{
  "resourceType": "ActivityDefinition",
  "id": "posterior-chain-strengthening",
  "url": "https://bodyiq.dev/fhir/ActivityDefinition/posterior-chain-strengthening",
  "version": "1",
  "name": "PosteriorChainStrengthening",
  "title": "Hamstring and Calf Strengthening",
  "status": "draft",
  "experimental": true,
  "description": "Posterior chain strengthening to balance knee joint forces and improve functional capacity. Includes prone hamstring curls, seated heel raises, and nordic hamstring eccentric exercises. Supports weight-bearing activities and stair negotiation.",
  "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": "posterior-chain-strengthening",
          "display": "Hamstring and Calf Strengthening"
        }
      ]
    }
  ],
  "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"
    },
    {
      "coding": [
        {
          "system": "https://bodyiq.dev/fhir/CodeSystem/exercise",
          "code": "ankle",
          "display": "Ankle"
        },
        {
          "system": "http://snomed.info/sct",
          "code": "70258002",
          "display": "Structure of ankle joint"
        }
      ],
      "text": "Ankle"
    }
  ],
  "kind": "ServiceRequest",
  "dosage": [
    {
      "text": "3×10-12 reps; eccentric emphasis for tendinopathy (3-4 second lowering)"
    }
  ],
  "usage": "Evidence: moderate. Nordic hamstring exercise: highest hamstring activation among eccentric exercises; semitendinosus significantly higher [Sahinis 2025]",
  "note": [
    {
      "text": "Long, neutral spine — posterior chain shortens then lengthens",
      "authorString": "focus:internal"
    },
    {
      "text": "Pull the heel toward the back pocket",
      "authorString": "focus:external"
    },
    {
      "text": "Lower over three seconds against gravity",
      "authorString": "focus:external"
    },
    {
      "text": "Posterior chain works like a fishing line reeling in",
      "authorString": "focus:imagery"
    }
  ],
  "relatedArtifact": [
    {
      "type": "citation",
      "label": "kisner-therapeutic-2017",
      "citation": "Kisner C, Colby LA, Borstad J. (2017). Therapeutic Exercise: Foundations and Techniques"
    },
    {
      "type": "citation",
      "label": "acsm-guidelines-2021",
      "citation": "American College of Sports Medicine. (2021). ACSM's Guidelines for Exercise Testing and Prescription",
      "document": {
        "url": "https://doi.org/10.4135/9781412994149.n165"
      }
    },
    {
      "type": "citation",
      "label": "va-hip-knee-oa-2020",
      "citation": "Matthew Bair MD MS, John Cody MD, Jess Edison MD, et al.. (2020). The Non-Surgical Management of Hip & Knee Osteoarthritis (OA) (2020)",
      "document": {
        "url": "https://doi.org/10.1016/j.ijotn.2020.100840"
      }
    },
    {
      "type": "citation",
      "label": "zeng-exercise-knee-oa-2022",
      "citation": "Zeng CY, Zhang ZR, Tang ZM, Hua FZ. (2022). Benefits and Mechanisms of Exercise Training for Knee Osteoarthritis",
      "document": {
        "url": "https://doi.org/10.3390/ijms232314953"
      }
    },
    {
      "type": "successor",
      "label": "Advance to eccentric Nordic once prone/seated hamstring curls are tolerated pain-free; Nordic is listed as posterior-chain-strengthening's progression.",
      "display": "Nordic Hamstring Curl",
      "resource": "ActivityDefinition/nordic-hamstring-curl"
    },
    {
      "type": "predecessor",
      "label": "Build calf endurance with double-leg heel raises before combined posterior-chain work.",
      "display": "Heel Raise (Calf Raise)",
      "resource": "ActivityDefinition/heel-raise"
    }
  ],
  "extension": [
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Hamstrings (Group)"
        },
        {
          "url": "role",
          "valueCode": "primary"
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Gastrocnemius"
        },
        {
          "url": "role",
          "valueCode": "primary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "35616000"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Soleus"
        },
        {
          "url": "role",
          "valueCode": "primary"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "78376008"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Quadriceps Femoris"
        },
        {
          "url": "role",
          "valueCode": "lengthening"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "21989003"
          }
        }
      ]
    },
    {
      "url": "https://bodyiq.dev/fhir/StructureDefinition/muscle-involvement",
      "extension": [
        {
          "url": "muscle",
          "valueString": "Tibialis Anterior"
        },
        {
          "url": "role",
          "valueCode": "lengthening"
        },
        {
          "url": "coding",
          "valueCoding": {
            "system": "http://snomed.info/sct",
            "code": "73508007"
          }
        }
      ]
    }
  ]
}