What is the best app to analyse Garmin data?

Intervals.icu, and it is free. It pulls from Garmin automatically, models load with a visible formula, and gives you power and pace curves Connect does not. Runalyze is the other strong free option, with particularly good running-specific modelling.

Can I replace Garmin Connect entirely?

Not really, and you would not want to. It is the sync path off the watch and the store for the raw files. Every alternative on this list reads from Connect rather than replacing it, so the useful question is what to add on top.

Why does Body Battery disagree with how I feel?

Because it is a proprietary composite of HRV, stress, sleep and activity with undisclosed weights, and because it reads fatigue through the autonomic nervous system. A heavy lifting session produces mechanical and neural fatigue that barely moves those inputs, so a hard strength day can leave Body Battery high while your actual capacity is down.

Does Garmin Connect track strength training properly?

It logs a strength activity, and on some watches it will count sets and guess reps. What it does not do is track load per set, proximity to failure, or estimated one-rep max over time, and none of the lifting enters its load or readiness modelling in a meaningful way. It is a record, not a model.

Is Garmin Training Readiness accurate?

It is a reasonable composite of real inputs and it is undocumented, which means you cannot tell when it is wrong. It also weights sleep and HRV heavily and lifting barely at all, so for a hybrid athlete it systematically overestimates readiness after heavy strength work.

Garmin Connect Alternatives Worth Adding

What Connect does well

It holds the raw data, it is free with the hardware, its sleep and HRV measurement is respectable, and its endurance load modelling — Training Load, Acute Load, Training Status — covers most of what a self-coached athlete needs.

Where it frustrates people

Nothing shows its arithmetic. Body Battery, Training Readiness, Training Status and Endurance Score are proprietary composites with undisclosed weights. When one disagrees with how you feel, there is no input to inspect and no way to learn whether the number or your perception was wrong. Over years, that is the difference between a metric you trust and one you ignore.

Strength is a recording, not a model. Newer watches count sets and estimate reps. Connect does not track load per set, RIR, or e1RM trend, and lifting contributes almost nothing to Training Load. So a week of heavy squatting reads as a light week. Why heart-rate-derived load misses resistance training.

Readiness weights the wrong things for a hybrid athlete. Sleep and HRV dominate; mechanical fatigue is invisible. The systematic error is in the dangerous direction — it says go when you should not.

The interface. Deep, inconsistent, and slow to find anything twice.

What to add

Intervals.icu — free, and better modelling than Connect

Syncs from Garmin automatically. Gives you a full Performance Management Chart with CTL, ATL and TSB, power and pace curves, HRV trends, and custom fields — and it shows you the formula. Strictly additive: it changes nothing about how you record. Where it stops for hybrid athletes.

Runalyze — free, running-specific depth

Marathon shape, VO2max estimation, effort scoring and race prediction, with a stronger running focus than Intervals.icu's cycling heritage. Also free, also additive.

Connect's feed is technically present and socially empty. If community, segments and clubs are the missing piece, Strava is what provides it, and its analysis is not the reason to add it. What Strava does and does not model.

A real strength log

This is the gap none of the above fills. Connect records that you lifted; it does not hold the numbers that make lifting progressable — load per set, reps in reserve, e1RM over weeks. For that you need a proper lifting log, which then leaves you with two systems and no shared view. Why that split costs you the cross-discipline decisions.

The comparison

	Garmin Connect	Intervals.icu	Runalyze	Strava	Base
Cost	With device	Free	Free	Free / Premium	Beta
Reads Garmin data	Native	Automatic	Automatic	Automatic	Via your health source
Endurance load model	Proprietary	CTL/ATL/TSB, visible	Running-specific	Shallow	Ramp rate on minutes
Shows its arithmetic	No	Yes	Mostly	No	Every derived number
Social layer	Empty	No	No	Best	No
Strength load per set	No	No	No	No	Yes, with RIR
Lifting affects readiness	Barely	No	No	No	Yes
Nutrition	Basic	No	No	No	Adaptive, same ledger
Baseline compared against	Proprietary	Yours	Yours	N/A	Your own 30 days

The honest recommendation

Keep Connect and add Intervals.icu. Ten minutes to set up, free, and it gives you a load model you can argue with. This is the single best change available to most Garmin owners.

Add Runalyze instead if you are a runner rather than a cyclist and want race prediction and shape modelling.

Add Strava if you want people, not data.

Add a real strength system if you lift seriously. Connect will keep telling you a heavy squat week was restful, and the number that would correct it — weekly hard sets per muscle group against your endurance load — does not exist anywhere in the Garmin ecosystem. What both halves on one ledger looks like.

Two free things worth doing today: derive your own threshold pace zones rather than trusting the watch's, and count your weekly hard sets. Most Garmin owners' prescribed easy pace is faster than their actual easy pace, and that is the most common way concurrent training quietly fails.