Get HRV RMSSD

Get HRV RMSSD

Daily RMSSD index (Root Mean Square of Successive Differences, a heart rate variability marker), aggregated from all sources: connected wearables (Suunto, Oura, Whoop, Zepp…), the Nolio in-app HRV measurement, or manual entry.

For the full beat-to-beat detail of an in-app measurement (raw RR intervals, spectral indices), use Get HRV Measures instead.

Endpoint:

• /get/hrv/rmssd/
• HTTP Method: GET

Parameters

Parameter	Required	Type	Description
from	no	string	Start date (inclusive), format YYYY-MM-DD
to	no	string	End date (inclusive), format YYYY-MM-DD
limit	no	int	Maximum number of values returned (default 15, max 366)
source	no	string	Filter on a single source. See source values below
athlete_id	no	int	For coaches: retrieve data of a managed athlete. You can retrieve the ids with the Get Athletes route

If neither from nor to is given, the most recent values are returned (bounded by limit). Results are ordered most recent first.

source values

The source field (in the response, and the source query filter) is the connector that provided the value, or null for a manually entered value. Common values: Suunto, Oura, whoop, zepp, nolio_hrv (Nolio in-app measurement). Values are case-sensitive.

Examples

Last 15 RMSSD values, all sources:
https://www.nolio.io/api/get/hrv/rmssd/

RMSSD over a date range:
https://www.nolio.io/api/get/hrv/rmssd/?from=2025-01-01&to=2025-12-31

Only Oura-sourced RMSSD:
https://www.nolio.io/api/get/hrv/rmssd/?source=Oura

RMSSD of a managed athlete (coach access):
https://www.nolio.io/api/get/hrv/rmssd/?athlete_id=456

Returns

A JSON array of Metric objects (most recent first). Each object adds a source field:

Field	Type	Description
id	int	Metric ID
date	string	Date of the value (YYYY-MM-DD)
hour	string	Time of the value (HH:MM), or "" if not set
value	float	RMSSD value
unit	string	ms
type	string	RMSSD
source	string or null	Connector that provided the value, or null if entered manually

Example response

[
  {
    "id": 998123,
    "date": "2025-06-15",
    "hour": "07:12",
    "value": 52.3,
    "unit": "ms",
    "type": "RMSSD",
    "source": "Oura"
  },
  {
    "id": 997004,
    "date": "2025-06-14",
    "hour": "",
    "value": 48.9,
    "unit": "ms",
    "type": "RMSSD",
    "source": "nolio_hrv"
  }
]

Overlap with Get HRV Measures: a Nolio in-app HRV measurement also produces an RMSSD value here with source = nolio_hrv. The same measurement appears in full detail in Get HRV Measures. Filter on source to select or deduplicate.

Errors

• 400 - Invalid date format for from or to
• 400 - Invalid source value