diff --git a/doc/src/fix_adapt.rst b/doc/src/fix_adapt.rst
index 2b39917d86..a6c07fad4d 100644
--- a/doc/src/fix_adapt.rst
+++ b/doc/src/fix_adapt.rst
@@ -14,7 +14,7 @@ Syntax
 * adapt = style name of this fix command
 * N = adapt simulation settings every this many timesteps
 * one or more attribute/arg pairs may be appended
-* attribute = *pair* or *bond* or *angle* or *kspace* or *atom*
+* attribute = *pair* or *bond* or *angle* or *improper* or *kspace* or *atom*
 
   .. parsed-literal::
 
@@ -33,6 +33,11 @@ Syntax
          aparam = parameter to adapt over time
          I = type angle to set parameter for (integer or type label)
          v_name = variable with name that calculates value of aparam
+       *improper* args = istyle iparam I v_name
+         istyle = improper style name (e.g., cvff)
+         iparam = parameter to adapt over time
+         I = type improper to set parameter for (integer or type label)
+         v_name = variable with name that calculates value of iparam
        *kspace* arg = v_name
          v_name = variable with name that calculates scale factor on :math:`k`-space terms
        *atom* args = atomparam v_name
@@ -428,6 +433,56 @@ this fix uses to reset theta0 needs to generate values in radians.
 
 ----------
 
+.. versionadded:: TBD
+
+The *improper* keyword uses the specified variable to change the value of
+an improper coefficient over time, very similar to how the *angle* keyword
+operates. The only difference is that now an improper coefficient for a
+given improper type is adapted.
+
+A wild-card asterisk can be used in place of or in conjunction with the
+improper type argument to set the coefficients for multiple improper types.
+This takes the form "\*" or "\*n" or "m\*" or "m\*n".  If :math:`N` is
+the number of improper types, then an asterisk with no numeric values means
+all types from 1 to :math:`N`.  A leading asterisk means all types from
+1 to n (inclusive).  A trailing asterisk means all types from m to
+:math:`N` (inclusive).  A middle asterisk means all types from m to n
+(inclusive).
+
+If :doc:`improper_style hybrid <improper_hybrid>` is used, *istyle* should be a
+sub-style name. The improper styles that currently work with fix adapt are:
+
++---------------------------------------------------------+----------------+----------------+
+| :doc:`amoeba <improper_amoeba>`                         | k              | type impropers |
++---------------------------------------------------------+----------------+----------------+
+| :doc:`class2 <improper_class2>`                         | k,chi0         | type impropers |
++---------------------------------------------------------+----------------+----------------+
+| :doc:`cossq <improper_cossq>`                           | k,chi0         | type impropers |
++---------------------------------------------------------+----------------+----------------+
+| :doc:`cvff <improper_cvff>`                             | k,d,n          | type impropers |
++---------------------------------------------------------+----------------+----------------+
+| :doc:`distance <improper_distance>`                     | k2,k4          | type impropers |
++---------------------------------------------------------+----------------+----------------+
+| :doc:`distharm <improper_distharm>`                     | k,d0           | type impropers |
++---------------------------------------------------------+----------------+----------------+
+| :doc:`fourier <improper_fourier>`                       | k,C0,C1,C2     | type impropers |
++---------------------------------------------------------+----------------+----------------+
+| :doc:`harmonic <improper_harmonic>`                     | k,chi0         | type impropers |
++---------------------------------------------------------+----------------+----------------+
+| :doc:`inversion/harmonic <improper_inversion_harmonic>` | k,w0           | type impropers |
++---------------------------------------------------------+----------------+----------------+
+| :doc:`ring <improper_ring>`                             | k,theta0       | type impropers |
++---------------------------------------------------------+----------------+----------------+
+| :doc:`umbrella <improper_umbrella>`                     | k,w0           | type impropers |
++---------------------------------------------------------+----------------+----------------+
+| :doc:`sqdistharm <improper_sqdistharm>`                 | k              | type impropers |
++---------------------------------------------------------+----------------+----------------+
+
+Note that internally, chi0 and theta0 are stored in radians, so the variable
+this fix use to reset chi0 or theta0 needs to generate values in radians.
+
+----------
+
 The *kspace* keyword used the specified variable as a scale factor on
 the energy, forces, virial calculated by whatever :math:`k`-space solver is
 defined by the :doc:`kspace_style <kspace_style>` command.  If the
diff --git a/src/AMOEBA/improper_amoeba.cpp b/src/AMOEBA/improper_amoeba.cpp
index f14713cd20..d8b00888f5 100644
--- a/src/AMOEBA/improper_amoeba.cpp
+++ b/src/AMOEBA/improper_amoeba.cpp
@@ -337,3 +337,14 @@ void ImproperAmoeba::write_data(FILE *fp)
   for (int i = 1; i <= atom->nimpropertypes; i++)
     fprintf(fp,"%d %g\n",i,k[i]);
 }
+
+/* ----------------------------------------------------------------------
+   return ptr to internal members upon request
+------------------------------------------------------------------------ */
+
+void *ImproperAmoeba::extract(const char *str, int &dim)
+{
+  dim = 1;
+  if (strcmp(str, "k") == 0) return (void *) k;
+  return nullptr;
+}
diff --git a/src/AMOEBA/improper_amoeba.h b/src/AMOEBA/improper_amoeba.h
index d5a783a82f..f997b61629 100644
--- a/src/AMOEBA/improper_amoeba.h
+++ b/src/AMOEBA/improper_amoeba.h
@@ -34,6 +34,7 @@ class ImproperAmoeba : public Improper {
   void write_restart(FILE *) override;
   void read_restart(FILE *) override;
   void write_data(FILE *) override;
+  void *extract(const char *, int &) override;
 
  protected:
   int disable;
diff --git a/src/CLASS2/improper_class2.cpp b/src/CLASS2/improper_class2.cpp
index e53b06969c..20e1670f92 100644
--- a/src/CLASS2/improper_class2.cpp
+++ b/src/CLASS2/improper_class2.cpp
@@ -843,3 +843,15 @@ void ImproperClass2::write_data(FILE *fp)
             aa_theta0_1[i]*180.0/MY_PI,aa_theta0_2[i]*180.0/MY_PI,
             aa_theta0_3[i]*180.0/MY_PI);
 }
+
+/* ----------------------------------------------------------------------
+   return ptr to internal members upon request
+------------------------------------------------------------------------ */
+
+void *ImproperClass2::extract(const char *str, int &dim)
+{
+  dim = 1;
+  if (strcmp(str, "k") == 0) return (void *) k0;
+  if (strcmp(str, "chi0") == 0) return (void *) chi0;
+  return nullptr;
+}
diff --git a/src/CLASS2/improper_class2.h b/src/CLASS2/improper_class2.h
index 6102ef945c..3e30c8be53 100644
--- a/src/CLASS2/improper_class2.h
+++ b/src/CLASS2/improper_class2.h
@@ -33,6 +33,7 @@ class ImproperClass2 : public Improper {
   void write_restart(FILE *) override;
   void read_restart(FILE *) override;
   void write_data(FILE *) override;
+  void *extract(const char *, int &) override;
 
  protected:
   double *k0, *chi0;
diff --git a/src/EXTRA-MOLECULE/improper_cossq.cpp b/src/EXTRA-MOLECULE/improper_cossq.cpp
index 5d7a425217..e68930a9d8 100644
--- a/src/EXTRA-MOLECULE/improper_cossq.cpp
+++ b/src/EXTRA-MOLECULE/improper_cossq.cpp
@@ -309,3 +309,15 @@ void ImproperCossq::write_data(FILE *fp)
   for (int i = 1; i <= atom->nimpropertypes; i++)
     fprintf(fp,"%d %g %g\n",i,k[i],chi[i]/MY_PI*180.0);
 }
+
+/* ----------------------------------------------------------------------
+   return ptr to internal members upon request
+------------------------------------------------------------------------ */
+
+void *ImproperCossq::extract(const char *str, int &dim)
+{
+  dim = 1;
+  if (strcmp(str, "k") == 0) return (void *) k;
+  if (strcmp(str, "chi0") == 0) return (void *) chi;
+  return nullptr;
+}
diff --git a/src/EXTRA-MOLECULE/improper_cossq.h b/src/EXTRA-MOLECULE/improper_cossq.h
index cc7e94ca5c..bcc12e654f 100644
--- a/src/EXTRA-MOLECULE/improper_cossq.h
+++ b/src/EXTRA-MOLECULE/improper_cossq.h
@@ -33,6 +33,7 @@ class ImproperCossq : public Improper {
   void write_restart(FILE *) override;
   void read_restart(FILE *) override;
   void write_data(FILE *) override;
+  void *extract(const char *, int &) override;
 
  protected:
   double *k, *chi;
diff --git a/src/EXTRA-MOLECULE/improper_distance.cpp b/src/EXTRA-MOLECULE/improper_distance.cpp
index b8376020dd..ec55abaf2b 100644
--- a/src/EXTRA-MOLECULE/improper_distance.cpp
+++ b/src/EXTRA-MOLECULE/improper_distance.cpp
@@ -268,3 +268,16 @@ void ImproperDistance::write_data(FILE *fp)
   for (int i = 1; i <= atom->nimpropertypes; i++)
     fprintf(fp,"%d %g %g\n",i,k[i],chi[i]);
 }
+
+
+/* ----------------------------------------------------------------------
+   return ptr to internal members upon request
+------------------------------------------------------------------------ */
+
+void *ImproperDistance::extract(const char *str, int &dim)
+{
+  dim = 1;
+  if (strcmp(str, "k2") == 0) return (void *) k;
+  if (strcmp(str, "k4") == 0) return (void *) chi;
+  return nullptr;
+}
diff --git a/src/EXTRA-MOLECULE/improper_distance.h b/src/EXTRA-MOLECULE/improper_distance.h
index b0bfaea6e6..67d5cacc46 100644
--- a/src/EXTRA-MOLECULE/improper_distance.h
+++ b/src/EXTRA-MOLECULE/improper_distance.h
@@ -33,6 +33,7 @@ class ImproperDistance : public Improper {
   void write_restart(FILE *) override;
   void read_restart(FILE *) override;
   void write_data(FILE *) override;
+  void *extract(const char *, int &) override;
 
  private:
   double *k, *chi;
diff --git a/src/EXTRA-MOLECULE/improper_fourier.cpp b/src/EXTRA-MOLECULE/improper_fourier.cpp
index b2814f4d1f..350612a559 100644
--- a/src/EXTRA-MOLECULE/improper_fourier.cpp
+++ b/src/EXTRA-MOLECULE/improper_fourier.cpp
@@ -337,3 +337,17 @@ void ImproperFourier::write_data(FILE *fp)
   for (int i = 1; i <= atom->nimpropertypes; i++)
     fprintf(fp,"%d %g %g %g %g %d\n",i,k[i],C0[i],C1[i],C2[i],all[i]);
 }
+
+/* ----------------------------------------------------------------------
+   return ptr to internal members upon request
+------------------------------------------------------------------------ */
+
+void *ImproperFourier::extract(const char *str, int &dim)
+{
+  dim = 1;
+  if (strcmp(str, "k") == 0) return (void *) k;
+  if (strcmp(str, "C0") == 0) return (void *) C0;
+  if (strcmp(str, "C1") == 0) return (void *) C1;
+  if (strcmp(str, "C2") == 0) return (void *) C2;
+  return nullptr;
+}
diff --git a/src/EXTRA-MOLECULE/improper_fourier.h b/src/EXTRA-MOLECULE/improper_fourier.h
index 96354b6818..a4ec0d6096 100644
--- a/src/EXTRA-MOLECULE/improper_fourier.h
+++ b/src/EXTRA-MOLECULE/improper_fourier.h
@@ -33,6 +33,7 @@ class ImproperFourier : public Improper {
   void write_restart(FILE *) override;
   void read_restart(FILE *) override;
   void write_data(FILE *) override;
+  void *extract(const char *, int &) override;
 
  protected:
   double *k, *C0, *C1, *C2;
diff --git a/src/EXTRA-MOLECULE/improper_ring.cpp b/src/EXTRA-MOLECULE/improper_ring.cpp
index 57adb50260..7595a25c64 100644
--- a/src/EXTRA-MOLECULE/improper_ring.cpp
+++ b/src/EXTRA-MOLECULE/improper_ring.cpp
@@ -339,3 +339,16 @@ void ImproperRing::write_data(FILE *fp)
   for (int i = 1; i <= atom->nimpropertypes; i++)
     fprintf(fp,"%d %g %g\n",i,k[i],acos(chi[i])/MY_PI*180.0);
 }
+
+
+/* ----------------------------------------------------------------------
+   return ptr to internal members upon request
+------------------------------------------------------------------------ */
+
+void *ImproperRing::extract(const char *str, int &dim)
+{
+  dim = 1;
+  if (strcmp(str, "k") == 0) return (void *) k;
+  if (strcmp(str, "theta0") == 0) return (void *) chi;
+  return nullptr;
+}
diff --git a/src/EXTRA-MOLECULE/improper_ring.h b/src/EXTRA-MOLECULE/improper_ring.h
index db8a681f75..0c68b4e15a 100644
--- a/src/EXTRA-MOLECULE/improper_ring.h
+++ b/src/EXTRA-MOLECULE/improper_ring.h
@@ -33,6 +33,7 @@ class ImproperRing : public Improper {
   void write_restart(FILE *) override;
   void read_restart(FILE *) override;
   void write_data(FILE *) override;
+  void *extract(const char *, int &) override;
 
  protected:
   double *k, *chi;
diff --git a/src/MOFFF/improper_inversion_harmonic.cpp b/src/MOFFF/improper_inversion_harmonic.cpp
index 0a4661c6b1..7e51d4338c 100644
--- a/src/MOFFF/improper_inversion_harmonic.cpp
+++ b/src/MOFFF/improper_inversion_harmonic.cpp
@@ -332,3 +332,15 @@ void ImproperInversionHarmonic::write_data(FILE *fp)
   for (int i = 1; i <= atom->nimpropertypes; i++)
     fprintf(fp,"%d %g %g\n",i,kw[i],w0[i]/MY_PI*180.0);
 }
+
+/* ----------------------------------------------------------------------
+   return ptr to internal members upon request
+------------------------------------------------------------------------ */
+
+void *ImproperInversionHarmonic::extract(const char *str, int &dim)
+{
+  dim = 1;
+  if (strcmp(str, "k") == 0) return (void *) kw;
+  if (strcmp(str, "w0") == 0) return (void *) w0;
+  return nullptr;
+}
diff --git a/src/MOFFF/improper_inversion_harmonic.h b/src/MOFFF/improper_inversion_harmonic.h
index 2ad1bceba1..eabb91194f 100644
--- a/src/MOFFF/improper_inversion_harmonic.h
+++ b/src/MOFFF/improper_inversion_harmonic.h
@@ -33,6 +33,7 @@ class ImproperInversionHarmonic : public Improper {
   void write_restart(FILE *) override;
   void read_restart(FILE *) override;
   void write_data(FILE *) override;
+  void *extract(const char *, int &) override;
 
  protected:
   double *kw, *w0;
diff --git a/src/MOLECULE/improper_cvff.cpp b/src/MOLECULE/improper_cvff.cpp
index 11dace26d1..480d106549 100644
--- a/src/MOLECULE/improper_cvff.cpp
+++ b/src/MOLECULE/improper_cvff.cpp
@@ -337,3 +337,16 @@ void ImproperCvff::write_data(FILE *fp)
   for (int i = 1; i <= atom->nimpropertypes; i++)
     fprintf(fp, "%d %g %d %d\n", i, k[i], sign[i], multiplicity[i]);
 }
+
+/* ----------------------------------------------------------------------
+   return ptr to internal members upon request
+------------------------------------------------------------------------ */
+
+void *ImproperCvff::extract(const char *str, int &dim)
+{
+  dim = 1;
+  if (strcmp(str, "k") == 0) return (void *) k;
+  if (strcmp(str, "d") == 0) return (void *) sign;
+  if (strcmp(str, "n") == 0) return (void *) multiplicity;
+  return nullptr;
+}
diff --git a/src/MOLECULE/improper_cvff.h b/src/MOLECULE/improper_cvff.h
index ff550fe9e8..07ff607417 100644
--- a/src/MOLECULE/improper_cvff.h
+++ b/src/MOLECULE/improper_cvff.h
@@ -33,6 +33,7 @@ class ImproperCvff : public Improper {
   void write_restart(FILE *) override;
   void read_restart(FILE *) override;
   void write_data(FILE *) override;
+  void *extract(const char *, int &) override;
 
  protected:
   double *k;
diff --git a/src/MOLECULE/improper_harmonic.cpp b/src/MOLECULE/improper_harmonic.cpp
index 5f25d678db..02a9d7a60d 100644
--- a/src/MOLECULE/improper_harmonic.cpp
+++ b/src/MOLECULE/improper_harmonic.cpp
@@ -276,3 +276,15 @@ void ImproperHarmonic::write_data(FILE *fp)
   for (int i = 1; i <= atom->nimpropertypes; i++)
     fprintf(fp, "%d %g %g\n", i, k[i], RAD2DEG * chi[i]);
 }
+
+/* ----------------------------------------------------------------------
+   return ptr to internal members upon request
+------------------------------------------------------------------------ */
+
+void *ImproperHarmonic::extract(const char *str, int &dim)
+{
+  dim = 1;
+  if (strcmp(str, "k") == 0) return (void *) k;
+  if (strcmp(str, "chi0") == 0) return (void *) chi;
+  return nullptr;
+}
diff --git a/src/MOLECULE/improper_harmonic.h b/src/MOLECULE/improper_harmonic.h
index 89ebe49dec..a0047c28f2 100644
--- a/src/MOLECULE/improper_harmonic.h
+++ b/src/MOLECULE/improper_harmonic.h
@@ -33,6 +33,7 @@ class ImproperHarmonic : public Improper {
   void write_restart(FILE *) override;
   void read_restart(FILE *) override;
   void write_data(FILE *) override;
+  void *extract(const char *, int &) override;
 
  protected:
   double *k, *chi;
diff --git a/src/MOLECULE/improper_umbrella.cpp b/src/MOLECULE/improper_umbrella.cpp
index d3dcf4da41..3c8e2c0d93 100644
--- a/src/MOLECULE/improper_umbrella.cpp
+++ b/src/MOLECULE/improper_umbrella.cpp
@@ -322,3 +322,16 @@ void ImproperUmbrella::write_data(FILE *fp)
   for (int i = 1; i <= atom->nimpropertypes; i++)
     fprintf(fp, "%d %g %g\n", i, kw[i], RAD2DEG * w0[i]);
 }
+
+
+/* ----------------------------------------------------------------------
+   return ptr to internal members upon request
+------------------------------------------------------------------------ */
+
+void *ImproperUmbrella::extract(const char *str, int &dim)
+{
+  dim = 1;
+  if (strcmp(str, "k") == 0) return (void *) kw;
+  if (strcmp(str, "w0") == 0) return (void *) w0;
+  return nullptr;
+}
diff --git a/src/MOLECULE/improper_umbrella.h b/src/MOLECULE/improper_umbrella.h
index 9441810861..a6791ffe20 100644
--- a/src/MOLECULE/improper_umbrella.h
+++ b/src/MOLECULE/improper_umbrella.h
@@ -33,6 +33,7 @@ class ImproperUmbrella : public Improper {
   void write_restart(FILE *) override;
   void read_restart(FILE *) override;
   void write_data(FILE *) override;
+  void *extract(const char *, int &) override;
 
  protected:
   double *kw, *w0, *C;
diff --git a/src/YAFF/improper_distharm.cpp b/src/YAFF/improper_distharm.cpp
index c056b310ee..69d14cc997 100644
--- a/src/YAFF/improper_distharm.cpp
+++ b/src/YAFF/improper_distharm.cpp
@@ -226,12 +226,9 @@ void ImproperDistHarm::coeff(int narg, char **arg)
   double k_one = utils::numeric(FLERR,arg[1],false,lmp);
   double chi_one = utils::numeric(FLERR,arg[2],false,lmp);
 
-  // convert chi from degrees to radians
-
   int count = 0;
   for (int i = ilo; i <= ihi; i++) {
     k[i] = k_one;
-    //chi[i] = chi_one/180.0 * PI;
     chi[i] = chi_one;
     setflag[i] = 1;
     count++;
@@ -267,3 +264,15 @@ void ImproperDistHarm::read_restart(FILE *fp)
 
   for (int i = 1; i <= atom->nimpropertypes; i++) setflag[i] = 1;
 }
+
+/* ----------------------------------------------------------------------
+   return ptr to internal members upon request
+------------------------------------------------------------------------ */
+
+void *ImproperDistHarm::extract(const char *str, int &dim)
+{
+  dim = 1;
+  if (strcmp(str, "k") == 0) return (void *) k;
+  if (strcmp(str, "d0") == 0) return (void *) chi;
+  return nullptr;
+}
diff --git a/src/YAFF/improper_distharm.h b/src/YAFF/improper_distharm.h
index 911bbadb0d..6896af3e15 100644
--- a/src/YAFF/improper_distharm.h
+++ b/src/YAFF/improper_distharm.h
@@ -32,6 +32,7 @@ class ImproperDistHarm : public Improper {
   void coeff(int, char **) override;
   void write_restart(FILE *) override;
   void read_restart(FILE *) override;
+  void *extract(const char *, int &) override;
 
  private:
   double *k, *chi;
diff --git a/src/YAFF/improper_sqdistharm.cpp b/src/YAFF/improper_sqdistharm.cpp
index f3a34f3976..1981c61f38 100644
--- a/src/YAFF/improper_sqdistharm.cpp
+++ b/src/YAFF/improper_sqdistharm.cpp
@@ -267,3 +267,14 @@ void ImproperSQDistHarm::read_restart(FILE *fp)
 
   for (int i = 1; i <= atom->nimpropertypes; i++) setflag[i] = 1;
 }
+
+/* ----------------------------------------------------------------------
+   return ptr to internal members upon request
+------------------------------------------------------------------------ */
+
+void *ImproperSQDistHarm::extract(const char *str, int &dim)
+{
+  dim = 1;
+  if (strcmp(str, "k") == 0) return (void *) k;
+  return nullptr;
+}
diff --git a/src/YAFF/improper_sqdistharm.h b/src/YAFF/improper_sqdistharm.h
index 4cd89a294e..d8d4131362 100644
--- a/src/YAFF/improper_sqdistharm.h
+++ b/src/YAFF/improper_sqdistharm.h
@@ -32,6 +32,7 @@ class ImproperSQDistHarm : public Improper {
   void coeff(int, char **) override;
   void write_restart(FILE *) override;
   void read_restart(FILE *) override;
+  void *extract(const char *, int &) override;
 
  private:
   double *k, *chi;
diff --git a/src/fix_adapt.cpp b/src/fix_adapt.cpp
index 418e2e4a80..eb7125caf7 100644
--- a/src/fix_adapt.cpp
+++ b/src/fix_adapt.cpp
@@ -24,6 +24,8 @@
 #include "fix_store_atom.h"
 #include "force.h"
 #include "group.h"
+#include "improper.h"
+#include "improper_hybrid.h"
 #include "input.h"
 #include "kspace.h"
 #include "math_const.h"
@@ -41,14 +43,14 @@ using namespace LAMMPS_NS;
 using namespace FixConst;
 using namespace MathConst;
 
-enum{PAIR, KSPACE, ATOM, BOND, ANGLE};
+enum{PAIR, KSPACE, ATOM, BOND, ANGLE, IMPROPER};
 enum{DIAMETER, CHARGE};
 
 /* ---------------------------------------------------------------------- */
 
 FixAdapt::FixAdapt(LAMMPS *lmp, int narg, char **arg) :
   Fix(lmp, narg, arg), nadapt(0), anypair(0), anybond(0), anyangle(0),
-  id_fix_diam(nullptr), id_fix_chg(nullptr), adapt(nullptr)
+  anyimproper(0), id_fix_diam(nullptr), id_fix_chg(nullptr), adapt(nullptr)
 {
   if (narg < 5) utils::missing_cmd_args(FLERR,"fix adapt", error);
   nevery = utils::inumeric(FLERR,arg[3],false,lmp);
@@ -83,6 +85,10 @@ FixAdapt::FixAdapt(LAMMPS *lmp, int narg, char **arg) :
       if (iarg+5 > narg) utils::missing_cmd_args(FLERR,"fix adapt angle", error);
       nadapt++;
       iarg += 5;
+    } else if (strcmp(arg[iarg],"improper") == 0) {
+      if (iarg+5 > narg) utils::missing_cmd_args(FLERR,"fix adapt improper", error);
+      nadapt++;
+      iarg += 5;
     } else break;
   }
 
@@ -149,6 +155,19 @@ FixAdapt::FixAdapt(LAMMPS *lmp, int narg, char **arg) :
       nadapt++;
       iarg += 5;
 
+    } else if (strcmp(arg[iarg],"improper") == 0) {
+      adapt[nadapt].which = IMPROPER;
+      adapt[nadapt].improper = nullptr;
+      adapt[nadapt].istyle = utils::strdup(arg[iarg+1]);
+      adapt[nadapt].iparam = utils::strdup(arg[iarg+2]);
+      utils::bounds_typelabel(FLERR, arg[iarg+3], 1, atom->nimpropertypes,
+                              adapt[nadapt].ilo, adapt[nadapt].ihi, lmp, Atom::IMPROPER);
+      if (utils::strmatch(arg[iarg+4],"^v_")) {
+        adapt[nadapt].var = utils::strdup(arg[iarg+4]+2);
+      } else error->all(FLERR,"Argument #{} must be variable not {}", iarg+5, arg[iarg+4]);
+      nadapt++;
+      iarg += 5;
+
     } else if (strcmp(arg[iarg],"kspace") == 0) {
       adapt[nadapt].which = KSPACE;
       if (utils::strmatch(arg[iarg+1],"^v_")) {
@@ -224,6 +243,13 @@ FixAdapt::FixAdapt(LAMMPS *lmp, int narg, char **arg) :
   n = atom->nangletypes;
   for (int m = 0; m < nadapt; ++m)
     if (adapt[m].which == ANGLE) memory->create(adapt[m].vector_orig,n+1,"adapt:vector_orig");
+
+  // allocate improper style arrays:
+
+  n = atom->nimpropertypes;
+  for (int m = 0; m < nadapt; ++m)
+    if (adapt[m].which == IMPROPER) memory->create(adapt[m].vector_orig,n+1,"adapt:vector_orig");
+
 }
 
 /* ---------------------------------------------------------------------- */
@@ -244,6 +270,10 @@ FixAdapt::~FixAdapt()
       delete[] adapt[m].astyle;
       delete[] adapt[m].aparam;
       memory->destroy(adapt[m].vector_orig);
+    } else if (adapt[m].which == IMPROPER) {
+      delete[] adapt[m].istyle;
+      delete[] adapt[m].iparam;
+      memory->destroy(adapt[m].vector_orig);
     }
   }
   delete[] adapt;
@@ -338,6 +368,7 @@ void FixAdapt::init()
   anypair = 0;
   anybond = 0;
   anyangle = 0;
+  anyimproper = 0;
 
   for (int m = 0; m < nadapt; m++) {
     Adapt *ad = &adapt[m];
@@ -478,6 +509,40 @@ void FixAdapt::init()
 
       delete[] astyle;
 
+    } else if (ad->which == IMPROPER) {
+      ad->improper = nullptr;
+      anyimproper = 1;
+
+      char *istyle = utils::strdup(ad->istyle);
+      if (lmp->suffix_enable)
+        ad->improper = force->improper_match(fmt::format("{}/{}",istyle,lmp->suffix));
+
+      if (ad->improper == nullptr) ad->improper = force->improper_match(istyle);
+      if (ad->improper == nullptr )
+        error->all(FLERR,"Fix adapt improper style {} does not exist", istyle);
+
+      void *ptr = ad->improper->extract(ad->iparam,ad->idim);
+
+      if (ptr == nullptr)
+        error->all(FLERR,"Fix adapt improper style parameter {} not supported", ad->iparam);
+
+      // for improper styles, use a vector
+
+      if (ad->idim == 1) ad->vector = (double *) ptr;
+
+      if (utils::strmatch(force->improper_style,"^hybrid")) {
+        auto improper = dynamic_cast<ImproperHybrid *>(force->improper);
+        if (improper) {
+          for (i = ad->ilo; i <= ad->ihi; i++) {
+            if (!improper->check_itype(i,istyle))
+              error->all(FLERR,"Fix adapt type improper range is not valid "
+                         "for improper hybrid sub-style {}", istyle);
+          }
+        }
+      }
+
+      delete[] istyle;
+
     } else if (ad->which == KSPACE) {
       if (force->kspace == nullptr)
         error->all(FLERR, Error::NOLASTLINE,
@@ -504,7 +569,7 @@ void FixAdapt::init()
 
   if (restart_reset) restart_reset = 0;
 
-  // make copy of original pair/bond/angle array values
+  // make copy of original pair/bond/angle/improper array values
 
   for (int m = 0; m < nadapt; m++) {
     Adapt *ad = &adapt[m];
@@ -522,6 +587,10 @@ void FixAdapt::init()
     } else if (ad->which == ANGLE && ad->adim == 1) {
       for (i = ad->ilo; i <= ad->ihi; ++i )
         ad->vector_orig[i] = ad->vector[i];
+
+    } else if (ad->which == IMPROPER && ad->idim == 1) {
+      for (i = ad->ilo; i <= ad->ihi; ++i )
+        ad->vector_orig[i] = ad->vector[i];
     }
 
   }
@@ -641,6 +710,18 @@ void FixAdapt::change_settings()
             ad->vector[i] = value;
       }
 
+    // set improper type array values:
+
+    } else if (ad->which == IMPROPER) {
+      if (ad->idim == 1) {
+        if (scaleflag)
+          for (i = ad->ilo; i <= ad->ihi; ++i )
+            ad->vector[i] = value*ad->vector_orig[i];
+        else
+          for (i = ad->ilo; i <= ad->ihi; ++i )
+            ad->vector[i] = value;
+      }
+
     // set kspace scale factor
 
     } else if (ad->which == KSPACE) {
@@ -716,6 +797,7 @@ void FixAdapt::change_settings()
   if (anypair) force->pair->reinit();
   if (anybond) force->bond->reinit();
   if (anyangle) force->angle->reinit();
+  if (anyimproper) force->improper->reinit();
 
   // reset KSpace charges if charges have changed
 
@@ -750,6 +832,12 @@ void FixAdapt::restore_settings()
           ad->vector[i] = ad->vector_orig[i];
       }
 
+    } else if (ad->which == IMPROPER) {
+      if (ad->idim == 1) {
+        for (int i = ad->ilo; i <= ad->ihi; i++)
+          ad->vector[i] = ad->vector_orig[i];
+      }
+
     } else if (ad->which == KSPACE) {
       *kspace_scale = 1.0;
 
@@ -790,6 +878,7 @@ void FixAdapt::restore_settings()
   if (anypair) force->pair->reinit();
   if (anybond) force->bond->reinit();
   if (anyangle) force->angle->reinit();
+  if (anyimproper) force->improper->reinit();
   if (chgflag && force->kspace) force->kspace->qsum_qsq();
 }
 
diff --git a/src/fix_adapt.h b/src/fix_adapt.h
index 20964a8b12..9f064a163e 100644
--- a/src/fix_adapt.h
+++ b/src/fix_adapt.h
@@ -44,7 +44,7 @@ class FixAdapt : public Fix {
 
  private:
   int nadapt, resetflag, scaleflag, massflag;
-  int anypair, anybond, anyangle;
+  int anypair, anybond, anyangle, anyimproper;
   int nlevels_respa;
   char *id_fix_diam, *id_fix_chg;
   class FixStoreAtom *fix_diam, *fix_chg;
@@ -57,8 +57,9 @@ class FixAdapt : public Fix {
     char *pstyle, *pparam;
     char *bstyle, *bparam;
     char *astyle, *aparam;
+    char *istyle, *iparam;
     int ilo, ihi, jlo, jhi;
-    int pdim, bdim, adim;
+    int pdim, bdim, adim, idim;
     double *scalar, scalar_orig;
     double *vector, *vector_orig;
     double **array, **array_orig;
@@ -66,6 +67,7 @@ class FixAdapt : public Fix {
     class Pair *pair;
     class Bond *bond;
     class Angle *angle;
+    class Improper *improper;
   };
 
   Adapt *adapt;
diff --git a/src/improper.cpp b/src/improper.cpp
index 02158dfff1..77570f565c 100644
--- a/src/improper.cpp
+++ b/src/improper.cpp
@@ -31,6 +31,7 @@ Improper::Improper(LAMMPS *_lmp) : Pointers(_lmp)
 {
   energy = 0.0;
   writedata = 0;
+  reinitflag = 1;
   for (int i = 0; i < 4; i++) symmatoms[i] = 0;
 
   allocated = 0;
@@ -427,3 +428,15 @@ double Improper::memory_usage()
   bytes += (double) comm->nthreads * maxvatom * 6 * sizeof(double);
   return bytes;
 }
+
+/* -----------------------------------------------------------------------
+   reset all type-based improper params via init()
+-------------------------------------------------------------------------- */
+
+void Improper::reinit()
+{
+  if (!reinitflag)
+    error->all(FLERR, "Fix adapt interface to this improper style not supported");
+
+  init();
+}
diff --git a/src/improper.h b/src/improper.h
index f65ba3bdbc..0f539bdece 100644
--- a/src/improper.h
+++ b/src/improper.h
@@ -37,6 +37,9 @@ class Improper : protected Pointers {
                              // CENTROID_AVAIL = different and implemented
                              // CENTROID_NOTAVAIL = different, not yet implemented
 
+  int reinitflag;    // 0 if not compatible with fix adapt
+                     // extract() method may still need to be added
+
   int symmatoms[4];    // symmetry atom(s) of improper style
                        // value of 0: interchangable atoms
                        // value of 1: central atom
@@ -67,6 +70,8 @@ class Improper : protected Pointers {
     du = 0.0;
     du2 = 0.0;
   }
+  virtual void *extract(const char *, int &) { return nullptr; }
+  void reinit();
 
  protected:
   int suffix_flag;    // suffix compatibility flag
diff --git a/src/improper_hybrid.cpp b/src/improper_hybrid.cpp
index 5337f062b4..1edfe5ceb7 100644
--- a/src/improper_hybrid.cpp
+++ b/src/improper_hybrid.cpp
@@ -320,6 +320,14 @@ void ImproperHybrid::init_style()
     if (styles[m]) styles[m]->init_style();
 }
 
+/* ---------------------------------------------------------------------- */
+
+int ImproperHybrid::check_itype(int itype, char *substyle)
+{
+  if (strcmp(keywords[map[itype]], substyle) == 0) return 1;
+  return 0;
+}
+
 /* ----------------------------------------------------------------------
    proc 0 writes to restart file
 ------------------------------------------------------------------------- */
diff --git a/src/improper_hybrid.h b/src/improper_hybrid.h
index 89a4664da2..86df8ea9d0 100644
--- a/src/improper_hybrid.h
+++ b/src/improper_hybrid.h
@@ -40,6 +40,8 @@ class ImproperHybrid : public Improper {
   void read_restart(FILE *) override;
   double memory_usage() override;
 
+  int check_itype(int, char *);
+
  protected:
   int *map;    // which style each improper type points to
 
diff --git a/unittest/force-styles/test_improper_style.cpp b/unittest/force-styles/test_improper_style.cpp
index e272033e85..4a8c3d5106 100644
--- a/unittest/force-styles/test_improper_style.cpp
+++ b/unittest/force-styles/test_improper_style.cpp
@@ -720,3 +720,44 @@ TEST(ImproperStyle, numdiff)
     cleanup_lammps(lmp, test_config);
     if (!verbose) ::testing::internal::GetCapturedStdout();
 }
+
+TEST(ImproperStyle, extract)
+{
+    if (test_config.skip_tests.count(test_info_->name())) GTEST_SKIP();
+
+    LAMMPS::argv args = {"ImproperStyle", "-log", "none", "-echo", "screen", "-nocite"};
+
+    if (!verbose) ::testing::internal::CaptureStdout();
+    LAMMPS *lmp = nullptr;
+    try {
+        lmp = init_lammps(args, test_config, true);
+    } catch (std::exception &e) {
+        if (!verbose) ::testing::internal::GetCapturedStdout();
+        FAIL() << e.what();
+    }
+    if (!verbose) ::testing::internal::GetCapturedStdout();
+
+    if (!lmp) {
+        std::cerr << "One or more prerequisite styles are not available "
+                     "in this LAMMPS configuration:\n";
+        for (auto prerequisite : test_config.prerequisites) {
+            std::cerr << prerequisite.first << "_style " << prerequisite.second << "\n";
+        }
+        GTEST_SKIP();
+    }
+
+    auto *improper = lmp->force->improper;
+    void *ptr   = nullptr;
+    int dim     = 0;
+    for (auto extract : test_config.extract) {
+        ptr = improper->extract(extract.first.c_str(), dim);
+        EXPECT_NE(ptr, nullptr);
+        EXPECT_EQ(dim, extract.second);
+    }
+    ptr = improper->extract("does_not_exist", dim);
+    EXPECT_EQ(ptr, nullptr);
+
+    if (!verbose) ::testing::internal::CaptureStdout();
+    cleanup_lammps(lmp, test_config);
+    if (!verbose) ::testing::internal::GetCapturedStdout();
+}
diff --git a/unittest/force-styles/tests/improper-class2.yaml b/unittest/force-styles/tests/improper-class2.yaml
index 4350441eeb..eba334a1e6 100644
--- a/unittest/force-styles/tests/improper-class2.yaml
+++ b/unittest/force-styles/tests/improper-class2.yaml
@@ -14,7 +14,9 @@ improper_coeff: ! |
   1  75.0 169
   2  45.0  10
   *  aa 75 42 31 125.4 130.01 115.06
-extract: ! ""
+extract: ! |
+  k 1
+  chi0 1
 natoms: 29
 init_energy: 1375.7372366975192
 init_stress: ! |-
diff --git a/unittest/force-styles/tests/improper-cossq.yaml b/unittest/force-styles/tests/improper-cossq.yaml
index 4faaa2214a..2e2767d368 100644
--- a/unittest/force-styles/tests/improper-cossq.yaml
+++ b/unittest/force-styles/tests/improper-cossq.yaml
@@ -13,7 +13,9 @@ improper_style: cossq
 improper_coeff: ! |
   1  75.0 120.2
   2  45.0  59.5
-extract: ! ""
+extract: ! |
+  k 1
+  chi0 1
 natoms: 29
 init_energy: 47.901206451962224
 init_stress: ! |-
diff --git a/unittest/force-styles/tests/improper-cvff.yaml b/unittest/force-styles/tests/improper-cvff.yaml
index 3a300de4d6..be18107884 100644
--- a/unittest/force-styles/tests/improper-cvff.yaml
+++ b/unittest/force-styles/tests/improper-cvff.yaml
@@ -13,7 +13,10 @@ improper_style: cvff
 improper_coeff: ! |
   1  75.0 -1 5
   2  45.0 +1 2
-extract: ! ""
+extract: ! |
+  k 1
+  d 1
+  n 1
 natoms: 29
 init_energy: 89.33266688553577
 init_stress: ! |2-
diff --git a/unittest/force-styles/tests/improper-distance.yaml b/unittest/force-styles/tests/improper-distance.yaml
index 91df7b7bae..3c64d4af52 100644
--- a/unittest/force-styles/tests/improper-distance.yaml
+++ b/unittest/force-styles/tests/improper-distance.yaml
@@ -13,7 +13,9 @@ improper_style: distance
 improper_coeff: ! |
   1  75.0 120.2
   2  45.0  59.5
-extract: ! ""
+extract: ! |
+  k2 1
+  k4 1
 natoms: 29
 init_energy: 0.0747454910197192
 init_stress: ! |-
diff --git a/unittest/force-styles/tests/improper-distharm.yaml b/unittest/force-styles/tests/improper-distharm.yaml
index e2916d3d74..1ae48c8488 100644
--- a/unittest/force-styles/tests/improper-distharm.yaml
+++ b/unittest/force-styles/tests/improper-distharm.yaml
@@ -13,7 +13,9 @@ improper_style: distharm
 improper_coeff: ! |
   1  75.0 5.5
   2  45.0 6.2
-extract: ! ""
+extract: ! |
+  k 1
+  d0 1
 natoms: 29
 init_energy: 3973.601605432119
 init_stress: ! |2-
diff --git a/unittest/force-styles/tests/improper-fourier.yaml b/unittest/force-styles/tests/improper-fourier.yaml
index 278698a190..096d9c0fa1 100644
--- a/unittest/force-styles/tests/improper-fourier.yaml
+++ b/unittest/force-styles/tests/improper-fourier.yaml
@@ -13,7 +13,11 @@ improper_style: fourier
 improper_coeff: ! |
   1  75.0 0.9 0.2 0.3 1
   2  45.0 0.5 0.1 0.8 0
-extract: ! ""
+extract: ! |
+  k 1
+  C0 1
+  C1 1
+  C2 1
 natoms: 29
 init_energy: 376.7915390602297
 init_stress: ! |2-
diff --git a/unittest/force-styles/tests/improper-harmonic.yaml b/unittest/force-styles/tests/improper-harmonic.yaml
index 7ac0dbe06e..7b2e14ee9e 100644
--- a/unittest/force-styles/tests/improper-harmonic.yaml
+++ b/unittest/force-styles/tests/improper-harmonic.yaml
@@ -13,7 +13,9 @@ improper_style: harmonic
 improper_coeff: ! |
   1  75.0 120.2
   2  45.0  59.5
-extract: ! ""
+extract: ! |
+  k 1
+  chi0 1
 natoms: 29
 init_energy: 369.34096479618404
 init_stress: ! |2-
diff --git a/unittest/force-styles/tests/improper-inversion_harmonic.yaml b/unittest/force-styles/tests/improper-inversion_harmonic.yaml
index 73eade4958..44fd09763d 100644
--- a/unittest/force-styles/tests/improper-inversion_harmonic.yaml
+++ b/unittest/force-styles/tests/improper-inversion_harmonic.yaml
@@ -13,7 +13,9 @@ improper_style: inversion/harmonic
 improper_coeff: ! |
   1  75.0 0.1
   2  45.0 1.0
-extract: ! ""
+extract: ! |
+  k 1
+  w0 1
 natoms: 29
 init_energy: 0.35230115027159387
 init_stress: ! |-
diff --git a/unittest/force-styles/tests/improper-ring.yaml b/unittest/force-styles/tests/improper-ring.yaml
index 6a824f9699..48cb944af3 100644
--- a/unittest/force-styles/tests/improper-ring.yaml
+++ b/unittest/force-styles/tests/improper-ring.yaml
@@ -13,7 +13,9 @@ improper_style: ring
 improper_coeff: ! |
   1  75.0 120.2
   2  45.0  59.5
-extract: ! ""
+extract: ! |
+  k 1
+  theta0 1
 natoms: 29
 init_energy: 31535.23771704055
 init_stress: ! |-
diff --git a/unittest/force-styles/tests/improper-sqdistharm.yaml b/unittest/force-styles/tests/improper-sqdistharm.yaml
index 8bf671efbd..7e08c86fc7 100644
--- a/unittest/force-styles/tests/improper-sqdistharm.yaml
+++ b/unittest/force-styles/tests/improper-sqdistharm.yaml
@@ -13,7 +13,8 @@ improper_style: sqdistharm
 improper_coeff: ! |
   1  75.0 5.5
   2  45.0 6.2
-extract: ! ""
+extract: ! |
+  k 1
 natoms: 29
 init_energy: 3997.62616072489
 init_stress: ! |2-
diff --git a/unittest/force-styles/tests/improper-umbrella.yaml b/unittest/force-styles/tests/improper-umbrella.yaml
index ff6822e9d8..61557813c8 100644
--- a/unittest/force-styles/tests/improper-umbrella.yaml
+++ b/unittest/force-styles/tests/improper-umbrella.yaml
@@ -13,7 +13,9 @@ improper_style: umbrella
 improper_coeff: ! |
   1  75.0 120.2
   2  45.0  59.5
-extract: ! ""
+extract: ! |
+  k 1
+  w0 1
 natoms: 29
 init_energy: 120.51735030260785
 init_stress: ! |2-