"hollow body position" meaning in English

{
  "forms": [
    {
      "form": "hollow body positions",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "hollow body position (plural hollow body positions)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Gymnastics",
          "orig": "en:Gymnastics",
          "parents": [
            "Sports",
            "Human activity",
            "Human behaviour",
            "Human",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A position with a posterior pelvic tilt, i.e. with the lower back held flat"
      ],
      "id": "en-hollow_body_position-en-noun-rSPD--Io",
      "links": [
        [
          "gymnastics",
          "gymnastics"
        ],
        [
          "posterior",
          "posterior"
        ],
        [
          "pelvic tilt",
          "pelvic tilt"
        ],
        [
          "lower back",
          "lower back"
        ]
      ],
      "raw_glosses": [
        "(gymnastics) A position with a posterior pelvic tilt, i.e. with the lower back held flat"
      ],
      "topics": [
        "gymnastics",
        "hobbies",
        "lifestyle",
        "sports"
      ]
    }
  ],
  "word": "hollow body position"
}

{
  "forms": [
    {
      "form": "hollow body positions",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "hollow body position (plural hollow body positions)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "en:Gymnastics"
      ],
      "glosses": [
        "A position with a posterior pelvic tilt, i.e. with the lower back held flat"
      ],
      "links": [
        [
          "gymnastics",
          "gymnastics"
        ],
        [
          "posterior",
          "posterior"
        ],
        [
          "pelvic tilt",
          "pelvic tilt"
        ],
        [
          "lower back",
          "lower back"
        ]
      ],
      "raw_glosses": [
        "(gymnastics) A position with a posterior pelvic tilt, i.e. with the lower back held flat"
      ],
      "topics": [
        "gymnastics",
        "hobbies",
        "lifestyle",
        "sports"
      ]
    }
  ],
  "word": "hollow body position"
}