diff --git a/Strand/App/AppModel.swift b/Strand/App/AppModel.swift
index 588a25d37e..e4107eea73 100644
--- a/Strand/App/AppModel.swift
+++ b/Strand/App/AppModel.swift
@@ -127,6 +127,31 @@ final class AppModel: ObservableObject {
 
         var isPaused: Bool { pausedAt != nil }
 
+        /// Adds a heart-rate sample unless this second already has one, and says whether it did.
+        ///
+        /// `captureWorkoutSample` runs from two `@Published` sinks (`heartRate` and `rr`), so a strap sends
+        /// it one call per R-R packet plus another whenever the rate itself moves, which during exercise is
+        /// most seconds: two samples with one `ts`. Effort credits each sample with the gap to the next and a
+        /// zero gap with a full second (`StrainScorer.sampleDurationsMinutes`), so every repeat counted as
+        /// another second of effort, live and in the saved workout. The stream is one reading a second.
+        ///
+        /// A refused reading still reaches `peakHr`: the sinks fire because the rate moved, so a repeat is often a
+        /// different bpm for that second, and a within-second high is part of the workout's peak. Only the last
+        /// sample is compared, so this drops a repeat of the current second, not an out-of-order arrival; the live
+        /// stream is monotonic.
+        mutating func recordSample(_ sample: HRSample) -> Bool {
+            if let last = samples.last, last.ts == sample.ts {
+                peakHr = max(peakHr, sample.bpm)
+                return false
+            }
+            samples.append(sample)
+            return true
+        }
+
+        /// The maximum heart rate the workout is saved with: the highest sample, or a higher reading a repeated
+        /// second folded into `peakHr` (`recordSample`). Nil with no samples.
+        var savedPeak: Int? { samples.map(\.bpm).max().map { max($0, peakHr) } }
+
         /// Delegates to `ActiveWorkoutClock` so this and the two card surfaces cannot drift apart again.
         func elapsed(at now: Date = Date()) -> TimeInterval {
             ActiveWorkoutClock.activeElapsed(start: start, pausedAt: pausedAt,
@@ -985,7 +1010,7 @@ final class AppModel: ObservableObject {
         }
         let avg = samples.isEmpty ? nil
             : Int((Double(samples.map(\.bpm).reduce(0, +)) / Double(samples.count)).rounded())
-        let peak = samples.map(\.bpm).max()
+        let peak = w.savedPeak
         // #983: score the SAVED workout with the wearer's measured resting HR, not the hardcoded
         // default of 60. %HRR is (bpm - resting) / (max - resting), so the default moves every zone
         // boundary — at 136 bpm with maxHR 190 it is the difference between zone 1 and zone 2. Today's
@@ -1045,7 +1070,13 @@ final class AppModel: ObservableObject {
     /// over the growing window each sample is cheap at the ~1 Hz live-HR cadence.
     private func captureWorkoutSample() {
         guard var w = activeWorkout, !w.isPaused, let hr = bpm else { return }
-        w.samples.append(HRSample(ts: Int(Date().timeIntervalSince1970), bpm: hr))
+        // A second that already has its sample moves only the peak: publish that, and skip the rescore and the
+        // snapshot (the next second's sample carries the peak into the snapshot).
+        let peakBefore = w.peakHr
+        guard w.recordSample(HRSample(ts: Int(Date().timeIntervalSince1970), bpm: hr)) else {
+            if w.peakHr != peakBefore { activeWorkout = w }
+            return
+        }
         w.peakHr = max(w.peakHr, hr)
         w.avgHr = Int((Double(w.samples.map(\.bpm).reduce(0, +)) / Double(w.samples.count)).rounded())
         w.liveStrain = StrainScorer.strain(w.samples, maxHR: Double(profile.hrMax),
diff --git a/StrandTests/WorkoutSampleOncePerSecondTests.swift b/StrandTests/WorkoutSampleOncePerSecondTests.swift
new file mode 100644
index 0000000000..92be51c84e
--- /dev/null
+++ b/StrandTests/WorkoutSampleOncePerSecondTests.swift
@@ -0,0 +1,55 @@
+import XCTest
+import StrandAnalytics
+import WhoopProtocol
+@testable import Strand
+
+/// A manual workout records one heart-rate sample a second. The live heart rate reaches it once per R-R packet and
+/// again whenever the rate moves, and Effort credits a repeated second as another second of effort.
+final class WorkoutSampleOncePerSecondTests: XCTestCase {
+
+    func testASecondThatAlreadyHasASampleTakesNoOther() {
+        var workout = AppModel.ActiveWorkout(start: Date(timeIntervalSince1970: 1_000))
+        XCTAssertTrue(workout.recordSample(HRSample(ts: 1_000, bpm: 120)))
+        XCTAssertFalse(workout.recordSample(HRSample(ts: 1_000, bpm: 121)))
+        XCTAssertTrue(workout.recordSample(HRSample(ts: 1_001, bpm: 122)))
+        XCTAssertEqual(workout.samples.map(\.ts), [1_000, 1_001])
+        XCTAssertEqual(workout.samples.map(\.bpm), [120, 122])
+    }
+
+    /// The rate moving is often why a second arrives twice, so the refused reading can be that second's high: it is
+    /// not recorded, but it is the workout's peak, live and saved.
+    func testARepeatedSecondStillReachesThePeak() {
+        var workout = AppModel.ActiveWorkout(start: Date(timeIntervalSince1970: 1_000))
+        XCTAssertNil(workout.savedPeak)
+        _ = workout.recordSample(HRSample(ts: 1_000, bpm: 120))
+        workout.peakHr = 120   // what captureWorkoutSample does after an accepted sample
+        XCTAssertFalse(workout.recordSample(HRSample(ts: 1_000, bpm: 131)))
+        XCTAssertEqual(workout.samples.map(\.bpm), [120])
+        XCTAssertEqual(workout.peakHr, 131)
+        XCTAssertEqual(workout.savedPeak, 131)
+        XCTAssertFalse(workout.recordSample(HRSample(ts: 1_000, bpm: 125)))   // a lower repeat moves nothing
+        XCTAssertEqual(workout.peakHr, 131)
+    }
+
+    /// Twenty minutes climbing from 100 to 160 bpm, each second arriving twice (the R-R packet, then the rate
+    /// moving) as it does during exercise. Recorded through `recordSample`, the workout's Effort is the Effort of
+    /// the plain once-a-second stream; the repeats, kept, scored higher.
+    func testRepeatedSecondsNoLongerAddEffort() {
+        let seconds = 20 * 60
+        let clean = (0..<seconds).map { HRSample(ts: 5_000 + $0, bpm: 100 + $0 * 60 / seconds) }
+        var workout = AppModel.ActiveWorkout(start: Date(timeIntervalSince1970: 5_000))
+        var everyArrival: [HRSample] = []
+        for sample in clean {
+            for _ in 0..<2 {
+                _ = workout.recordSample(sample)
+                everyArrival.append(sample)
+            }
+        }
+        func effort(_ samples: [HRSample]) -> Double {
+            StrainScorer.strain(samples, maxHR: 190, restingHR: 60) ?? 0
+        }
+        XCTAssertEqual(workout.samples.map(\.ts), clean.map(\.ts))
+        XCTAssertEqual(effort(workout.samples), effort(clean))
+        XCTAssertGreaterThan(effort(everyArrival), effort(clean))
+    }
+}
diff --git a/android/app/src/main/java/com/noop/ui/AppViewModel.kt b/android/app/src/main/java/com/noop/ui/AppViewModel.kt
index d66d6d0f4e..ef3792174f 100644
--- a/android/app/src/main/java/com/noop/ui/AppViewModel.kt
+++ b/android/app/src/main/java/com/noop/ui/AppViewModel.kt
@@ -1732,7 +1732,8 @@ class AppViewModel(app: Application) : AndroidViewModel(app) {
         val pausedMs = w.pausedDurationMs + (w.pausedAtMs?.let { endMs - it } ?: 0L)
         val activeDurationMs = (endMs - w.startMs - pausedMs).coerceAtLeast(0L)
         val avg = if (samples.isNotEmpty()) samples.sumOf { it.bpm } / samples.size else null
-        val peak = if (samples.isNotEmpty()) samples.maxOf { it.bpm } else null
+        // `w.peakHr` can exceed every sample: a repeated second's higher reading is folded into it, not recorded.
+        val peak = if (samples.isNotEmpty()) maxOf(samples.maxOf { it.bpm }, w.peakHr) else null
         // #983: score the SAVED workout with the wearer's measured resting HR, not the hardcoded
         // default of 60. %HRR is (bpm - resting) / (max - resting), so the default moves every zone
         // boundary — at 136 bpm with maxHR 190 it is the difference between zone 1 and zone 2. Today's
@@ -1801,12 +1802,24 @@ class AppViewModel(app: Application) : AndroidViewModel(app) {
         @Suppress("UNNECESSARY_SAFE_CALL")
         val w = _activeWorkout?.value ?: return
         if (w.pausedAtMs != null) return
-        val s = w.samples + HrSample(deviceId = deviceId, ts = System.currentTimeMillis() / 1000, bpm = bpm)
+        // One sample a second. This runs on every LiveState emission that carries a heart rate — any field
+        // changing, not only the rate — so a second often arrives more than once with one `ts`, and Effort
+        // credits a zero gap with a full second (`StrainScorer.sampleDurationsMinutes`): each repeat counted
+        // as another second of effort, live and in the saved workout. A refused reading still reaches the peak: the
+        // rate moving is often why this ran, so it can be a within-second high; only the peak is published for it,
+        // with no rescore and no snapshot. Twin of iOS `ActiveWorkout.recordSample`.
+        val ts = System.currentTimeMillis() / 1000
+        if (w.samples.lastOrNull()?.ts == ts) {
+            if (bpm > w.peakHr) _activeWorkout.value = w.copy(peakHr = bpm)
+            return
+        }
+        val s = w.samples + HrSample(deviceId = deviceId, ts = ts, bpm = bpm)
         val strain = StrainScorer.strain(
             s, maxHR = profileStore.hrMax.toDouble(),
             method = NoopPrefs.effortMethod(appContext), sex = profileStore.sex) ?: 0.0
         val updated = w.copy(
-            samples = s, avgHr = s.sumOf { it.bpm } / s.size, peakHr = s.maxOf { it.bpm }, liveStrain = strain,
+            // Grown by comparison, not recomputed from `s`, so a peak folded in from a repeated second is kept.
+            samples = s, avgHr = s.sumOf { it.bpm } / s.size, peakHr = maxOf(w.peakHr, bpm), liveStrain = strain,
         )
         _activeWorkout.value = updated
         // Re-snapshot the durable non-GPS session so a process kill keeps the latest accumulated HR (#529).