Lockin

Build → 100 leg raises a day

100 leg raises a day, every day, with money on the line.

Distribute reps across the day in short submaximal sets. Lockin's on-device pose detection counts each valid rep. Hit your daily target and your stake returns. Miss and your stake funds the charity you chose. Most users start at 30 or 50 a day and build up.

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Suggested starting contract

$5/day against missing your daily target of 100 leg raises.

Why willpower fails to start this

The 100-leg-raises-a-day target is harder than it looks on paper, and the failure mode usually has nothing to do with abdominal strength. Leg raises load the iliopsoas and rectus femoris far more than they load the rectus abdominis — a point made repeatedly in the strength-and-conditioning literature, including the NSCA's "Essentials of Strength Training and Conditioning" and Mike Boyle's "New Functional Training for Sports" (Human Kinetics, 2016). The hip flexors are short, deep, and habitually tight in anyone who sits for a living. Add a long sedentary workday on top of a tight psoas, and a hundred reps in a single session is not just unpleasant — it is biomechanically a poor idea, especially if the legs are kept straight throughout. This is why most people abandon the goal: they try all 100 in one set, the lower back lights up before rep 40, and the conclusion is "I'm not strong enough" when the actual conclusion should be "the structure was wrong." Stuart McGill, PhD, professor emeritus of spine biomechanics at the University of Waterloo and author of "Back Mechanic" and "Ultimate Back Fitness and Performance," has spent decades documenting how lying straight-leg raises load the lumbar spine. Each rep applies meaningful compressive and shear force to the lower-back disks, and that load compounds across high rep counts in a single session. McGill's "Big Three" — bird-dog, side plank, and the McGill curl-up — were designed precisely because traditional flexion-heavy core work, including aggressive straight-leg raises, tends to aggravate the lumbar tissues it is supposed to support. His framework does not say avoid leg raises. It says spread the volume, allow knee bend where the lower back complains, and respect the spine's tolerance for any given session. A grease-the-groove structure — small, frequent, distributed sets — fits that prescription almost exactly. Pavel Tsatsouline formalized that distribution in "The Naked Warrior" (Dragon Door, 2003): submaximal repeated practice across the day builds the motor pattern without the systemic fatigue cost of training to failure. Brad Schoenfeld's 2016 and 2017 meta-analyses on volume distribution found that splitting weekly volume across more sessions produces adaptation at least as efficiently as concentrating it, and often more so for novice and intermediate trainees. The strength side of the case is settled. The behavioral side is not. Greasing the groove for leg raises means lying down on the floor at five or six odd moments through the day, which feels small, unrewarding, and skippable in isolation. Kahneman and Tversky's prospect theory (Econometrica, 1979) identified the lever that closes that gap: losses register roughly twice as intensely as equivalent gains. A $5 stake on today's contract behaves closer to $10 of avoidance pressure at 9pm, when the rationalization to skip the last set is loudest. That asymmetry is exactly what tips the decision toward the floor.

How Lockin verifies it

Lockin verifies leg-raise completions using on-device pose detection. Because you perform leg raises lying supine on the floor, you place your phone face-up on the floor beside you so the front camera can see your body from the side. The camera feeds into a real-time pose-estimation model that runs locally on the device — no video is uploaded or stored. The model tracks key landmarks (hip, knee, and shoulder positions) with a visibility threshold of at least 0.5, then evaluates a midpoint angle on each rep. A rep registers as valid when the angle drops below roughly 110 degrees in the up/raised state and returns above roughly 160 degrees in the down/flat state. Partial reps that never break the threshold do not count. The on-screen counter updates live so you can see your tally as you go. Each completed set appends to your daily total. You can run as many separate sets through the day as you want — the app accumulates verified reps toward the daily target. Reps performed without the camera-tracked session running do not count. Because the highest single-set value in the reps menu is 30, a 100-a-day target naturally splits across multiple sessions: ten sets of ten, five sets of twenty, four sets of twenty-five, or any combination you build in the wizard. The day clears once your verified count crosses the target before your daily deadline in your local timezone.

Set up a 100 leg raises a day contract in 5 minutes

  1. 1

    Install Lockin

    Free download on the App Store and Google Play. Account creation takes under a minute using email or Apple/Google sign-in.

  2. 2

    Choose the Workout Pose challenge type

    Select Workout Pose from the challenge picker, then select Leg Raises as your exercise. This activates on-device pose detection tuned for the supine leg-raise movement — the model evaluates a midpoint angle on each rep rather than a top-and-bottom landmark distance.

  3. 3

    Set your daily target honestly

    100 leg raises a day is a heavy target — leg raises are harder per rep than pushups for most users because the hip flexors fatigue quickly and the lower back accumulates load. Start at 30 or 50 reps a day for your first 20-day contract if you are not already training core daily. Once a 30 or 50 floor feels routine across a full contract, raise to 75 for the next contract, then 100. Building from a sustainable base prevents the contract from becoming a lower-back injury risk.

  4. 4

    Set your daily deadline

    By default the deadline is end-of-day — 23:59 in your local timezone — so your verified reps need to be logged before midnight. Tap Set deadline in the wizard to pick an earlier time on a 24-hour picker; 9:00pm works well for the leg-raise challenge because the floor work is much easier to skip at the end of the day, when bedtime momentum builds. An earlier deadline raises both the difficulty and the reward: tighter deadlines unlock higher Locks and XP rewards. The deadline is set once during contract creation and applies to every scheduled day for the life of the contract — it cannot be edited mid-contract.

  5. 5

    Set your stake and choose your charity

    The default stake is $5 per day — enough that skipping the last set at 9pm registers as a real cost, not a rounding error. Then select from Lockin's vetted charity list across categories including climate, mental health, animal welfare, and digital literacy; if you miss your daily target, your stake funds that cause. Lockin charges a small platform fee to cover payment processing and operations.

  6. 6

    Plan your sets in advance

    Decide in writing when each set will happen — five sets of ten before lunch, dinner, an evening break, etc. — rather than leaving it to spontaneous willpower. Greasing the groove only works when the sets are scheduled to specific cues; otherwise the day collapses into one rushed session at 10pm, which is exactly the structure McGill's research warns against.

  7. 7

    Confirm and lock in

    Your stake is held securely by Stripe. Complete your verified reps before your daily deadline in your local timezone each day for your contract to clear. Your first workout-pose contract is free; subsequent contracts in this category require a Premium subscription.

From Lockin's data

In the Lockin beta, workout-pose users who set realistic starting floors — 30 or 50 reps per day for a first leg-raise contract — completed their first 20-day cycle at meaningfully higher rates than users who chose 100 cold. Users who distributed reps across four or more separate sets across the day reported less lower-back discomfort than users attempting large single-session efforts, consistent with Stuart McGill's framework on cumulative spinal load.

"I kept trying 100 in one go and my lower back would be wrecked by day three. Started over at 50 a day with bent knees, ten reps five times across the day, and finished my first 20-day contract clean. Just upgraded to 75 for the second cycle. The $5 was the only reason I bothered with the 4pm set on a slow Tuesday."

— Anonymous beta user, leg-raise challenge, 7 weeks active

Common questions

Does the rep count if I bend my knees instead of keeping my legs straight? +

Yes. Lockin's leg-raise model evaluates a midpoint angle on each rep — the angle drops below roughly 110 degrees in the up/raised state and returns above roughly 160 degrees in the down/flat state — and that threshold check works for both straight-leg and bent-knee variations. Bent-knee leg raises (sometimes called reverse crunches or knee tucks) are explicitly easier on the lumbar spine than straight-leg raises, because the shorter lever arm reduces the load on the lower back. Stuart McGill's spine-biomechanics work at the University of Waterloo argues for exactly this kind of regression when the lower back is sensitive: keep the movement, reduce the lever, accumulate the volume safely. The app does not penalize knee bend, so feel free to start bent-knee, progress to straight-leg as your hip flexors and core strengthen, or alternate within a session.

Are 100 leg raises a day actually safe for my lower back? +

It depends on your starting point and how the volume is distributed. Stuart McGill, PhD, professor emeritus at the University of Waterloo and author of 'Back Mechanic,' has documented that lying straight-leg raises apply meaningful compressive and shear force to the lumbar disks, and that load compounds across high single-session rep counts. The way to make a 100-a-day target safer is to spread the volume across the day in small sets — grease-the-groove style — so no single session accumulates the kind of cumulative load McGill warns about. Bent-knee variations reduce the lever arm and substantially lower the lumbar load. If you are returning from a back issue, start with a 30 or 40 daily floor and bent knees, build to 50 for a second contract, and only progress to straight-leg or 100 reps once the lower back tolerates the volume cleanly. The stake is what enforces consistency; the structure is what protects the spine.

Where does the forfeited money actually go? +

Forfeited stakes go to a registered charity from Lockin's vetted list. You choose the charity from categories including climate, mental health, animal welfare, and digital literacy when you set up the contract. The bulk of your stake funds the charity you chose if you miss a day. Lockin charges a small platform fee to cover payment processing and operations. Refer to the transparency page inside the app for charity-by-charity tallies.

How does the daily deadline work, and can I change it after I start the contract? +

Every contract has a per-day deadline by which your prescribed reps must be completed in a camera-tracked session. The default is end-of-day — 23:59 in your local timezone — so the day clears any time your verified count crosses your target before midnight. During the 7-step contract wizard you can tap Set deadline and pick any earlier time on a 24-hour picker; 9:00pm is a strong choice for the leg-raise challenge because floor work tends to die in the bedtime window. The deadline you set applies to every scheduled day for the life of the contract. Tighter deadlines unlock higher Locks and XP rewards. The deadline is locked in at contract creation and cannot be edited mid-contract — that immutability is what makes it function as a precommitment rather than a movable target.

Other habits people build

Stop deciding. Start staking.

Free to download. You set the target, the stake, and the charity.

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Author

The Lockin Team — Lockin Editorial

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