Personal trainers cost money, judge you silently, and occasionally make you do burpees. AI trainers are free, polite, and available at 11pm. So I asked the obvious question: can ChatGPT, Gemini and Claude actually watch me exercise and tell me what I'm doing wrong? Or will they just recite "engage your core" at whatever video I upload, including one of my cat?
The Experiment
I filmed the below two 45-second high planks (straight arms) from the side, in the same room. In one, my hips are lower. In the other, they're noticeably higher, a slight pike. The difference is obvious to the naked eye. For this test, the lower one is the correct plank and the higher one is the mistake.
Plank L (Video 1)
Plank H (Video 2)
Each model got each video three times, every time in a fresh chat. That's 18 runs in total, with the same prompt every time:
"Act as my personal trainer. Monitor my plank and give me objective feedback."
Two videos test whether a model is actually looking. Three runs test whether for the same video its verdict is consistent. Generic plank advice sounds expert on any video; it just can't tell two different videos apart.
The Results
A ✅ means every run met the criterion
The Analysis
TL;DR: Claude was the only trainer that reliably told my two planks apart. ChatGPT built the best system for tracking progress. Gemini couldn't agree with itself, or with the footage.
Only Claude spotted the difference reliably. It called my correct plank level in all three runs and flagged the one with hips up as "too high" in all three. ChatGPT called both planks basically fine, except for one run that caught the pike.
Gemini was all over the place with its diagnosis. It told me my correct plank was too high (twice) and that it was sagging (once), complete with a "pronounced arch" and instructions to raise my hips "a couple of inches." On the high hips plank, two runs praised my "level" hips, and the third flagged the pike and an arched lower back, which are opposite faults.
ChatGPT aced tracking and report generation. It created a framework to score objectively, and assigned me a score. In the real world this is the kind of feedback that motivates action.
All three identified plank type and estimated the hold time within a few seconds.
The neck dispute. Claude said my head drooped in all six runs and ChatGPT agreed in four. Gemini called my neck "neutral" five times. With no trainer in the room, that one stays unresolved.
The answer to why the 3 models perform so differently on a task mostly lies in how each model ‘watches’ a video. They do it in fundamentally different ways.
Gemini 3.1 Pro takes video natively. Google's documentation samples about one frame per second and recommends roughly 70 tokens per frame for general video, reserving a 280-token setting for "small details within video frames."
GPT-6 can't take video at all: OpenAI's model page lists video input as "not supported." So ChatGPT has to turn my clip into stills first, and its answers kept citing "the sampled frames."
Claude Opus 5.5 can't take video either (its documentation lists image formats only), so it took the video apart. Its activity logs show the same routine in every run: inspect the file, pull frames (every 4 seconds in most runs), tile them into a contact sheet, then crop close-ups of my body at several points in the hold and stack them for comparison.
A plank is essentially still life. To be able to do this task well is to correctly catch the angle of one line a few centimetres at the hip.
Before we go into a proper explanation of the mechanics of what most likely happened here, think through this example. What do you do when the text in a photo is too small to read on your phone? You don't just stare harder and longer at the full picture! You pinch to zoom on the part you care about. That's very similar to what is happening here.
To better understand this technically you need to know what a token is in this context. When a model looks at an image, it doesn't see pixels. It breaks the picture into small patches, and each patch becomes one token.
Each model gets a fixed number of tokens per picture, so more tokens on something means more detail on it. Claude's documentation puts it at 28×28 pixels per token. Claude cropped the room out first, so my body filled each image, then looked with up to 4,784 tokens per image. My hips went from one token to dozens, and a few centimetres became visible.
Gemini spread about 70 tokens across each whole frame: ceiling, TV, walls, floor, and me. I'm a thin strip at the bottom of the shot, so I got only a handful of them, and my hips, the one thing being judged, landed inside roughly one token. A few centimetres higher or lower, that token looks about the same. A plank also doesn't move, so fifty frames don't help. They're fifty copies of the same blurry view.
ChatGPT diagnosed the same issue ("the camera is relatively far away") but never zoomed in.
But why was Gemini random?
I can't confirm what settings the Gemini app uses, so this is an educated guess. When the visual evidence is too thin to decide, a model fills the gap with what plank feedback usually says. "Hips too high" and "hips sagging" are the two most common plank corrections on the internet, so each fresh chat effectively drew one. That would explain both the swinging and why its verdicts didn't track the footage.
The irony is that native video is Gemini's headline strength. And it's genuinely better at things that move. Google demos it on golf swings at 10 frames per second. For a pose that doesn't move, though, choosing where to look beats watching everything. Google seems to agree: in September it launched "agentic video understanding," which lets Gemini decide which parts of a video to inspect, though for now only on its Flash models and only for developers.
The company strategies are visible too in each model's response. Google built Gemini's video understanding for scale and events, which suits YouTube better than a single pose. ChatGPT is a consumer product, and it showed: widgets, scorecards, quick-reply buttons and ads, which is exactly why it won on tracking. Anthropic has bet heavily on agents that use tools, and Claude behaved like an analyst with a toolbox: handed a video it couldn't watch, it cut out, cropped and compared exactly the frames it needed.
The Moat
Here's what 18 runs taught me that one chat never would: every answer is a draw from a lottery. In real life you'd upload once, get one answer, and never see the other two. You'd never know whether you got Gemini's "lower your hips" or Gemini's "raise your hips."
A human trainer's call has their name on it. They'd settle the neck question in two seconds by looking. They'd also have their reputation at stake if they give you advice and it goes wrong. So they'll care more. That's accountability, and it's your human moat.
In practice, when using AI for physical task validation my advice would be:
Ask ChatGPT for a tracking framework. Then have a human validate it (ideally an expert but once you have the framework even a non expert works)
Trust AI when the answer is in a timestamp. Ask AI for the timestamp where it found the answer. Then head to it and validate.
Use Claude when footage is wide and success relies on catching a detail in a small portion of it.
If using Gemini for something that's not very dynamic, film it such that what you care about is front and center with not a lot of other distractions in the image.
For anything with long term impact (such as form in an exercise) invest in getting an expert opinion once. Record that opinion as a reference.
—-----------------------
The Transcript
Prompt (identical in all 18 runs): "Act as my personal trainer. Monitor my plank and give me objective feedback."
Video 1, hips lower (the correct plank): a 53-second clip
Video 2, hips higher (the pike): a 47-second clip
Every run was a fresh chat. The responses below are verbatim. Gemini's inline "MOV" citation chips are left out, ChatGPT's stock-photo illustrations are marked [image], its ad cards are marked [Ad], and the answer option ChatGPT had highlighted in each quick-reply box is shown as (•).
Claude (Opus 5.5)
Claude · Video 1 (hips lower) · Run 1
Tool activity: "Read 2 files, ran 3 commands"
I watched your whole clip from start to finish. You held a high plank (on straight arms) for about 45–48 seconds before your knees came down, and your form held up well for most of it.
What you're doing well
Hands are in the right place. Your wrists sit about under your shoulders and your arms stay straight the whole time. That gives you a stable base.
Your hips stay level. From the side, your shoulders, hips and ankles stay in a fairly straight line from the first second to the last. Your hips don't sag much and you don't push your bottom up into a tent. This is the hardest part of a plank, and you've got it.
You hold steady. There's no visible shaking or shifting. You lowered to your knees under control instead of collapsing.
What to fix
Your head drops, and it gets worse over time. In the first few seconds your head is roughly level with your spine. By about 15 seconds it's hanging down, with your hair falling toward the floor, and it stays that way to the end. This is the clearest issue in the video. A hanging head strains your neck and usually means your upper body is starting to switch off. Fix: tuck your chin slightly and look at the floor a little in front of your hands. Your ears should line up with your shoulders.
Your shoulders look a bit passive. Your upper back seems to sink a little between your shoulder blades in the later frames. Fix: push the floor away so your upper back fills out slightly, and keep that push going the whole time.
Squeeze your glutes and thighs. Your line is already good. Tensing your bum and thighs will help you keep it as you build toward longer holds.
How sure I am: the side-on camera angle is ideal for this. Your loose shirt hides the exact line of your lower back, though, so I can't rule out a slight dip there. A fitted top would let me check it properly next time.
Next step: fix your head position first. A 45-second hold with a neutral neck is worth more than a 60-second hold with your head hanging. Try 3 rounds of 30–40 seconds with perfect form. Once your head stays up the whole time, add 5–10 seconds per week.
How did it feel? Did it get hard in your shoulders, your core, or somewhere else? That tells me which of these to focus on first.
Claude · Video 1 (hips lower) · Run 2
Tool activity: "Read 7 files, ran 5 commands"
Nice work. You held a high plank (on your hands) for about 46 seconds, from roughly 0:01 to 0:47, and your body line stayed steady the whole time. I checked frames from start to finish. Here's what I saw.
What you're doing well
Hips: From shoulders to heels you're close to a straight line. Your hips don't sag toward the floor, and they don't pike up much. This is the hardest part of a plank to get right, and you held it the whole way through.
Arms: Your hands sit roughly under your shoulders and your elbows are straight without locking hard. That's a good base for your wrists and shoulders.
Consistency: Your position at 40 seconds looks almost the same as at 8 seconds. Your form held up as you got tired, which is a good sign the duration suits you right now.
Exit: You came down to your knees under control instead of dropping.
What to fix
Your head drops, and it gets worse over time. This is the clearest issue. In the first few seconds your neck is close to neutral. By about 16 seconds your head is hanging below your shoulders with your chin tucked toward your chest, and it stays there. Fix: look at a spot on the rug about 30 cm in front of your hands, and keep the back of your head in line with your spine.
Your upper back may be sinking between your shoulder blades. I can't confirm this from a side view, so treat it as a maybe. Some frames suggest your chest is sinking between your shoulders. Try pushing the floor away a little, so the area between your shoulder blades rises slightly.
Squeeze your glutes and brace like you're about to be poked in the stomach. I can't see muscle engagement on video. But actively squeezing makes the same 46 seconds work much harder, and it protects your lower back if your form starts to slip.
Limits of this review: I looked at frames every few seconds from one low side angle, not every moment. Small shifts in between, or anything hard to see from the side (like hip rotation or hand position), could have slipped past me.
Next step: Before adding time, do 3 rounds of about 40 seconds with your neck neutral the whole way, resting 30 to 45 seconds between rounds. Once that feels solid, add 5 to 10 seconds per round.
Two questions so I can coach you better: what's your goal with planks (core strength, posture, a specific time)? And did anything feel uncomfortable, like your wrists, shoulders or lower back? If you film the next one with the camera at hip height, I can give you a more precise read on your hips and back.
Claude · Video 1 (hips lower) · Run 3
Tool activity: "Read 4 files, searched the web, ran 7 commands"
I watched all 53 seconds and checked frames from the start, middle and end of the hold. One limitation first: I couldn't run automatic pose-tracking here, so this is a frame-by-frame visual read, not measured joint angles.
Overall: a good, honest plank 👍 You held a high plank from about 1s to about 48s, so roughly 47 seconds without stopping, and you came down in control onto your knees instead of collapsing. That's solid work.
What you're doing well
Arms and hands: Your arms stay straight and your hands sit roughly under your shoulders the whole time. That's where they should be.
Body line: From shoulders to ankles you're mostly straight. There's no obvious pike (hips up high) and no big sag. From this camera angle I can't confidently call a small hip dip either way.
Steadiness: No shaking, shifting or resetting during the hold. That suggests the effort was hard but manageable.
What to fix, in order of priority
Head position (the clearest issue). In the first few seconds your neck is extended and you're looking forward. By about 20 seconds your head has dropped and hangs below your shoulders, with your hair falling toward the mat, and it stays that way to the end. Aim for a neutral neck, with your eyes on the floor just ahead of your hands. Cue: "long neck, make a double chin."
Shoulders sinking (likely, less certain). In the second half your chest seems to sink between your shoulder blades. Cue: "push the floor away". Spread your upper back slightly while keeping your arms straight.
Late fatigue. In the last few seconds before your knees came down, your hips seem to settle a little lower. That's normal. Treat it as your signal to stop, not to grind through.
Next steps
Do 3 rounds of 35-40 seconds with perfect head and shoulder position, rather than chasing a longer time with your head hanging. Add 5 seconds per week.
Before every set: squeeze your glutes, brace your abs as if bracing for a light poke, and keep your neck long.
For a better review next time: put the phone exactly side-on at hip height (right now it's slightly low and angled). Then I can judge the hip line properly.
Two questions so I can tailor this:
Did you feel it mostly in your abs, or also in your lower back or shoulders?
Was 47 seconds close to your max, or did you have more left?
Sources: Livestrong - plank mistakes, Eat This - how to do a plank, NordicTrack - 5 common plank mistakes
Claude · Video 2 (hips higher) · Run 1
Tool activity: "Read 2 files, searched the web, ran 4 commands"
I looked at your whole hold: 47 seconds of video, checked with a full-body frame every 4 seconds and close-ups every 7 seconds. This is a high plank (arms straight), filmed from the side. That's a good angle for judging alignment.
What you're doing well
You held it about 40–44 seconds and your shape stayed the same. Your position at the start and near the end looks almost identical. Usually the first sign of tiring is the hips sagging or the body shaking, and I didn't see either. Your knees only dropped in the final seconds.
Your hands are under your shoulders, more or less. Your arms are close to vertical, which is the right setup for the wrists and shoulders.
Your legs are straight and active. Your knees aren't bending, and your feet are close together on your toes.
What needs fixing (most important first)
1. Your hips are too high. This is the main issue. From the side, your upper body is close to flat, but your legs slope steeply down from the hips to your heels. If you drew a straight line from your shoulder to your ankle, your hips would be clearly above it, in every frame. A raised hip like this moves work off the abs and onto the shoulders. It also makes the plank feel easier than it really is.
Fix: Lower your hips until shoulder, hip, knee and ankle are in one line. Squeeze your glutes and tuck your tailbone slightly, as if pulling your belt buckle toward your ribs. That tuck is what holds the hips in line without letting them sag.
Expect: Done properly, your hold time will probably drop at first. That's a good sign. It means your core is doing the work.
2. Your head is hanging down. Your head drops below your shoulders, and you're looking back toward your knees. That bends your neck forward and tends to round your upper back.
Fix: Look at the floor about 20–30 cm in front of your hands, so the back of your head lines up with your spine.
3. Your upper back may be sinking between your shoulder blades (a moderate-confidence call). Your shirt makes it hard to see, but your upper back looks a little sunk between your arms.
Fix: Push the floor away so your shoulder blades spread slightly and your upper back fills out. Your shoulders shouldn't be hanging off your arms.
One cue to use next time "Push the floor away, squeeze your glutes, eyes just past your fingertips." Those three actions fix all three issues together.
Something to try Film your next plank from the same angle. Before you start, put a broomstick along your back. In a good plank it touches your head, upper back and tailbone all at once. Then send me the video and I'll compare the two holds.
Quick question so I can tailor this: are you training for a target hold time, or for core strength in general? If it's strength, I'd suggest 3 rounds of about 20–30 seconds in perfect form instead of one long hold with the hips up.
Sources: NASM - The Plank: Coaching, Progressions and Variations · GoodLife Fitness - All About the Plank · Nike - Trainer-Approved Plank Variations
Claude · Video 2 (hips higher) · Run 2
Tool activity: "Read 2 files, ran 4 commands"
I watched your full 47-second clip frame by frame. It's a straight-arm (high) plank filmed from the side. Here's what I saw.
What you're doing well
You hold it steadily. Your position barely changes from about 2 seconds to 44 seconds. Your hips don't sag or drift as you tire, and that's the most common way a plank goes wrong.
Your arms are well set up. Your elbows are straight and your hands sit roughly under your shoulders, so the weight goes through your arm bones instead of your joints straining.
Your lower body is solid. Your legs are straight, your knees are locked and your heels sit over your toes.
You finished cleanly. At about 45 seconds you brought one knee forward and stepped out with control rather than collapsing. Ending on good form is the right instinct.
What to fix, most important first
Your head hangs down. This is the clearest issue. Your head drops below the line of your spine, and your face points back toward your knees instead of at the floor. It gets a little worse in the second half. Keep your neck long by looking at a spot on the floor just in front of your fingertips. Your ears should line up with your shoulders.
Your hips are slightly high. Picture a line from your shoulders to your ankles: your hips sit a bit above it. It's a mild pike, not a big fault, but it moves some of the work off your abs. To fix it, tuck your tailbone a little and squeeze your glutes. That flattens the line and usually makes the plank feel harder, which is how you know it's working.
Your upper back may be rounding (I'm less sure here). Your upper back looks a bit hunched between the shoulder blades. Try pushing the floor away firmly while keeping your chest from sinking or puffing up.
What I can't judge from this video: Your loose shirt hides your lower back and the exact position of your hips, and one side angle doesn't show whether your hips tilt or your hands are evenly spaced. Tight-fitting top, or one clip filmed from the front, would let me check those properly.
Verdict: Your base is good. The 45-second hold looked controlled throughout. Fix your neck first, since it's the easiest change. Once your hips line up, aim for clean holds of 30–45 seconds rather than longer ones. Coaching guidelines generally prefer several sets with good form over one long hold where form slips.
How did the last 10 seconds feel? If you felt it in your shoulders or lower back rather than your stomach, that tells me which of these fixes to focus on next. I'm happy to review a follow-up clip after you've tried the changes.
Claude · Video 2 (hips higher) · Run 3
Tool activity: "Read 2 files, searched the web, ran 3 commands"
Nice work. You held a full high plank for about 45 seconds with no break until you stepped out. I watched the whole clip frame by frame from the side. Here's what I saw.
What you're doing well
Arms are locked and stacked. Your elbows stay straight and your hands sit roughly under your shoulders. That's the right base.
Steady and controlled. No shaking, rocking or sagging at the low back. Your hips never dropped toward the floor, and that's the most common plank mistake.
Feet set well. They're about hip-width apart and you're up on your toes, which keeps you stable.
Clean exit. You stepped a knee through under control instead of collapsing.
What to fix
Your hips are too high (a slight pike). If I draw a line from your shoulders to your ankles, your hips sit above it. It was mild at the start and got bigger as you went on: by about 30 seconds, your hips had crept up noticeably. This is the body's way of handing work from your abs to your shoulders and hip flexors when the core gets tired. It's not dangerous, but it makes the exercise easier than it looks.
Cue: "Tuck your tailbone slightly and squeeze your glutes." That brings your hips down into line and switches your abs back on.
Your head is hanging. Your head drops below your arms, and your hair falls toward the floor, so you're looking back toward your hands or feet. That puts strain on your neck.
Cue: Look at a spot on the floor about 20–30 cm in front of your hands. Your ears should line up with your shoulders, so your neck carries on the line of your spine.
Push the floor away. Your upper back looks a little passive between the shoulder blades. Press actively through your palms so your upper back fills out slightly. That takes load off your shoulder joints.
Bottom line: the foundation is solid. Your main job is to stay in a straight line for the whole hold, especially in the second half when your hips start drifting up. A straight 30 seconds is worth more than a piked 45, so if your hips rise, it's fine to stop and reset rather than push through.
For your next video: set the camera at hip height (this one was low and angled slightly up), and wear a more fitted top if you can. Your loose shirt hid your spine and waistline, so I could judge the line but not finer details like low-back arching.
Would you like to send another attempt so I can compare? Also, what's your goal: longer holds, core strength for another sport, or general fitness? The answer changes how I'd progress you from here.
Sources: GoodLife Fitness - All about the plank · Fitness Volt - Proper plank form · Vitality - How to properly do planks
Gemini (3.1 Pro)
Gemini · Video 1 (hips lower) · Run 1
Video: 0:53
Here is an objective breakdown of your plank form:
What you are doing well:
Time: Great job holding the high plank for a solid 45 seconds!
Hand placement: Your hands appear to be stacked well underneath your shoulders, giving you a stable base.
Neck position: Your head and neck look relatively neutral. You are looking slightly down and forward rather than tucking your chin or craning your neck up.
Areas for improvement:
Sagging hips/Lower back arch: The most noticeable issue is that your hips are dipping towards the floor, which creates a pronounced arch in your lower back. This happens because your core isn't fully engaged to support your midsection.
How to correct it for next time:
Squeeze your glutes: Before you even lift your knees off the ground, squeeze your glute muscles. This naturally helps tilt your pelvis into the correct position.
Tuck your tailbone: Think about slightly tucking your tailbone under (a posterior pelvic tilt). This will help flatten out that arch in your lower back.
Brace your core: Imagine bracing for a punch in the stomach, or pulling your belly button up toward your spine.
Aim for a straight line: Your goal is to create a stiff, straight line from the back of your head, down through your upper back and hips, all the way to your heels.
Right now, your lower back is taking a lot of the strain. Focus on bracing your core to lift those hips up just a couple of inches until your back is flat!
Gemini · Video 1 (hips lower) · Run 2
Video: 0:53
Here is some feedback on your plank form:
Body alignment: Your hips are slightly too high. You want your body to form a straight line from your head to your heels. Try to lower your hips slightly to engage your core more effectively.
Hand placement: Your hands are placed well, directly under your shoulders.
Head position: Your head is in a good, neutral position, looking slightly ahead.
Overall, your form is decent, but bringing your hips down slightly will make the exercise more challenging and beneficial for your core. Keep practicing!
Gemini · Video 1 (hips lower) · Run 3
Video: 0:53
You held a solid plank for about 45 seconds!
Here is some feedback on your form:
Hips: Your hips are a bit high. Try to lower them so your body forms a straight line from your head to your heels. Engaging your core and squeezing your glutes will help with this.
Head/Neck: You are looking down at your hands, which is great. It keeps your neck in a neutral position.
Shoulders/Arms: Your shoulders are directly over your wrists, which is perfect for a high plank. You are pressing firmly into the floor, creating good stability.
Overall, great job! Focus on bringing those hips down slightly for a perfect straight-line plank. Keep up the good work!
Gemini · Video 2 (hips higher) · Run 1
Video: 0:47
Overall, you maintained a solid high plank position for approximately 43 seconds, which is a great effort! Here is some objective feedback based on the video:
Body Alignment: You kept a straight line from your head down to your heels for the vast majority of the time, which is excellent.
Hips: Your hips stayed level, avoiding the common mistakes of letting them sag or pushing them up toward the ceiling.
Neck and Head: Your neck was in a good, neutral position, as you were looking straight down at the floor between your hands.
Shoulders and Arms: Your shoulders appeared to be directly over your wrists, providing a stable base.
Keep up the good work! Maintaining that strong, neutral alignment is key to getting the most out of the exercise while protecting your lower back.
Gemini · Video 2 (hips higher) · Run 2
Video: 0:47
Based on the video, you maintained a solid high plank position for the majority of the time. Here's a breakdown of your form:
Body Alignment: Your head, back, and hips were well-aligned, forming a straight line from your head to your heels.
Arm Position: Your arms were straight, with your hands placed firmly on the ground beneath your shoulders.
Hip Placement: You did a good job of keeping your hips level, avoiding sagging or hiking them up too high.
Duration: You held the plank steadily from around 00:03 until you started to break form and lower your knees at 00:46.
Overall, it looks like you have a good grasp of the high plank technique! Keep up the good work.
Gemini · Video 2 (hips higher) · Run 3
Video: 0:47
Here is some feedback on your plank form:
Hips: Your hips are a little too high. Try to lower them so that your body forms a straight line from your head to your heels.
Back: You have a noticeable arch in your lower back. You should try to keep your back flat. Engaging your core and tucking your pelvis slightly can help with this.
You held the plank for about 45 seconds, which is a good effort! Keep practicing and focusing on your form.
ChatGPT (GPT-6)
ChatGPT · Video 1 (hips lower) · Run 1
I've reviewed your video. I'll assess your plank like a personal trainer would: body alignment, shoulder and hip position, stability, and how well you maintain form over time — not just how long you can hold it.
Your plank assessment
[image] 1. Body alignment — Good overall Your body forms a reasonably straight line from shoulders through hips to heels for much of the hold. Your hips stay fairly close to the height I'd want to see.
[image] 2. Shoulders and arms — Generally good You maintain a straight-arm plank with your hands planted firmly. Keep your shoulders stacked directly over your wrists, and actively push the floor away rather than letting your chest sink between your shoulders.
[image] 3. Head and neck — Needs attention Your head appears to hang down somewhat during the hold. Keep your neck in line with your spine and look at the floor a little ahead of your hands, without forcing your chin toward your chest.
[image] 4. Core control and endurance — Solid effort You maintain the position for most of the roughly 50-second recording. Your hips and torso show some movement, but the sampled frames don't show a dramatic loss of alignment. Tighten your abs and glutes to reduce small shifts.
Objective scorecard These are visual coaching estimates, not laboratory measurements.
Metric | Score |
Body alignment | 8/10 |
Shoulder stability | 7/10 |
Neck position | 6/10 |
Core and hip control | 7/10 |
Endurance | 8/10 |
Overall form | 7/10 |
Your hold duration Estimated continuous plank hold: ~47 seconds Based on the visible start and finish of the hold, excluding the rest of the recording. My verdict: A good baseline. Your next goal should be cleaner form, not simply a longer hold.
Three coaching cues for your next attempt
Brace: Tighten your abs as if preparing for a gentle punch, and squeeze your glutes.
Push: Press the floor away so your upper back stays active.
Align: Keep your ears, shoulders, hips and ankles in one line. Breathe normally throughout.
Stop the hold if you cannot maintain your position, or if you experience pain.
Your next training target For your next session, try 3 sets of 30–40 seconds, resting 45–60 seconds between sets. Prioritize consistent alignment over matching your previous duration.
One limitation: the camera angle lets me assess your overall side profile reasonably well, but it doesn't let me reliably measure left-to-right symmetry, wrist loading, or subtle pelvic rotation.
One question: During the final 10 seconds of this plank, how hard did it feel?
( ) 4/10 — Comfortable; I could have held much longer.
(•) 7/10 — Challenging, but my form was mostly controlled.
( ) 9/10 — Near my limit; I was struggling to maintain form.
( ) I felt pain or unusual discomfort.
[Submit answer]
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ChatGPT · Video 1 (hips lower) · Run 2
I've reviewed your plank video. I'll assess you like a personal trainer: focusing on body alignment, core and hip control, shoulder position, and how well you maintain form over time — not just how long you can hold the position.
Your plank assessment
[image] 1. Body alignment Your body appears reasonably straight overall in the sampled frames. Your hips are fairly close to the line between your shoulders and ankles. Keep your glutes engaged so your lower back doesn't gradually sag.
[image] 2. Shoulder and arm position You're performing a high plank on your hands. Keep your hands planted, wrists approximately beneath your shoulders, and elbows extended without forcefully locking them. Push the floor away rather than sinking between your shoulders.
[image] 3. Head and neck Keep your neck neutral and gaze at the floor slightly ahead of your hands. Avoid lifting your head to look forward or letting it hang excessively.
Objective scorecard (shown as bar ratings)
Overall body alignment: Good
Hip stability: Good
Shoulder positioning: Needs closer view
Neck position: Needs closer view
Endurance: Strong effort
Provisional visual ratings, not instrumented measurements. The camera is relatively far away, so small alignment errors and muscle fatigue are difficult to verify.
My trainer's verdict Your biggest opportunity is consistency, not simply increasing hold time.
Your video lasts approximately 53 seconds, and you maintain a high-plank position for most of it. That's a useful endurance effort. However, video duration alone doesn't establish 53 seconds of perfect-form holding, and I can't objectively measure core activation or fatigue from appearance alone.
For your next attempt, focus on these three cues:
Brace: Tighten your abdomen as if preparing for a gentle punch.
Squeeze: Engage your glutes and keep your ribs from flaring.
Stay still: Keep your shoulders, hips, and ankles aligned without letting your lower back sag.
End the hold when you can no longer maintain good form, rather than pushing through with a compromised position. Stop if you experience pain, especially in your lower back or wrists.
Your next training target I'd use 3 sets of 30–40 seconds, resting 45–60 seconds between sets, if you can maintain good form throughout. Once all three sets look controlled, progress gradually toward longer holds.
For more precise feedback next time, position your camera at hip height, perpendicular to your body, with your entire body visible from the side. That will make hip position, spinal alignment, and changes in posture much easier to assess.
One question so I can coach you more effectively: Are you training for core strength, visible abs, general fitness, or improving your maximum plank time?
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ChatGPT · Video 1 (hips lower) · Run 3
I've reviewed your video. I'll coach you like a personal trainer: focusing on body alignment, core stability, shoulder position, hip control, and how long you can hold the position with good form — not just how long you can endure it.
One important distinction: your video shows a high plank (straight arms), rather than a forearm plank. Both are excellent exercises, but I'll assess your technique for the variation you're actually performing.
Your plank assessment
Estimated hold: ~45 sec (Approximately 4s–49s in the video)
Technique: Good (From the visible side view)
Form scorecard Visual assessment only — these are coaching estimates, not laboratory measurements.
Body alignment — 4/5 Your torso and legs remain reasonably aligned throughout most of the hold. Keep the hips level rather than allowing them to sink or rise.
Shoulders and arms — 4/5 Your arms appear straight and your hands are positioned reasonably beneath your shoulders. Keep pushing the floor away so your upper back stays active.
Head and neck — 3.5/5 Your head appears slightly lowered. Keep your neck in line with your spine and look at the floor just ahead of your hands.
Hip and core control — 3.5/5 Your position looks fairly steady, though subtle pelvic movement is difficult to judge at this camera angle. Squeeze your glutes and gently draw your ribs toward your pelvis.
My three coaching cues for your next attempt
[image] 1. Create one straight line Imagine a straight line from the back of your head through your shoulders, hips and ankles. Avoid arching your lower back.
[image] 2. Actively push the floor away Keep your shoulders stable, arms straight and shoulder blades controlled. Don't simply hang between your shoulders.
[image] 3. Brace and breathe Tighten your abdomen as if preparing for a gentle punch, squeeze your glutes, and continue breathing normally. Stop when you can no longer maintain your position.
Your next training target Based on this clip, I'd use a controlled 40–45-second high plank as your starting benchmark rather than immediately chasing a longer hold.
Set 1: 30–40 seconds, concentrating on perfect alignment.
Set 2: 30–40 seconds after 45–60 seconds of rest.
Progression: Once both sets look controlled, add 5 seconds at a time.
Stop if you experience sharp pain, especially in your lower back or shoulders.
Let's make the feedback more objective For future videos, use the same side-view camera angle and record your entire hold. I can compare your alignment at the beginning, middle and end, estimate your hold duration, and identify visible changes in technique. A single side view cannot reliably measure muscle activation or diagnose problems.
One question before I set your training benchmark:
What's your main goal?
(•) Improve technique and core stability
( ) Hold a plank for longer
( ) Build overall core strength
( ) All three
Which plank do you want me to assess?
(•) High plank (straight arms, as in this video)
( ) Forearm plank (elbows on the floor)
( ) Both variations
[Set my training focus]
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ChatGPT · Video 2 (hips higher) · Run 1
I've reviewed your 47-second video. I'll assess your plank like a personal trainer: focusing on visible technique, body alignment, stability, and endurance—not just how long you can hold it.
Your plank assessment
47.1 seconds recorded Your video lasts 47.1 seconds, and you maintain a high plank on your hands for most of the clip. This is a useful baseline for tracking your progress.
1. Body alignment — generally good Your shoulders, hips, and legs appear reasonably aligned in the side view. I don't see an obvious, pronounced sag through your lower back. Your hips look fairly level, although the camera angle and clothing limit precision.
2. Shoulder and arm position — good foundation Your hands are planted beneath approximately the shoulder area, with your arms extended. Keep your hands firmly grounded and push the floor away so your upper back stays active rather than sinking between your shoulders.
3. Core and pelvic control — your main focus Aim to gently tuck your pelvis, tighten your glutes, and brace your abdomen as if preparing for a light punch. Your overall shape looks promising, but a still image cannot confirm how effectively you're maintaining abdominal tension or controlling your lower back under fatigue.
4. Head and neck — small refinement Your head appears slightly lowered, which is generally appropriate. Keep your neck relaxed and gaze at the floor a little ahead of your hands, rather than lifting your chin or forcing your head down.
My coaching verdict
Technique snapshot — Promising form Based on what is visible in this recording, not a clinical assessment.
Body-line consistency | Good |
Arm positioning | Good foundation |
Core engagement | Needs confirmation |
Endurance baseline | 47 seconds |
I wouldn't yet call this a full 47 seconds of verified, strict-form endurance. The recording looks relatively stable, but I can't reliably measure subtle changes in hip height, breathing, or muscle fatigue from this camera angle.
Your next plank: three coaching cues
Brace: tighten your abdomen and glutes before you start the timer.
Align: keep your shoulders over your wrists, ribs controlled, and body in one long line.
Breathe: exhale normally instead of holding your breath. End the set when you can no longer maintain good form, or if you feel pain.
For your next attempt, aim for 40–45 seconds of deliberate, controlled form rather than chasing a longer time. If you maintain that form comfortably, we can progress gradually.
Let's make this objective One question before I set your training targets:
What is your main goal with planks?
(•) Build core strength and stability
( ) Improve abdominal definition
( ) Hold a plank for longer
( ) Improve posture and lower-back support
How often do you currently train?
( ) Just starting out
(•) A few times per week
( ) Regularly and consistently
[Set my training targets]
Once I know your goal, I can help you track hold time, form quality, and progress across future videos.
ChatGPT · Video 2 (hips higher) · Run 2
I've reviewed your plank video. I'll assess you like a personal trainer: form first, endurance second, and measurable progress over time. I'll distinguish what I can actually see in the video from what I can't reliably assess from a single camera angle.
Your plank assessment
Duration: 47.1 seconds Video length; your actual hold may be slightly shorter if setup or transitions are included.
Body alignment — Generally good Your body appears relatively straight from shoulders through hips toward heels, and you maintain a fairly consistent position across the sampled frames.
Stability and endurance You sustain the position throughout most or all of the clip without an obvious major collapse in the sampled frames. That is encouraging, although small changes in muscle tension and breathing aren't measurable from these images.
What I'd focus on next
[image] 1. Lock in your core Gently tuck your pelvis, brace as if preparing for a light punch, and keep your ribs from flaring. This helps prevent your lower back from arching as you fatigue.
[image] 2. Keep your shoulders stable For your high plank, aim to keep your shoulders over your wrists, spread your fingers, and actively push the floor away.
[image] 3. Maintain breathing Breathe steadily rather than holding your breath. Keep your neck neutral and your glutes engaged throughout the hold.
These are technique cues to refine, not claims that you are doing all three incorrectly. Your video is a little distant, so I can't confidently measure your spinal position or shoulder and hip angles.
Your baseline scorecard
Metric | Assessment |
Hold duration | Approximately 47 seconds of video |
Alignment | Generally straight |
Consistency | Appears stable |
Breathing quality | Not reliably assessable |
Overall form | Promising; closer footage needed for precise scoring |
Your next workout I'd rather see you hold a clean plank for 30–40 seconds than force a longer hold with compromised form.
Set 1: 30–40 seconds, strict technique.
Set 2: 30–40 seconds, resting 60–90 seconds between sets.
Set 3: Optional, only if your form remains solid.
Stop the set if your hips sag, your lower back starts to arch, or you experience pain.
For your next recording, place the camera closer to you at hip height, directly from the side, with your whole body visible. That will let me evaluate alignment much more accurately.
One question so I can coach you consistently: Is your main goal to hold a plank for as long as possible, build core strength, or improve your overall physique and fitness?
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ChatGPT · Video 2 (hips higher) · Run 3
I'll act as your personal trainer and assess your plank using visible technique markers, not just how long you can hold it. I'll focus on body alignment, shoulder and hip position, core control, and whether your form changes as you fatigue.
For a fair assessment, I'll distinguish what I can clearly see in your video from what the camera angle makes difficult to judge.
Your plank assessment
Visible hold duration: 47.1 sec (Continuous video; already in position at the start)
Technique rating: 7.5/10 (Provisional visual assessment)
1. What you're doing well
✓ Shoulder and arm stability: Your arms remain extended, and your shoulders appear reasonably well positioned over your wrists.
✓ Hip and torso control: Your trunk appears fairly stable throughout the sampled frames. I don't see an obvious, pronounced collapse of your lower back.
✓ Consistency: Your overall position looks similar from the beginning through the end of the recording, with no obvious major breakdown in the sampled frames.
2. What to improve
◎ Keep your hips in line with your shoulders and heels: Your hips appear slightly elevated. This isn't a major fault, but aim for a straighter line from shoulders through hips to ankles. Avoid both lifting your hips and letting them sag.
◎ Brace actively rather than simply holding still: Gently tighten your abdomen as if preparing for a light punch, squeeze your glutes, and keep breathing normally. These actions can't be verified from the video, so treat them as technique cues.
◎ Keep your neck neutral: Your head is angled downward and your hair obscures your neck. Keep your gaze on the floor just ahead of your hands without letting your head hang.
3. Your next training target Don't chase a longer hold at the expense of technique. Your next goal is 45–50 seconds with deliberate, consistent form.
Next-session protocol
Set 1 — 35 seconds: Focus on a straight body line and active bracing.
Rest — 45–60 seconds: Recover fully and breathe normally.
Set 2 — 35 seconds: Repeat the same standard without letting your hips drift.
Stop the set if you cannot maintain alignment, or if you experience pain. Build duration only when your technique remains consistent.
4. How we'll measure your progress I'll use the same criteria each time you send a video:
Metric | What I'll look for |
Body alignment | Shoulders, hips and ankles form a relatively straight line |
Shoulder position | Shoulders remain stable over or near the wrists |
Hip control | No obvious sagging or excessive elevation |
Neck position | Head stays in line with the torso |
Endurance | Time maintained with acceptable technique |
Fatigue | Any visible change in form near the end |
One limitation: this is a single side-view recording, so I can't reliably assess your breathing, internal core engagement, or subtle rotation toward or away from the camera. The numerical score is a coaching estimate, not a clinical measurement.
My verdict: You have a solid starting point. The biggest opportunity is refining your hip alignment and maintaining active tension throughout the hold, rather than simply trying to beat your time.
One question so I can tailor your training: What's your main goal with planks?
(•) Stronger core and better stability
( ) Hold a plank for 1–3 minutes
( ) Build visible abdominal definition
( ) Improve posture and lower-back support
Do you experience any pain during planks?
(•) No pain
( ) Wrist or shoulder discomfort
( ) Lower-back discomfort
( ) Other pain
[Personalize my training]
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