reckonerBird dog
On all fours, one arm forward and the opposite leg back, hips square throughout. It is the least dramatic movement in the library and one of the most useful, because the point is not the reach. The point is everything that does not move while you reach.
Reach long, keep the hips square.
- Pattern
- Core anti-extension
- Trains
- Abs, spinal erectors, glutes
- Kit
- Bodyweight, floor
- Loading
- Your own bodyweight
- Reckoner prescribes
- 3 sets of 8 to 12 reps at RPE 8
- Progression step
- Nothing to add, so the sets climb instead
- Skill
- Simple to learn
- Recovery cost
- Very low
Muscles worked
How to do it
Set the base
Hands under the shoulders, knees under the hips, back flat and neck long. Push the floor away slightly so the shoulder blades sit against the ribcage rather than pinching together.
Brace before anything leaves the floor
Tighten the belly as if you were about to be prodded in it, and squeeze the glutes. Everything after this is about holding this position while a limb moves.
Reach one arm and the opposite leg
Slide the arm forward and the leg back until both are roughly level with your body. No higher. Lifting the leg above the hip arches the back, which is the one thing this movement exists to prevent.
Come back under control and swap
Return the hand and the knee to the floor without letting the weight dump onto them, then do the other side. Both sides together are one rep, and the set ends when the hips start to tip rather than when the count runs out.
What goes wrong
The hip on the moving side rolling open
It happens the moment the leg goes back and it is almost invisible from the inside. The lift feels bigger because it is, and the extra height came from turning the pelvis rather than from extending the hip.
Reaching high instead of long
Height looks like effort, so the arm and the leg climb. What that does is arch the back and hand the work to the lower back muscles. Reach for the wall in front of you and the wall behind you, not for the ceiling.
Rushing it
This is a slow movement done badly at speed. Momentum from a fast swap carries the limb up and the trunk never has to hold anything still, which is the whole exercise gone.
How Reckoner progresses this lift
Six weeks of this lift, run through the real engine. Nothing below was typed in: the prescription, the decision and the sentence beside it all come from the same code that writes your week.
| Week | Prescribed | What it did |
|---|---|---|
| 1 | 3 x 8 | More reps 8 → 9 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. |
| 2 | 3 x 9 | More reps 9 → 10 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. |
| 3 | 3 x 10 | More reps 10 → 11 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. |
| 4 | 3 x 11 | More reps 11 → 12 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. |
| 5 | 3 x 12 | Deload 40% of sets offFive weeks of building, then one week lighter. About 40% of the sets come off. The load holds and your reps stay where you earned them, so you keep the strength and lose the fatigue. |
| 6 | 2 x 12 | One more set 2 → 4 setsYou hit the top of the range at RPE 7 and there is no weight left to add. When a lift runs out of load, the set is the increment, so it does four sets next week. |
Real engine output, not an illustration. Every row was produced by running the engine itself when this page was generated.
The full rule, and why the reps move before the load does, is in how Reckoner decides to add weight.
Questions people ask
Why bother with an arm and a leg at once?
Because the pair is what makes it hard. In people with chronic low back pain, the opposing arm and leg version produced significantly more multifidus and lumbar iliocostalis activity on both sides than raising an arm alone or a leg alone1. One limb is the regression, not the exercise.
Will this build muscle?
Not much, and it is honest to say so. Measured against eight other bodyweight exercises, the quadruped arm and leg lift passed the threshold usually taken as a strengthening stimulus only at the gluteus maximus, and sat below it everywhere else2. It trains endurance and control of position, which is a different job from growing a muscle.
Does this help a bad back?
Trunk-focused exercise does beat doing nothing for chronic low back pain, and beats general exercise by a small margin on both pain and disability3. That is a modest, real effect rather than a cure, and this movement is one item inside that category rather than a treatment on its own.
Similar movements
There is no load to ease on this lift, so Reckoner offers one of these the first time it stalls. Each of them has a page.
Sources
- Yoon and colleagues, Physiotherapy Research International, 2015. Trunk muscle activation during different quadruped stabilization exercises in individuals with chronic low back pain ten people with chronic low back pain compared on the quadruped arm raise, leg raise and opposing arm and leg raise, where the opposing version produced significantly greater multifidus and lumbar iliocostalis activity on both sides than either single limb version
- Ekstrom, Donatelli and Carp, Journal of Orthopaedic and Sports Physical Therapy, 2007. Electromyographic analysis of core trunk, hip, and thigh muscles during 9 rehabilitation exercises thirty healthy adults across nine bodyweight exercises, where the side bridge was one of only three to pass 45 per cent of a maximal contraction, at the gluteus medius and the external oblique, and the quadruped arm and leg lift did so at the gluteus maximus, with every other exercise below that line and therefore better suited to endurance than to strength
- Prat-Luri and colleagues, Journal of Orthopaedic and Sports Physical Therapy, 2023. Effect of trunk-focused exercises on pain, disability, quality of life, and trunk physical fitness in low back pain and how potential effect modifiers modulate their effects: a systematic review with meta-analyses forty randomized controlled trials and 2391 participants, where trunk-focused exercise beat doing nothing on every outcome but beat general exercise only by a small margin on pain and on disability, a standardized mean difference of 0.20 for each