diff --git a/src/AllPlot.cpp b/src/AllPlot.cpp
index 20153f28c..f46a221ae 100644
--- a/src/AllPlot.cpp
+++ b/src/AllPlot.cpp
@@ -3480,7 +3480,7 @@ AllPlot::setDataFromPlot(AllPlot *plot)
         if (scope == RideFile::wprime) sd->setFactor(0.001f); // Kj
         if (scope == RideFile::thb || scope == RideFile::smo2 
             || scope == RideFile::o2hb || scope == RideFile::hhb) // Hb
-            sd->setDecimals(1);
+            sd->setDecimals(2);
 
         setAxisScaleDraw(QwtPlot::yLeft, sd);
 
diff --git a/src/HistogramWindow.cpp b/src/HistogramWindow.cpp
index 970fc8c8d..7603bab0b 100644
--- a/src/HistogramWindow.cpp
+++ b/src/HistogramWindow.cpp
@@ -835,7 +835,8 @@ void HistogramWindow::addSeries()
                << RideFile::cad
                << RideFile::nm
                << RideFile::aPower
-               << RideFile::gear;
+               << RideFile::gear
+               << RideFile::smo2;
 
     foreach (RideFile::SeriesType x, seriesList) 
         seriesCombo->addItem(RideFile::seriesName(x), static_cast<int>(x));
diff --git a/src/PowerHist.cpp b/src/PowerHist.cpp
index 32ce67d3b..3516e8d22 100644
--- a/src/PowerHist.cpp
+++ b/src/PowerHist.cpp
@@ -161,6 +161,10 @@ PowerHist::configChanged()
             pen.setColor(GColor(CCADENCE).darker(200));
             brush_color = GColor(CCADENCE);
             break;
+        case RideFile::smo2:
+            pen.setColor(GColor(CSMO2).darker(200));
+            brush_color = GColor(CSMO2);
+            break;
         case RideFile::gear:
             pen.setColor(GColor(CGEAR).darker(200));
             brush_color = GColor(CGEAR);
@@ -478,6 +482,11 @@ PowerHist::recalcCompare()
 
             }
 
+        } else if (series == RideFile::smo2) {
+
+            array = &cid.smo2Array;
+            arrayLength = cid.smo2Array.size();
+
         } else if (series == RideFile::gear) {
 
             array = &cid.gearArray;
@@ -1053,6 +1062,11 @@ PowerHist::binData(HistData &standard, QVector<double>&x, // x-axis for data
             selectedArray = &standard.paceZoneSelectedArray;
         }
 
+    } else if (series == RideFile::smo2) {
+        array = &standard.smo2Array;
+        arrayLength = standard.smo2Array.size();
+        selectedArray = &standard.smo2SelectedArray;
+
     } else if (series == RideFile::gear) {
         array = &standard.gearArray;
         arrayLength = standard.gearArray.size();
@@ -1255,6 +1269,7 @@ PowerHist::setData(RideFileCache *cache)
     standard.paceZoneArray.resize(10);
     standard.paceCPZoneArray.resize(3);
     standard.gearArray.resize(0);
+    standard.smo2Array.resize(0);
     standard.cadArray.resize(0);
 
     // we do not use the selected array since it is
@@ -1269,6 +1284,7 @@ PowerHist::setData(RideFileCache *cache)
     standard.hrZoneSelectedArray.resize(0);
     standard.kphSelectedArray.resize(0);
     standard.gearSelectedArray.resize(0);
+    standard.smo2SelectedArray.resize(0);
     standard.cadSelectedArray.resize(0);
 
     longFromDouble(standard.wattsArray, cache->distributionArray(RideFile::watts));
@@ -1278,6 +1294,7 @@ PowerHist::setData(RideFileCache *cache)
     longFromDouble(standard.nmArray, cache->distributionArray(RideFile::nm));
     longFromDouble(standard.cadArray, cache->distributionArray(RideFile::cad));
     longFromDouble(standard.gearArray, cache->distributionArray(RideFile::gear));
+    longFromDouble(standard.smo2Array, cache->distributionArray(RideFile::smo2));
     longFromDouble(standard.kphArray, cache->distributionArray(RideFile::kph));
 
     if (!context->athlete->useMetricUnits) {
@@ -1397,6 +1414,7 @@ PowerHist::setDataFromCompare()
         add.paceZoneArray.resize(10);
         add.paceCPZoneArray.resize(3);
         add.gearArray.resize(0);
+        add.smo2Array.resize(0);
         add.cadArray.resize(0);
 
         longFromDouble(add.wattsArray, s->distributionArray(RideFile::watts));
@@ -1405,6 +1423,7 @@ PowerHist::setDataFromCompare()
         longFromDouble(add.hrArray, s->distributionArray(RideFile::hr));
         longFromDouble(add.nmArray, s->distributionArray(RideFile::nm));
         longFromDouble(add.gearArray, s->distributionArray(RideFile::gear));
+        longFromDouble(add.smo2Array, s->distributionArray(RideFile::smo2));
         longFromDouble(add.cadArray, s->distributionArray(RideFile::cad));
         longFromDouble(add.kphArray, s->distributionArray(RideFile::kph));
 
@@ -1746,6 +1765,7 @@ PowerHist::setData(RideItem *_rideItem, bool force)
                    (series == RideFile::nm && ride->areDataPresent()->nm) ||
                    (series == RideFile::kph && ride->areDataPresent()->kph) ||
                    (series == RideFile::gear && ride->areDataPresent()->gear) ||
+                   (series == RideFile::smo2 && ride->areDataPresent()->smo2) ||
                    (series == RideFile::cad && ride->areDataPresent()->cad) ||
                    (series == RideFile::aPower && ride->areDataPresent()->apower) ||
                    (series == RideFile::hr && ride->areDataPresent()->hr);
@@ -1781,6 +1801,7 @@ PowerHist::setArraysFromRide(RideFile *ride, HistData &standard, const Zones *zo
     static const double kphDelta   = 0.1;
     static const double cadDelta   = 1.0;
     static const double gearDelta  = 0.01; //RideFileCache creates POW(10) * decimals section
+    static const double smo2Delta  = 1;
     static const int maxSize = 4096;
 
     // recording interval in minutes
@@ -1799,6 +1820,7 @@ PowerHist::setArraysFromRide(RideFile *ride, HistData &standard, const Zones *zo
     standard.paceZoneArray.resize(0);
     standard.paceCPZoneArray.resize(0);
     standard.gearArray.resize(0);
+    standard.smo2Array.resize(0);
     standard.cadArray.resize(0);
 
     standard.wattsSelectedArray.resize(0);
@@ -1810,6 +1832,7 @@ PowerHist::setArraysFromRide(RideFile *ride, HistData &standard, const Zones *zo
     standard.hrZoneSelectedArray.resize(0);
     standard.kphSelectedArray.resize(0);
     standard.gearSelectedArray.resize(0);
+    standard.smo2SelectedArray.resize(0);
     standard.cadSelectedArray.resize(0);
 
     // unit conversion factor for imperial units for selected parameters
@@ -2020,6 +2043,19 @@ PowerHist::setArraysFromRide(RideFile *ride, HistData &standard, const Zones *zo
             }
         }
 
+        int smo2Index = int(floor(p1->smo2 / smo2Delta));
+        if (smo2Index >= 0 && smo2Index < maxSize) {
+            if (smo2Index >= standard.smo2Array.size())
+                standard.smo2Array.resize(smo2Index + 1);
+            standard.smo2Array[smo2Index]++;
+
+            if (selected) {
+                if (smo2Index >= standard.smo2SelectedArray.size())
+                    standard.smo2SelectedArray.resize(smo2Index + 1);
+                standard.smo2SelectedArray[smo2Index]++;
+            }
+        }
+
         int gearIndex = int(floor(p1->gear / gearDelta));
         if (gearIndex >= 0 && gearIndex < maxSize) {
             if (gearIndex >= standard.gearArray.size())
@@ -2153,6 +2189,10 @@ PowerHist::setParameterAxisTitle()
             axislabel = tr("Gear Ratio");
             break;
 
+        case RideFile::smo2:
+            axislabel = tr("SmO2");
+            break;
+
         default:
             axislabel = QString(tr("Unknown data series"));
             break;
diff --git a/src/PowerHist.h b/src/PowerHist.h
index 11ed38cd5..917e47f27 100644
--- a/src/PowerHist.h
+++ b/src/PowerHist.h
@@ -100,7 +100,7 @@ class HistData // each curve needs a lot of data (!? this may need refactoring,
                               wattsCPZoneArray, wattsKgArray, nmArray,
                               hrArray, hrZoneArray, hrCPZoneArray,
                               kphArray, paceZoneArray, paceCPZoneArray,
-                              cadArray, gearArray, metricArray;
+                              cadArray, gearArray, smo2Array, metricArray;
 
         // storage for data counts in interval selected
         QVector<unsigned int> aPowerSelectedArray, wattsSelectedArray,
@@ -108,7 +108,7 @@ class HistData // each curve needs a lot of data (!? this may need refactoring,
                               wattsKgSelectedArray, nmSelectedArray,
                               hrSelectedArray, hrZoneSelectedArray, hrCPZoneSelectedArray,
                               kphSelectedArray, paceZoneSelectedArray, paceCPZoneSelectedArray,
-                              cadSelectedArray, gearSelectedArray;
+                              cadSelectedArray, smo2SelectedArray, gearSelectedArray;
 };
 
 class PowerHist : public QwtPlot
diff --git a/src/RideFileCache.cpp b/src/RideFileCache.cpp
index b184eec62..ca2444ce9 100644
--- a/src/RideFileCache.cpp
+++ b/src/RideFileCache.cpp
@@ -66,6 +66,7 @@ RideFileCache::RideFileCache(Context *context, QString fileName, RideFile *passe
     npDistribution.resize(0);
     wattsKgDistribution.resize(0);
     aPowerDistribution.resize(0);
+    smo2Distribution.resize(0);
 
     // time in zone are fixed to 10 zone max
     wattsTimeInZone.resize(10);
@@ -205,6 +206,7 @@ static long offsetForTiz(RideFileCacheHeader head, RideFile::SeriesType series)
     offset += head.npDistCount * sizeof(float);
     offset += head.wattsKgDistCount * sizeof(float);
     offset += head.aPowerDistCount * sizeof(float);
+    offset += head.smo2DistCount * sizeof(float);
 
     // tiz ist currently just for RideFile:watts, RideFile:hr and RideFile:kph series.
     // watts is first - so move on with offset only for 'hr' and 'kph'
@@ -376,6 +378,7 @@ RideFileCache::RideFileCache(RideFile *ride) :
     npDistribution.resize(0);
     wattsKgDistribution.resize(0);
     aPowerDistribution.resize(0);
+    smo2Distribution.resize(0);
 
     // time in zone are fixed to 10 zone max
     wattsTimeInZone.resize(10);
@@ -418,6 +421,7 @@ RideFileCache::RideFileCache(RideFile *ride) :
     doubleArrayForDistribution(npDistributionDouble, npDistribution);
     doubleArrayForDistribution(wattsKgDistributionDouble, wattsKgDistribution);
     doubleArrayForDistribution(aPowerDistributionDouble, aPowerDistribution);
+    doubleArrayForDistribution(smo2DistributionDouble, smo2Distribution);
 }
 
 int
@@ -449,6 +453,7 @@ RideFileCache::decimalsFor(RideFile::SeriesType series)
         case RideFile::vam : return 0; break;
         case RideFile::wattsKg : return 2; break;
         case RideFile::aPower : return 0; break;
+        case RideFile::smo2 : return 0; break;
         case RideFile::lrbalance : return 1; break;
         case RideFile::wprime :  return 0; break;
         case RideFile::none : break;
@@ -637,6 +642,10 @@ RideFileCache::distributionArray(RideFile::SeriesType series)
             return aPowerDistributionDouble;
             break;
 
+        case RideFile::smo2:
+            return smo2DistributionDouble;
+            break;
+
         case RideFile::wattsKg:
             return wattsKgDistributionDouble;
             break;
@@ -748,6 +757,7 @@ void RideFileCache::RideFileCache::compute()
     computeDistribution(kphDistribution, RideFile::kph);
     computeDistribution(wattsKgDistribution, RideFile::wattsKg);
     computeDistribution(aPowerDistribution, RideFile::aPower);
+    computeDistribution(smo2Distribution, RideFile::smo2);
 
     // wait for them threads
     thread1.wait();
@@ -1320,6 +1330,7 @@ RideFileCache::computeDistribution(QVector<float> &array, RideFile::SeriesType s
         int offset = lvalue - min;
         if (offset >= 0 && offset < array.size()) array[offset] += ride->recIntSecs();
     }
+if (series == RideFile::smo2) qDebug()<<"smo2 array="<<array;
 }
 
 //
@@ -1400,6 +1411,7 @@ RideFileCache::RideFileCache(Context *context, QDate start, QDate end, bool filt
     npDistribution.resize(0);
     wattsKgDistribution.resize(0);
     aPowerDistribution.resize(0);
+    smo2Distribution.resize(0);
 
     // time in zone are fixed to 10 zone max
     wattsTimeInZone.resize(10);
@@ -1454,6 +1466,7 @@ RideFileCache::RideFileCache(Context *context, QDate start, QDate end, bool filt
             distAggregate(npDistributionDouble, rideCache.npDistributionDouble);
             distAggregate(wattsKgDistributionDouble, rideCache.wattsKgDistributionDouble);
             distAggregate(aPowerDistributionDouble, rideCache.aPowerDistributionDouble);
+            distAggregate(smo2DistributionDouble, rideCache.smo2DistributionDouble);
 
             // cumulate timeinzones
             for (int i=0; i<10; i++) {
@@ -1562,6 +1575,7 @@ RideFileCache::serialize(QDataStream *out)
     head.kphDistCount = kphDistribution.size();
     head.wattsKgDistCount = wattsKgDistribution.size();
     head.aPowerDistCount = aPowerDistribution.size();
+    head.smo2DistCount = smo2Distribution.size();
 
     out->writeRawData((const char *) &head, sizeof(head));
 
@@ -1593,6 +1607,7 @@ RideFileCache::serialize(QDataStream *out)
     out->writeRawData((const char *) npDistribution.data(), sizeof(float) * npDistribution.size());
     out->writeRawData((const char *) wattsKgDistribution.data(), sizeof(float) * wattsKgDistribution.size());
     out->writeRawData((const char *) aPowerDistribution.data(), sizeof(float) * aPowerDistribution.size());
+    out->writeRawData((const char *) smo2Distribution.data(), sizeof(float) * smo2Distribution.size());
 
     // time in zone
     out->writeRawData((const char *) wattsTimeInZone.data(), sizeof(float) * wattsTimeInZone.size());
@@ -1641,6 +1656,7 @@ RideFileCache::readCache()
         npDistribution.resize(head.npDistCount);
         wattsKgDistribution.resize(head.wattsKgDistCount);
         aPowerDistribution.resize(head.aPowerDistCount);
+        smo2Distribution.resize(head.smo2DistCount);
 
         // read in the arrays
         inFile.readRawData((char *) wattsMeanMax.data(), sizeof(float) * wattsMeanMax.size());
@@ -1671,6 +1687,7 @@ RideFileCache::readCache()
         inFile.readRawData((char *) npDistribution.data(), sizeof(float) * npDistribution.size());
         inFile.readRawData((char *) wattsKgDistribution.data(), sizeof(float) * wattsKgDistribution.size());
         inFile.readRawData((char *) aPowerDistribution.data(), sizeof(float) * aPowerDistribution.size());
+        inFile.readRawData((char *) smo2Distribution.data(), sizeof(float) * smo2Distribution.size());
 
         // time in zone
         inFile.readRawData((char *) wattsTimeInZone.data(), sizeof(float) * 10);
@@ -1707,6 +1724,7 @@ RideFileCache::readCache()
         doubleArrayForDistribution(npDistributionDouble, npDistribution);
         doubleArrayForDistribution(wattsKgDistributionDouble, wattsKgDistribution);
         doubleArrayForDistribution(aPowerDistributionDouble, aPowerDistribution);
+        doubleArrayForDistribution(smo2DistributionDouble, smo2Distribution);
 
         cacheFile.close();
     }
diff --git a/src/RideFileCache.h b/src/RideFileCache.h
index 14a937f40..c16348bbf 100644
--- a/src/RideFileCache.h
+++ b/src/RideFileCache.h
@@ -40,7 +40,7 @@ typedef double data_t;
 // arrays when plotting CP curves and histograms. It is precoputed
 // to save time and cached in a file .cpx
 //
-static const unsigned int RideFileCacheVersion = 20;
+static const unsigned int RideFileCacheVersion = 21;
 // revision history:
 // version  date         description
 // 1        29-Apr-11    Initial - header, mean-max & distribution data blocks
@@ -62,6 +62,7 @@ static const unsigned int RideFileCacheVersion = 20;
 // 18       19-Oct-14    Added gearRatio distribution
 // 19       11-Nov-14    Added Pace Zones distribution
 // 20       17-Nov-14    Added Polarized Zones for HR and Pace
+// 21       27-Nov-14    Added SmO2 distribution 
 
 // The cache file (.cpx) has a binary format:
 // 1 x Header data - describing the version and contents of the cache
@@ -102,7 +103,8 @@ struct RideFileCacheHeader {
                  xPowerDistCount,
                  npDistCount,
                  wattsKgDistCount,
-                 aPowerDistCount;
+                 aPowerDistCount,
+                 smo2DistCount;
 
     int LTHR, // used to calculate Time in Zone (TIZ)
         CP;   // used to calculate Time in Zone (TIZ)
@@ -298,6 +300,7 @@ class RideFileCache
         QVector<float> npDistribution; // RideFile::kph
         QVector<float> wattsKgDistribution; // RideFile::wattsKg
         QVector<float> aPowerDistribution; // RideFile::aPower
+        QVector<float> smo2Distribution; // RideFile::smo2
 
         QVector<double> wattsDistributionDouble; // RideFile::watts
         QVector<double> hrDistributionDouble; // RideFile::hr
@@ -309,6 +312,7 @@ class RideFileCache
         QVector<double> npDistributionDouble; // RideFile::np
         QVector<double> wattsKgDistributionDouble; // RideFile::wattsKg
         QVector<double> aPowerDistributionDouble; // RideFile::aPower
+        QVector<double> smo2DistributionDouble; // RideFile::aPower
 
 
         QVector<float> wattsTimeInZone;   // time in zone in seconds