Trunk-extensor endurance (Biering-Sørensen) + McGill torso-balance ratio screen — Waterloo, Ontario, Canada.

Waterloo, Ontario is home to the University of Waterloo, where Stuart McGill -- Distinguished Professor Emeritus of Spine Biomechanics, whose 1999 torso endurance battery and normative flexor:extensor / side-bridge:extensor ratios this standard applies -- built his research program. A distinct connection from this library's existing Los Angeles tile, which is built on that city's own construction/trades workforce loading pattern rather than the instrument's academic origin.

Where

Workforce / workplace programs, Waterloo, Ontario, Canada (confidential; self/partner-administered with coached guidance) · Open the map

Pay

$220 proposed

This packet is not funded yet, so this figure is a proposed price and not money waiting in escrow. If a buyer funds it, approved proof settles that price onchain. If nobody funds it, approved proof earns provable credit toward the work instead of cash — recorded, and readable any time at vealth.net/labor/credit/(your wallet). You see which before you claim, never after.

Proof

pre-test back-pain/red-flag screen (cleared, or routed and the test not performed) + Biering-Sørensen extensor hold time + McGill flexor and left/right side-bridge hold times + computed flexor:extensor and side-bridge:extensor ratios and left:right symmetry, with any red flag, pain-triggered stop, or high-risk ratio pattern routed to a clinician or physical therapist and a ratio-targeted training plan recorded for those cleared

This is exactly what gets it approved. Nothing settles without it.

Level

intermediate

Open until

2026-12-31

Posted by

0x034F…6c89

The creator wallet. Its signature is what approves proof and settles the wage.

How this work is done

A documented method, so this packet comes out the same whoever does it.

Bring

• a padded table or plinth with the edge at iliac-crest height (or a Biering-Sørensen test bench)
• straps, or an assistant/partner, to fix the pelvis, legs, and ankles to the table
• stopwatch/timer
• a firm mat for the side-bridge and curl-up holds
• a pre-test back-pain / red-flag screening checklist
• a secure note for hold times, computed ratios, and referrals

Steps

1. 1. Screen for back pain and red flags FIRST, before any positioning: current low-back pain of any intensity, sciatica or radiating leg pain/numbness, a back injury within the past 6 weeks, unexplained weight loss, fever, saddle numbness, new bowel/bladder change, prior spinal fracture/surgery, or uncontrolled disease -> STOP, do not test, route to a clinician or physical therapist. This is a screen for pain-free people, never a diagnostic tool to push through pain.
2. 2. For those cleared: demonstrate all three holds (prone extensor, flexed-knee flexor curl-up, side bridge) before timing anything, and confirm the person can reach each position pain-free.
3. 3. Biering-Sørensen extensor hold: position prone with the upper body (from the iliac crest up) unsupported off the table edge, arms crossed over the chest, pelvis/legs/ankles fixed by straps or a spotter; hold the torso horizontal, in line with the legs, and time to failure (loss of the horizontal position) or a 240-second cap. Stop immediately on pain.
4. 4. McGill trunk-flexor hold: supine, knees bent ~90 degrees, trunk flexed to ~60 degrees (shoulders off the floor, resting against a wedge or the tester's hands at that angle), arms across the chest; time to failure (loss of the 60-degree position) or a 240-second cap. Stop immediately on pain.
5. 5. McGill side-bridge holds, both sides: side-lying on the forearm and feet (top foot ahead of the bottom foot for stability), hips lifted off the floor into a straight line, free arm across the chest; time each side to failure (hips touch down) or a 240-second cap, with full rest between sides. Stop immediately on pain.
6. 6. Compute the ratios: flexor:extensor (McGill's normative target is below ~1.0 — an extensor hold notably shorter than the flexor hold is the injury-risk pattern) and each side-bridge:extensor (target below ~0.75), plus the left:right side-bridge ratio (target close to 1.0, symmetric).
7. 7. Record all four raw hold times, both ratios, and side-to-side symmetry; compare against McGill's normative bands as a risk-pattern signal, never a diagnosis.
8. 8. Coach a ratio-targeted endurance/bracing plan (McGill's 'big three': curl-up, side bridge, bird-dog) sized to the weakest link identified by the ratios, sign, and set a retest cadence.

What counts as done

• Pre-test back-pain/red-flag screen completed and recorded BEFORE any positioning; any positive flag routes to a clinician or physical therapist and the test is not performed
• All four hold times recorded (Biering-Sørensen extensor, McGill flexor curl-up, side-bridge left, side-bridge right) with the stop reason for each
• Flexor:extensor and side-bridge:extensor ratios computed and compared to McGill's normative targets, plus left:right side-bridge symmetry, as a risk-pattern signal, not a diagnosis
• A ratio-targeted McGill 'big three' training plan recorded, sized to the weakest link identified (job-loading pattern noted: lifting, carrying, overhead work), plus a retest date

Proof is measured against these, not judged by taste.