're working with.

At Delta Performance and Rehab, we have our own return-to-sport testing protocols for most sport injuries. Our plans of care typically begin and end with testing — establishing a baseline, then confirming you've hit the benchmark before clearing you. If your rehab program doesn't include some form of this, you're most likely not working with a true sports rehab professional.

Step 6: Return to Participation — With a Plan

When you do go back to your sport, have a plan. It should look something like this:

Return to Participation (50% of previous level) → Return to Performance (75% of previous level) → Full Return (100% of previous level)

Your physical therapist or orthopedist should be able to help you structure this. If they say "go back and just take it slow" without anything more specific, that's a red flag — especially if you're within that first 3-week window. Find a provider with a clearer answer.

Closing Thoughts

Hamstring injuries are common, but common doesn't mean simple. The high reinjury rate isn't bad luck — it's usually the result of returning to sport based on a calendar instead of a clear, tested plan. The athletes who come back strongest are the ones who get an accurate diagnosis early, train with a clear end point in mind, and don't skip the testing phase before returning to full competition.

If you're dealing with a hamstring injury — whether it just happened or it's one that keeps coming back — don't guess your way through it. At Delta Performance and Rehab, we build your rehab around real return-to-sport testing, not just a timeline on a calendar. Our Doctors of Physical Therapy use objective data to confirm you're actually ready before you step back on the field, not just hope you are.

Ready to get back to your sport the right way? Book a free discovery call and let's build your return-to-sport plan.

Reference: Poudel B, et al.