Learn how to tell good training discomfort from injury pain. A practical, evidence-based guide with a simple traffic-light system, return-to-training steps, and red-flag symptoms that mean stop and get assessed.

The Big Idea

Pain is information. It is not always a problem, and it is not always a green light. Training is learning to read the signal. The goal here is simple: help you know what pain to train through, what pain to modify, and what pain means stop and seek help.

You can use a traffic-light model:

- Green: normal training discomfort. Keep going.

- Yellow: caution. Modify load, range, tempo, or exercise and retest.

- Red: stop. Get assessed.

This article gives you the criteria for each, plus a step-by-step return-to-training plan.

Your Body’s Language: 3 Types of Pain

Green Light: Train

Sensation: muscle burn, tightness, symmetrical next-day soreness.
Timing: soreness peaks 24–72 hours after a new or harder session, then fades.
Quality: diffuse, not sharp; settles as you warm up.
Intensity: 0–3 out of 10.
This is typical DOMS and normal adaptation to training load.

Yellow Light: Modify

Sensation: dull, nagging ache, 3–5/10, limits certain movements.
Behavior: form tries to change to “protect.”
Pattern: keeps showing up on the same lift or position.
Often this is irritated tissue that prefers load management, not full rest. Tendon pain is a classic example, and it responds best to progressive loading with pain monitoring.

Red Light: Stop

Sensation: sharp or stabbing, “pop,” catching, instability, joint giving way.
Signs: swelling, heat, visible change, or neuro symptoms like numbness and tingling; pain 6–10/10 that escalates rep to rep.
Systemic: dark tea-colored urine with severe muscle pain or profound weakness after extreme exertion suggests rhabdomyolysis and requires urgent care.

DOMS vs. Injury Pain

DOMS is delayed soreness that arrives the next day, peaks around days 1–3, then settles within a week. It is usually symmetrical and linked to eccentric work or a new stimulus. It should not cause joint instability, locking, or neuro symptoms. Managing DOMS is about planned progression, sleep, light movement, and possibly soft-tissue work.

Injury pain often has one or more of these features: a sharp moment of onset, swelling, immediate loss of function, or pain that worsens during the set and does not “warm out.” If you cannot load the limb normally or your form collapses to compensate, treat it as yellow or red until proven otherwise.

Red Flags: When Pain Means Stop

Seek immediate medical care if you have any of the following:

Back or leg symptoms with cauda equina red flags: new urinary retention or incontinence, saddle numbness, rapidly worsening weakness.
Suspected fracture or dislocation: visible deformity, significant trauma, extreme point tenderness, inability to bear weight.
Infection, cancer, or serious illness signs: fever, night sweats, unexplained weight loss, history of cancer with new back pain.
Rhabdomyolysis red flags after extreme exertion or heat: severe muscle pain, profound weakness, dark tea-colored urine. Err on the side of the ER.

Acute Injury Care: What To Do First

For soft-tissue injuries, the most up-to-date guidance is PEACE & LOVE:

PEACE: Protect, Elevate, Avoid anti-inflammatories early, Compress, Educate.
LOVE: Load, Optimism, Vascularization, Exercise.

This framework emphasizes early education and a gradual return to loading rather than long rest.

Some authors propose variations for more severe swelling, but the core principle remains: protect in the short term, then progressively load according to symptoms.

Important: Early mega-doses of NSAIDs might blunt muscle adaptations in young adults during strength training. Use medication only as advised by your clinician.

The “Modify” Zone: Smart Tweaks That Keep You Training

If pain is in the 3–5/10 range and your form wants to change, modify rather than quit. Here are levers you can pull, one at a time:

Reduce load by 10–20 percent.
Shorten range slightly.
Slow tempo to 3-1-3 for control.
Swap implement or stance: barbell to dumbbells, bilateral to split.
Trim sets by 1–2 and retest.

For tendons, there is strong support for progressive loading like heavy slow resistance or controlled eccentrics. Some pain is acceptable if the 24-hour response returns to baseline by the next day.

Pain relief option for patellar tendinopathy: heavy isometrics can reduce pain for ~45 minutes and can be used before practice or training.

How to Return to Training After a Tweak

Think criteria-based, not calendar-based. Here is a clear, simple progression you can use for most non-serious musculoskeletal tweaks.

Step 1: Pain and Function Check

Pain at rest ≤2/10.
No giving way, locking, or neuro symptoms.
Daily tasks normal.
If any red-flag signs are present, stop and get assessed.

Step 2: Warm-Up and Retest

Do IRON Mobility Protocol for 5 minutes.

Retest the pattern with no load, then light load.
If symptoms ease as you warm up and stay ≤3/10, move to Step 3.

Step 3: Controlled Loading

Start at 60–70% of your normal training load for that lift, or choose RPE 6–7.
Keep reps clean and symmetrical.
Use the 24-hour rule: if pain and morning stiffness are the same or better the next day, progress. If worse, back off. This rule is standard in tendon rehab and carries well to other tissues.

Step 4: Progressive Return

Increase only one variable per session: load or volume or range.
Typical jumps are 5–10% load or 1–2 sets.
Keep pain ≤3/10 during and the next day.
For field moves or plyometrics, progress drills before chaos and ensure no 24-hour flare.

Step 5: Pass the Exit Tests

Full training session at normal loads with no symptom escalation in the 24 hours after.
Side-to-side strength within ~10 percent for unilateral work.
No compensations on your key lifts.
For lower limb sport moves, include hop or change-of-direction tests when relevant and pain-free.

Pattern Swaps and Exercise Alternatives

Pain often dislikes position more than it dislikes effort. Try these swaps inside the yellow zone:

Back squat bothers knee or back: Safety-bar squat to a box, or front-loaded goblet squat.
Flat bench pinches shoulder: neutral-grip dumbbell bench or slight incline; add a controlled pause.
Conventional deadlift stresses back: trap-bar deadlift, high-handle, or Romanian deadlift with shorter range.
Overhead press irritates shoulder: landmine press or half-kneeling single-arm press.

Use these only as long as needed. The goal is to work back toward your preferred pattern as symptoms settle.

Warm-Up That Actually Helps

A good warm-up raises temperature, rehearses positions, and gives you feedback before you load. Your IRON Mobility Protocol flow fits perfectly:

Initiate core and breath: 1–2 minutes of diaphragmatic breathing with a light brace.
Release tension: 1–2 minutes of targeted soft tissue or positional breathing.
Open key joints: controlled mobility for the day’s patterns.
Neural prep and prime: ramping sets and bar path rehearsal.

If pain lessens during the warm-up and remains ≤3/10, proceed with your plan. If it worsens, shift to the Modify Matrix.

Recovery That Works

What has strong support

Progressive exercise and education for low back pain. Walking programs reduce recurrence risk and extend pain-free time between flares.
Progressive loading for tendinopathy, including heavy slow resistance and careful pain monitoring.

What helps some people, modestly

Foam rolling or massage can reduce DOMS markers or stiffness, but effects on pain are modest and short-term. Use if it feels good, not because you “must.”

What to be cautious with

NSAIDs at high doses can blunt hypertrophic adaptations in young adults during resistance training. Use the lowest effective dose for the shortest time if your clinician recommends it.

General guideline highlights

For most non-specific low back pain, start with non-drug therapies, keep moving, and consider manual therapy only as part of a package that includes exercise and education. Imaging is rarely needed in the absence of red flags.

Three Quick Case Studies

Case 1: Quad DOMS After New Split Squats

Symptoms: diffuse quad soreness peaking day 2, eases with warm-up.
Plan: light cycling, IRON Mobility, easy full ROM bodyweight squats. Keep lower-body loads at 70% for 1–2 sessions, then progress.
Why: classic DOMS pattern. Exercise and time resolve it.

Case 2: Patellar Tendon Ache With Squats

Symptoms: 3–4/10 pain at patellar tendon during deeper knee angles, worse with fast eccentrics, better next day if load is lower.
Plan: shift to tempo split squats and leg press with heavy slow resistance, keep pain ≤3–4/10 during, and at or below baseline next morning. Use isometric leg extension holds for short-term analgesia before squats. Increase load or range every 2–3 sessions if the 24-hour response is stable.

Case 3: Sudden Sharp Low-Back Pain Pulling From the Floor

Symptoms: sharp, unilateral pain on pull, protective spasm, no neuro signs.
Plan: PEACE in the first 24–48 hours, gentle walking, then graded reloading with trap-bar pulls from blocks and braced hinge patterns. Consider a progressive walking and education plan to reduce recurrence risk long term. Seek urgent care if neuro red flags appear.

FAQ

Is soreness required to make gains?

No. Soreness is not a proxy for progress. You can grow and get stronger without heavy DOMS. Progressive overload and consistency matter most.

How much pain is “acceptable” when rehabbing a tendon?

Up to 3–4/10 during the session can be acceptable if your next-day symptoms are the same or better. If pain lingers or spikes, drop load or modify.

Do I need an MRI for back pain?

Usually not. Imaging does not correlate well with symptoms and is rarely needed without red flags. Stay active, follow a graded plan, and get assessed if symptoms persist.

Should I stretch a sore muscle?

Light mobility and gentle range can feel good, but aggressive stretching is not required to resolve DOMS. Focus on movement, progression, and sleep.

Are there training load rules to prevent injury?

Avoid sudden spikes in volume or intensity. There is mixed evidence on exact workload ratios, so use common sense progressions and the 24-hour response rule.

If you want help applying this to your training, I coach in person in Greenwich and remotely anywhere.

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References

Dubois B, Esculier J-F. Soft-tissue injuries simply need PEACE and LOVE. Br J Sports Med. 2020;54(2):72–73.
Beyer R, et al. Heavy Slow Resistance vs Eccentric Training in Achilles Tendinopathy. Am J Sports Med. 2015.
Morrison S, et al. Putting “Heavy” into Heavy Slow Resistance. Front Sports Act Living. 2022.
Malliaras P, et al. Patellar Tendinopathy: Load Progression and Return to Sport. JOSPT. 2015.
Rio E, et al. Isometric exercise induces analgesia in patellar tendinopathy. Br J Sports Med. 2015.
Cheung K, et al. Delayed-Onset Muscle Soreness. Sports Med. 2003.
Chen J, et al. DOMS characteristics and interventions: Systematic Review and Network Meta-analysis. 2025.
Qaseem A, et al. Noninvasive Treatments for Low Back Pain: ACP Guideline. Ann Intern Med. 2017.
Pocovi NC, et al. WalkBack Trial: Walking and Education Reduce Low-Back-Pain Recurrence. The Lancet. 2024.
Cashin AG, et al. Analgesic effects of non-surgical treatments for low back pain. BMJ EBM. 2025.
Lilja M, et al. High doses of NSAIDs compromise hypertrophy. Acta Physiol. 2018.
NICE NG59. Low Back Pain and Sciatica in over 16s. 2016–2020 updates.
CDC/NIOSH. Rhabdomyolysis: Signs and Symptoms. 2025.
Tietze DC, et al. Exertional Rhabdomyolysis in the Athlete: Clinical Review. 2014.

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