{
  "resourceType": "ActivityDefinition",
  "id": "leg-extension",
  "url": "https://bodyiq.dev/fhir/ActivityDefinition/leg-extension",
  "version": "1",
  "name": "LegExtension",
  "title": "Leg Extension",
  "status": "draft",
  "experimental": true,
  "description": "An open-kinetic-chain, single-joint knee extension performed on a leg extension machine. Sit tall with your back and hips against the pads, hips flexed to roughly 90 degrees, and hook the shins behind the padded roller so the pad rests just above the ankles. Align the machine's axis of rotation with the lateral knee joint line. Fasten the lap belt if available and hold the seat handles. Extend both knees smoothly until they are nearly straight (stopping short of a hard, hyperextended lockout), pause briefly with the quadriceps contracted, then lower under control back to the start. Keep the movement slow and deliberate rather than swinging the weight up.",
  "useContext": [
    {
      "code": {
        "system": "http://terminology.hl7.org/CodeSystem/usage-context-type",
        "code": "user"
      },
      "valueCodeableConcept": {
        "text": "difficulty: beginner"
      }
    }
  ],
  "topic": [
    {
      "coding": [
        {
          "system": "https://bodyiq.dev/fhir/CodeSystem/exercise",
          "code": "leg-extension",
          "display": "Leg Extension"
        }
      ]
    }
  ],
  "bodySite": [
    {
      "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": "General resistance-training guidelines apply, as no leg-extension-specific dosing is well established: for hypertrophy roughly 3-4 sets of 8-12 reps; for muscular endurance/early rehab 2-3 sets of 12-20 reps with lighter load; train the target 2-3 times per week with about 48 hours between sessions, progressing load as tolerated. In patellofemoral rehab, limiting range to the terminal ~45-0 degrees is commonly used to reduce joint stress."
    }
  ],
  "usage": "Evidence: moderate. Surface EMG studies of open-chain knee extension consistently show high, well-balanced activation across the quadriceps heads. Contrary to older claims, the vastus medialis (VMO) cannot be selectively isolated from the rest of the quadriceps; VMO-to-vastus-lateralis activation ratios generally stay close to 1:1 across the range, though vastus medialis activity tends to be relatively higher in the terminal (near-full-extension) portion. Rectus femoris activation is somewhat blunted in the seated, hip-flexed position because the muscle is on relative slack. Compared with closed-chain movements like the squat, the open-chain leg extension isolates the quadriceps with minimal hamstring co-contraction. Note that peak patellofemoral joint compression occurs in the more flexed portion of the range while anterior tibiofemoral shear is greatest near terminal extension, which informs range selection in patellofemoral or ACL rehab.",
  "note": [
    {
      "text": "Sit tall with your back flat against the pad and line the knee joint up with the machine's pivot; the roller should rest just above the ankles, not on the shin bone."
    },
    {
      "text": "Straighten the knees smoothly and squeeze the thighs at the top, stopping just short of a forced hyperextended lockout."
    },
    {
      "text": "Lower the weight slowly (about 2-3 seconds) and stay in control instead of letting the plates drop or swinging your torso."
    },
    {
      "text": "Exhale as you extend the knees and inhale as you lower; avoid gripping the seat so hard that you brace unnecessarily."
    }
  ],
  "extension": [
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Quadriceps Femoris"
        },
        {
          "url": "role",
          "valueCode": "primary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "21989003"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Vastus Lateralis"
        },
        {
          "url": "role",
          "valueCode": "primary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "1403006"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Vastus Medialis"
        },
        {
          "url": "role",
          "valueCode": "primary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "3478008"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Vastus Intermedius"
        },
        {
          "url": "role",
          "valueCode": "primary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "57733007"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Rectus Femoris"
        },
        {
          "url": "role",
          "valueCode": "secondary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "72226001"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Hamstrings (Group)"
        },
        {
          "url": "role",
          "valueCode": "lengthening"
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Biceps Femoris — Long Head"
        },
        {
          "url": "role",
          "valueCode": "lengthening"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "55190004"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Semitendinosus"
        },
        {
          "url": "role",
          "valueCode": "lengthening"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "50340007"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Gastrocnemius"
        },
        {
          "url": "role",
          "valueCode": "lengthening"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "35616000"
          }
        }
      ]
    }
  ]
}