diff --git a/engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/SimpleActivity.java b/engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/SimpleActivity.java
index a05987550..2e36fa5b0 100644
--- a/engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/SimpleActivity.java
+++ b/engine-api/src/main/java/io/nosqlbench/engine/api/activityimpl/SimpleActivity.java
@@ -109,7 +109,7 @@ public class SimpleActivity implements Activity, ProgressCapable, ActivityDefObs
     }
 
     @Override
-    public void initActivity() {
+    public synchronized void initActivity() {
         initOrUpdateRateLimiters(this.activityDef);
     }
 
@@ -353,7 +353,7 @@ public class SimpleActivity implements Activity, ProgressCapable, ActivityDefObs
      *
      * @param seq - The {@link OpSequence} to derive the defaults from
      */
-    public void setDefaultsFromOpSequence(OpSequence<?> seq) {
+    public synchronized void setDefaultsFromOpSequence(OpSequence<?> seq) {
         Optional<String> strideOpt = getParams().getOptionalString("stride");
         if (strideOpt.isEmpty()) {
             String stride = String.valueOf(seq.getSequence().length);
diff --git a/engine-core/src/main/java/io/nosqlbench/engine/core/lifecycle/activity/ActivityExecutor.java b/engine-core/src/main/java/io/nosqlbench/engine/core/lifecycle/activity/ActivityExecutor.java
index a96556fa5..d4adc1616 100644
--- a/engine-core/src/main/java/io/nosqlbench/engine/core/lifecycle/activity/ActivityExecutor.java
+++ b/engine-core/src/main/java/io/nosqlbench/engine/core/lifecycle/activity/ActivityExecutor.java
@@ -417,7 +417,7 @@ public class ActivityExecutor implements ActivityController, ParameterMap.Listen
         }
     }
 
-    public void startActivity() {
+    public synchronized void startActivity() {
         // we need an executor service to run motor threads on
         startMotorExecutorService();
         startRunningActivityThreads();