{
  "resourceType": "ActivityDefinition",
  "id": "tuck-l-sit",
  "url": "https://bodyiq.dev/fhir/ActivityDefinition/tuck-l-sit",
  "version": "1",
  "name": "TuckLSit",
  "title": "Tuck L-Sit",
  "status": "draft",
  "experimental": true,
  "description": "Support hold with the knees drawn toward the chest and the feet clear of the floor, shortening the lower-limb lever so the hip flexors and abdominals hold a compact mass.",
  "useContext": [
    {
      "code": {
        "system": "http://terminology.hl7.org/CodeSystem/usage-context-type",
        "code": "user"
      },
      "valueCodeableConcept": {
        "text": "difficulty: intermediate"
      }
    }
  ],
  "topic": [
    {
      "coding": [
        {
          "system": "https://bodyiq.dev/fhir/CodeSystem/exercise",
          "code": "tuck-l-sit",
          "display": "Tuck L-Sit"
        }
      ]
    }
  ],
  "bodySite": [
    {
      "coding": [
        {
          "system": "https://bodyiq.dev/fhir/CodeSystem/exercise",
          "code": "shoulder",
          "display": "Shoulder"
        },
        {
          "system": "http://snomed.info/sct",
          "code": "264190008",
          "display": "Structure of scapulothoracic joint"
        }
      ],
      "text": "Shoulder"
    },
    {
      "coding": [
        {
          "system": "https://bodyiq.dev/fhir/CodeSystem/exercise",
          "code": "elbow",
          "display": "Elbow"
        },
        {
          "system": "http://snomed.info/sct",
          "code": "44034005",
          "display": "Structure of humeroulnar joint"
        }
      ],
      "text": "Elbow"
    },
    {
      "coding": [
        {
          "system": "https://bodyiq.dev/fhir/CodeSystem/exercise",
          "code": "hip",
          "display": "Hip"
        },
        {
          "system": "http://snomed.info/sct",
          "code": "24136001",
          "display": "Structure of hip joint"
        }
      ],
      "text": "Hip"
    },
    {
      "coding": [
        {
          "system": "https://bodyiq.dev/fhir/CodeSystem/exercise",
          "code": "knee",
          "display": "Knee"
        },
        {
          "system": "http://snomed.info/sct",
          "code": "129159008",
          "display": "Structure of femorotibial joint"
        }
      ],
      "text": "Knee"
    }
  ],
  "kind": "ServiceRequest",
  "dosage": [
    {
      "text": "3 holds × 15–30 s, 2–3×/week (consensus programming, not RCT-derived)"
    }
  ],
  "usage": "Evidence: expert-opinion.",
  "note": [
    {
      "text": "Round your lower back slightly and pull the knees up, rather than leaning back",
      "authorString": "focus:external"
    },
    {
      "text": "Shoulders stay down the whole time — if they shrug, the hold is over",
      "authorString": "focus:external"
    }
  ],
  "relatedArtifact": [
    {
      "type": "citation",
      "label": "bodyweight-progression-consensus-2026",
      "citation": "r/bodyweightfitness Recommended Routine contributors; allied coaching material. (2026). Community-consensus bodyweight progression sequences"
    },
    {
      "type": "successor",
      "label": "3 holds × 15 s with the hips clear of the floor and the knees at chest height",
      "display": "L-Sit",
      "resource": "ActivityDefinition/l-sit"
    },
    {
      "type": "predecessor",
      "label": "The feet cannot leave the floor without shrugging",
      "display": "Foot-Supported L-Sit",
      "resource": "ActivityDefinition/foot-supported-l-sit"
    }
  ],
  "extension": [
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Rectus Abdominis"
        },
        {
          "url": "role",
          "valueCode": "primary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "31243008"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Iliopsoas"
        },
        {
          "url": "role",
          "valueCode": "primary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "68455001"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Lower Trapezius"
        },
        {
          "url": "role",
          "valueCode": "secondary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "31764008"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Triceps Brachii"
        },
        {
          "url": "role",
          "valueCode": "secondary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "40284004"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "External Oblique"
        },
        {
          "url": "role",
          "valueCode": "stabilizer"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "1179024003"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Serratus Anterior"
        },
        {
          "url": "role",
          "valueCode": "stabilizer"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "18346003"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Latissimus Dorsi"
        },
        {
          "url": "role",
          "valueCode": "stabilizer"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "15665001"
          }
        }
      ]
    }
  ]
}