{
  "resourceType": "ActivityDefinition",
  "id": "sit-up",
  "url": "https://bodyiq.dev/fhir/ActivityDefinition/sit-up",
  "version": "1",
  "name": "SitUp",
  "title": "Sit-Up",
  "status": "draft",
  "experimental": true,
  "description": "Lie supine with knees bent to about 90 degrees and feet flat on the floor, arms crossed over the chest or hands lightly behind the ears. Curl the trunk by flexing the spine segmentally, then continue rising through hip flexion until the torso is upright, and lower back down with control to the start position.",
  "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": "sit-up",
          "display": "Sit-Up"
        }
      ]
    }
  ],
  "bodySite": [
    {
      "coding": [
        {
          "system": "https://bodyiq.dev/fhir/CodeSystem/exercise",
          "code": "lumbar-spine",
          "display": "Lumbar Spine"
        },
        {
          "system": "http://snomed.info/sct",
          "code": "23526008",
          "display": "Structure of lumbar intervertebral disc"
        }
      ],
      "text": "Lumbar Spine"
    },
    {
      "coding": [
        {
          "system": "https://bodyiq.dev/fhir/CodeSystem/exercise",
          "code": "thoracic-spine",
          "display": "Thoracic Spine"
        },
        {
          "system": "http://snomed.info/sct",
          "code": "5261000",
          "display": "Structure of thoracic intervertebral disc"
        }
      ],
      "text": "Thoracic Spine"
    },
    {
      "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": "cervical-spine",
          "display": "Cervical Spine"
        },
        {
          "system": "http://snomed.info/sct",
          "code": "68818006",
          "display": "Structure of cervical intervertebral disc"
        }
      ],
      "text": "Cervical Spine"
    }
  ],
  "kind": "ServiceRequest",
  "usage": "Evidence: moderate. EMG studies consistently show the sit-up is a two-phase movement: rectus abdominis and the obliques dominate the initial trunk-curl (roughly the first third of range), after which the hip flexors — psoas major, iliacus, and rectus femoris — become the primary torque producers as the trunk rises off the floor. Indwelling-EMG work has demonstrated substantial psoas activation during both bent-knee and straight-leg sit-ups, with bent knees not eliminating hip-flexor involvement as once believed. Anchoring the feet further increases hip-flexor and rectus femoris recruitment. Spine biomechanics research (notably McGill's laboratory) has measured lumbar compression during repeated full sit-ups at levels approaching occupational action limits (on the order of 3000+ N), which is the basis for preferring curl-up variations in low-back pain populations. Trunk-flexor activation in a partial curl-up is comparable to the full sit-up with markedly lower lumbar load, which is why the crunch and McGill curl-up serve as regressions rather than fundamentally different exercises.",
  "note": [
    {
      "text": "Peel your spine off the floor one segment at a time rather than jerking up in one piece."
    },
    {
      "text": "Imagine curling your ribs down toward your pelvis as you rise."
    },
    {
      "text": "Keep your chin gently tucked, as if holding a small orange under it, so your neck does not lead the movement."
    },
    {
      "text": "Lower down as slowly as you came up, letting the floor meet your back one segment at a time."
    }
  ],
  "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": "External Oblique"
        },
        {
          "url": "role",
          "valueCode": "secondary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "1179024003"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Internal Oblique"
        },
        {
          "url": "role",
          "valueCode": "secondary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "1179024003"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Rectus Femoris"
        },
        {
          "url": "role",
          "valueCode": "synergist"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "72226001"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Sternocleidomastoid"
        },
        {
          "url": "role",
          "valueCode": "synergist"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "22823000"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Transversus Abdominis"
        },
        {
          "url": "role",
          "valueCode": "stabilizer"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "86493009"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Tensor Fasciae Latae"
        },
        {
          "url": "role",
          "valueCode": "synergist"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "28190000"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Erector Spinae Group"
        },
        {
          "url": "role",
          "valueCode": "lengthening"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "44947003"
          }
        }
      ]
    }
  ]
}