2018 — Upper vs Lower Lumbar Spine Kinematics in Fast Bowling

Research theme

Lumbar stress fracture is the most serious injury a fast bowler suffers, and “too much lumbar movement” has long been blamed. But almost every motion-analysis study up to this point treated the lumbar spine as one rigid segment from L1 to L5. The lumbar spine is five vertebrae with facet joints between each — it does not move as one block. This study asked a simple methodological question: if you split the lumbar spine into an upper segment (L1–L3) and a lower segment (L3–L5), do they actually move differently during a delivery?

Method: 20 elite male fast bowlers (age 19.32 ± 2.33 years; height 1.88 ± 0.06 m; mass 83.00 ± 6.50 kg; max ball velocity 35.02 ± 1.74 m/s), three overs of maximal-effort bowling each, captured by an 18-camera VICON MX system at 300 Hz. Reflective markers were placed to define separate upper and lower lumbar segments (marker scheme adapted from Seay et al., 2008). The fastest delivery per bowler was analysed. Comparison by Wilcoxon signed-rank test.

What they measured

• How much the upper back-of-the-lumbar-spine bends versus the lower (upper L1–L3 vs lower L3–L5 joint angles), in all three planes.
• Bending forward / arching back (sagittal plane: flexion / extension).
• Leaning sideways away from the bowling arm, and towards it (frontal plane: contralateral / ipsilateral side flexion).
• Twisting (transverse plane: ipsilateral / contralateral rotation).
• Each measured at four moments: back foot contact (BFC), front foot contact (FFC), ball release (BR), and the maximum value during the delivery.

Findings

All numbers below are mean differences between the two segments ± SD, i.e. how much more one segment did than the other. All were statistically significant with moderate-to-large effect sizes (P < 0.05, r > 0.50).

1. Sagittal plane — the lower lumbar spine bends forward more. Lower segment showed greater flexion than the upper at BFC (12 ± 10°), at BR (6 ± 6°), and at maximum (5 ± 8°).
2. Sagittal plane — the upper lumbar spine arches back more. The lower segment showed 7 ± 9° less maximum extension than the upper.
3. Frontal plane — the lower lumbar spine does most of the sideways lean away from the bowling arm. Lower segment showed greater maximum contralateral side flexion (8 ± 10°) and greater contralateral side flexion at FFC (13 ± 9°) — the largest single difference in the study, and it occurs at front foot contact, exactly when ground reaction forces peak.
4. Frontal plane — the upper lumbar spine does more of the lean towards the bowling arm. Lower segment showed 4 ± 7° less maximum ipsilateral side flexion.
5. Transverse plane — twisting is mostly an upper-lumbar job. Ipsilateral rotation was greater in the upper segment at FFC (6 ± 6°), at BR (3 ± 6°), and at maximum (7 ± 6°).

Interpretation the authors draw: the upper lumbar spine contributes most of the extension, ipsilateral side flexion and rotation; the lower lumbar spine contributes most of the flexion and contralateral side flexion. Since lumbar stress fractures overwhelmingly occur at L4/L5 on the contralateral side, and the lower segment is the one doing the contralateral side flexion, this is a plausible mechanical link.

All of this is descriptive/correlational. No injured group was studied here. The paper explicitly calls for a follow-up comparing injured to uninjured bowlers — which became the 2020 ISBS paper and the 2021 MSSE paper in this same cluster.

What a coach should look for on video

Be honest about what this paper can and cannot give you. This is a measurement-methods study on 20 uninjured bowlers. It supports no injury-prevention cue by itself. What it gives a coach is a way of looking — and one specific place to look.

Cue 1 — Look at the low back separately from the mid back.

• The cue: Do not judge “trunk lean” as one thing. Split your eye between the region just above the belt line (lower lumbar, roughly L3–L5) and the region between the bottom of the ribs and the middle of the low back (upper lumbar, roughly L1–L3). They are doing genuinely different jobs.
• Camera view + frame: Front-on (or behind-the-arm), scrubbed to front foot contact. Front-on is essential — sideways lean is invisible side-on.
• What “good” looks like: No threshold is available from this paper. What you should see is that the sideways lean away from the bowling arm is distributed — the mid-back is contributing, not just a sharp hinge at the belt line.
• What the fault looks like: A sharp kink low down — the pelvis stays relatively level while the spine snaps sideways at one point just above the waistband, with the ribcage riding along as a rigid block above it. That is the lower lumbar segment doing all the work.
• Why it matters: The lower segment is where fractures happen (L4/L5, contralateral side) and this paper shows the lower segment already contributes 13 ± 9° more contralateral side flexion at FFC than the upper. This is a mechanism hypothesis, not a demonstrated risk factor — the injured-vs-uninjured test comes in the 2021 paper.

Cue 2 — Distrust single-segment “lumbar angle” numbers.

• The cue: If an app, a coach, or a paper quotes you one “lumbar side flexion” or “trunk lateral flexion” figure, treat it as an average that hides a 13° difference between two halves of the same spine.
• Camera view + frame: Applies to any analysis you read or run.
• Why it matters: A bowler whose total lumbar side flexion looks normal could still be loading the lower segment heavily. This paper is the reason the later work in this cluster keeps splitting the spine.

No direct “do this instead” cue is supported by this paper. Any advice to reduce a specific angle would be invented.

Caveats and limits

• Sample: 20 elite male bowlers, mean age 19.3. Nothing here applies to women, to juniors, or to club bowlers without further evidence.
• One trial per bowler (the fastest). Technique varies delivery-to-delivery; a later paper in this cluster cites ICC = 0.98 repeatability to justify this, but it remains one delivery.
• Descriptive only. No injury data at all. This paper cannot tell you what is risky — only what moves where.
• Skin-mounted markers over lumbar spinous processes are an approximation of vertebral motion. Soft-tissue movement over the low back is real and the paper does not report a validation of segment angles against imaging.
• Conference abstract. No tables, no per-instant absolute angles, no p-values per variable — only “P < 0.05, r > 0.50” as a blanket statement. The absolute joint angles are not reported in the source I could access; only between-segment differences.
• No static trial issue disclosed here, though the closely-related 2020 paper notes no static trial was used “to preserve the natural posture of the lumbar spine” — meaning these are angles relative to the segment below, not to a neutral standing reference.

Relationship to other Felton work

• Directly re-presented as the 2023 item in this cluster (7th World Congress of Science and Medicine in Cricket) — the two abstracts are word-for-word identical. See 2023 Alway — Upper vs Lower Lumbar Spine Kinematics (World Congress re-presentation).
• Sets up the 2020 ISBS paper (2020 Alway — Does Lumbar Spine Kinematics Contribute to Lumbar Bone Stress Injury?), which does exactly what this abstract’s final sentence asks: compares upper and lower lumbar kinematics between injured and uninjured bowlers. That study found no significant differences — which qualifies the optimism here.
• Methodologically underpins the 2021 MSSE paper (2021 Alway — Cricket Fast Bowling Technique and Lumbar Bone Stress Injury), whose central conclusion — that the lumbopelvic junction, not the thoracolumbar junction, is where injury-relevant motion happens — is the same “look lower down the spine” logic applied one level further down.

CONTRADICTION: This abstract implies that separating upper from lower lumbar segments will explain lumbar stress fracture aetiology (“which may affect the aetiology of lumbar stress fractures”). The follow-up by the same authors (Alway et al., 2020, ISBS) found no statistically significant difference in any upper or lower lumbar joint angle between injured and uninjured bowlers. The two-segment lumbar model was a genuine methodological improvement, but splitting the lumbar spine did not by itself reveal the injury mechanism. The answer, when it came in 2021, was one joint lower — at the lumbopelvic junction.