American Endurance Ride Conference


held via telephone conference call

March 7, 2005


President C. Mike Tomlinson called the meeting to order at 6:02 pm.  Also on the line for the call:   Treasurer Terry Woolley Howe, Mike Jaffe, Roberta Harms, Connie Caudill, Howard Kent, Stan Eichelberger, Patti Pizzo, Gail Williams, Bob Morris, John Parke, Duane Barnett, Randy Eiland, Jim Baldwin, Dane Frazier, Mike Maul, Stagg Newman, Maggy Price, Robert Ribley, and Executive Director Kathleen A. Henkel.  Absent:  Vice President Susan Kasemeyer; Secretary Jan Jeffers; Vonita Bowers; Jan Stevens; Roger Taylor; Nick Warhol; Barney Fleming.


It was moved by Connie Caudill and seconded by Mike Maul to excuse Roger Taylor (out of the country); Jan Stevens (traveling); Vonita Bowers (traveling); Susan Kasemeyer (family concerns); Jan Jeffers, Nick Warhol from this call.  Motion passed.


It was moved by Robert Ribley and seconded by Bob Morris to approve the minutes of the February 7, 2005, call as written.  Motion passed.


It was moved by Stan Eichelberger and seconded by Mike Maul to accept the Education and Research Grants committee reports as written.  Motion passed.


Special Sanction Committee Chair Vonita Bowers was unable to make the call and President Tomlinson advised in her absence that the ride managers for the Grand Canyon XP and Owyhee Pioneer rides have agreed to hold their rides even though they overlap by one day this year.  Steps will be taken to insure the rides do not overlap next season.  No word from Vonita regarding a proposed date change for the Smokey Killen ride, West Region, which also overlapped with the Grand Canyon and Owyhee rides.
Research Grants Committee Chair Bob Morris advised he previously forwarded information regarding a grant from Virginia Tech at Middleburg in the amount of $16,500, presented by T. M. Hess, DVM.  Bob Morris advised the committee is in favor of the grant and there is a possibility of some assistance to AERC with the funding for the grant.  Motion before the board to seek approval of the grant passed with one abstention, Patti Pizzo.
President Tomlinson invited Tom Ackart, facilitator regarding the long range plan to join the call.  Tom introduced himself to the board and briefly explained the planning process.  It is Tom’s hope to keep the meeting time regarding long range planning to 3 hours on Sunday.  Tom encouraged everyone to keep the comments coming regarding the questions posed to the Board by President Tomlinson pertaining to the long-range plan for AERC.  Questions from the Board regarding AERC’s long range planning process can be posed to Tom via email or telephone call.
A question was raised regarding the recent death of an equine at a ride in the Southwest Region and Jim Baldwin, Chair of the Veterinary Committee, was requested to contact the owner of the equine and discuss necropsy.


Meeting adjourned at 6:36 p.m.


Respectfully submitted,


Kathleen A. Henkel, Secretary Pro Tem

Committee Reports

Education Committee Summary Report March ‘04 – March ‘05

Prepared by Co-chair Stagg Newman


During the last year the AERC Education Committee continued to expand its education of the AERC members through:

·         print media via Endurance News and direct mailing,

·         through  electronic means via the AERC web page and via co-sponsoring with the Ride Mangers Committee and the Vet Committee the vet video

·         through in person contacts via clinics and by encouragement of mentorships.  We also published guidelines for choosing mentors in EN.

We also published in Endurance News the long terms educational objectives and goals for AERC which were incorporated into the Past President’s recommendations that were presented at the 2004 March Sunday Board meeting.

I.  Print media

·         A member of the EC published an EN column in every issue of EN.  This year we had articles from most of the members of the EC.  At the suggestion of members we had numerous articles addressed to experienced riders wishing to improve their horses’ performance in addition to articles on horse welfare and safety.

·         Directly worked with authors who were not members of the EC to publish at least another dozen educational articles which originated either because we solicited them or members contacted the Education Committee

·         Reviewed all articles of an educational nature that were submitted directly to the office

·         Send a direct mailing to  all AERC members entitled “Three Keys to Safe Competition

·         Published in EN the long term education objectives and goals for AERC which had been incorporated into the Past President’s recommendations at the 2004 March Board meeting.


II.  Electronic Media

·         Continued to update  the AERC Education Page on the AERC web site

·         Added new material for clinics that can be downloaded and used by AERC members who are conducting their own clinics.

III.  Clinics

·         Ann Cofield developed material for and then conducted a one-day clinic for endurance riders.  The material from that clinic is now posted on the AERC web site for use by all AERC members.  Ann wrote an article for EN entitled “You can do, we can help” to make members aware of the material and to encourage others to give clinces.

·         Stagg Newman  developed a clinic on how to prepare for and ride 100 mile rides and gave this clinic at several rides this year.  The ideas from this clinic were incorporated into EN columns and the outline is available for use by others.

The AERC Education Committee  is now working on two new proposals for consideration in the future:

·         A nominal scholarship award for junior riders achieving certain milage objectives towards college education.  Details of the proposal, funding requirements, funding source, etc. are still being developed.

·         An on-line educational  class on the physiology, care, and feeding of endurance horses.  The course would be offered through the University of Guelph, which already has similar course in equine physiology, etc. under the leadership of Dr. Gayle Ecker.  The course would draw on current materials that would be focused on the endurance horse as well as experts in the endurance horse (vet, riders, nutrionists, …_)  This exciting proposal is in the early stage of formulation.

Research Grants

Prepared by Bob Morris, Chair



The AERC Research Grants Committee currently has in place three signed contracts for research to be funded by the American Endurance Ride Conference. These grants have been made to the New Bolton Center, Michigan State University and the University of Wisconsin.


The projects being conducted by the New Bolton Center and Michigan State have been in progress for one ride season and the research teams have acquired their initial data and will be working on it during the winter months. No reimbursement has yet been made on these contracts and the allocated monies are in reserve accounts awaiting deliverables.


The third grant approved by the AERC Board of Directors was just consummated in a signed contract with the University of Wisconsin. This project will get underway in the proximate months and continue for an additional season.


A fourth grant from Va. Tech at Middleburg is currently under consideration for approval.


Information from the Research being conducted by Michigan State University is being considered for inclusion in our web pages. It is also the intent of the researchers from the University of Wisconsin to be linked to our AERC web system for the benefit of the Membership.


The Research Grants Committee will continue to prospect for research projects that will be of benefit to the membership of the AERC, as funds allow.


The following page provides a short spreadsheet illustrating the full financial status of the Research Grants Committee allocated funds.






















Michigan State University




New Bolton Center








University of Wisconsin




Va. Tech Middleburg
























Funds currently available





































The above table relates to the current financial status of the AERC Research Grants. In the fiscal year 2004 the Board approved grants to the New Bolton Center and to Michigan State University in the aggregate amount of $23,050. The initial seed allocation to the AERC Research Grants Committee was in the amount of $45,000, leaving an uncommitted balance of $21,950.


So far in the fiscal year of 2005, the AERC Board has approved grants totaling $21,528 issued to the University of Wisconsin, leaving a current balance of $422. We currently have up for approval in 2005, an additional proposed grant for Va. Tech at Middleburg amounting to $16,500.


Action on the Middleburg grant has not been expedited to allow the acquisition of additional information about related research and also to the fact that available monies for 2005 have not been determined. Should the grant request be approved by the AERC Board of Directors it will not be consummated until funds are made available.



**Middleburg Ag Proposal: 


Do risks of potassium supplementation depend on speed?

Research Proposal, January 2005 (updated)

T.M.Hess, DVM, MS, PhD

Pratt Fellow in Equine Nutrition, Virginia Tech


Fatigue and neuromuscular hyperexcitability are associated with high concentrations of potassium in extracellular fluid and blood plasma (1,2).  They contribute to poor performance and elimination from endurance races. A critical review of 7 studies suggested a threshold of 4 m/sec (9 mph) on the flat for an increase in plasma potassium3.  It was proposed that endurance horses should be provided with potassium-free electrolyte supplements when speeds of > 4 m/sec had been achieved or were expected, and with potassium-rich mixtures for slower speeds and immediately after the event.  In general, increase in plasma potassium is proportional to exercise intensity. 4, 5

Neuromuscular hyperexcitability develops when the negative resting membrane potential becomes more positive and approaches an activation threshold when then membrane discharges.  During this phase likely clinical manifestations are heart rate arrythmias, increased gut motility, thumps, muscle twitches and fasciculations.  Further positive change passes the threshold and the muscle becomes unresponsive, gut motility ceases and skeletal muscles fatigue is seen as a reluctance or inability to move.

Our first comparison of free- and rich-potassium mixtures in a 50-mile race indicated that neuromuscular excitability reached a statistically risk zone in 1 of 171 horses given potassium-rich mixtures but only 1 in 769 in those receiving potassium-free supplementation. 2  In a treadmill experiment simulating a 50-mile ride, correspond estimates were 1 in 4 horses and 1 in 18 horses reaching the risk zone.6  In contrast, in our second actual race, conditions were hotter and more hilly, horses ran consistently slower than 4 m/sec, plasma potassium declined (instead of rising) and contraindicated the use of potassium-free mixtures.7 Thus at present we suggest that the rider has decision to make depending on the horse’s recent and expected intensity of effort.

One weakness in this series of studies has been the failure to observe clinical signs of neuromuscular excitability.  The most likely would be heart arrhythmias that could be detected objectively by electrocardiography.




Neuromuscular hyperexcitability is manifested during endurance races as heart rate arrythmias, muscle twitches and fasciculations, irregular gut motility and a lower performance.  The resting membrane potential is determined mainly by the distribution of potassium ions across the muscle membrane.  The concentration of potassium inside the cell is much higher (about 124 mEq/L) than the concentration outside the cell (about 4 mEq/L).  During exercise at speeds greater than 4 m/s (9 mph) on the flat plasma potassium concentration will increase despite sweat losses.  Increases in plasma potassium will change he ratio of extra-cellular: to intra-cellular potassium increasing the resting membrane potential, increasing neuromuscular excitability.

Threshold potential is the level of depolarization any stimulation has to reach in order to initiate a muscle contraction.  The resting potential is about 15 mV below the threshold potential.  The calcium ions are the main responsible for the threshold potential.  During endurance races low plasma calcium is commonly seen.  It decreases the threshold potential and increases neuromuscular excitability because the threshold potential gets closer to the resting membrane potential.  Low plasma calcium is caused by metabolic alkalosis, which is also a common finding during endurance races.  Certain diets rich in potassium and or sodium have a high cation-anion difference (i.e. high pasture and hay).  These diets can lead to chronic alkalosis.  When an endurance horse exercises, alkalosis will be exacerbated under these diets and with electrolytes rich in potassium and sodium. Electrolytes rich in sodium and chloride help to reduce cation-anion difference and attenuate alkalosis, mainly chloride supplements.  Clinical signs associated with low calcium are heart rate arrythmias, thumps, and abnormal gut motility.  The combination of high plasma potassium and low plasma calcium may exacerbate clinical signs associated with neuromuscular hyperexcitability.



Research Results

                Plasma potassium concentrations increased during the first Middleburg Research Ride at average speeds of 3.3 m/s (7.4 mph) over hilly terrain.  Plasma pH increased at the first vet check (horses became alkalotic) and decreased at 50 miles and recovery (horses became acidotic).  Supplementation with potassium-free, sodium rich electrolytes attenuated acidosis at the end of the ride. Lower plasma potassium was found in the potassium-free supplied horses at 80 km, which may lead to less neuromuscular hyperexcitability. 

                During the second Middleburg Research Ride results confirmed that potassium supplementation affects plasma potassium concentrations. Lower plasma potassium concentrations were seen in potassium-free supplied horses.  However, average speed was only 2.8 m/s (6.3 mph) over hilly terrain and increases in plasma potassium concentrations were not seen.   Horses supplied with two experimental feeds had higher calcium concentrations than horses supplied with commercial feeds.  Horses supplied with potassium–free electrolyte formulas also had higher calcium concentrations than horses supplied with potassium rich electrolyte formulas.  Horses on the experimental feeds also were less alkalotic than horses on commercial feeds, leading to the higher calcium concentrations.  Three eliminated horses had heart rate arrythmias and a labile heart rate.  These horses had higher plasma potassium and lower plasma calcium levels compared to finishers.

                The third experiment was 50-mile simulated endurance ride on the treadmill.  The experiment confirmed that potassium supplementation affects plasma potassium concentrations.  Horses on potassium-rich electrolytes had higher potassium plasma concentrations during exercise and had a much greater chance to have clinical signs associated with increased neuromuscular excitability.  Resting electrocardiograms were done and no differences were seen between the two electrolyte supplemented groups.

                The fourth experiment was a treadmill experiment with horses exercising at higher speeds (13.4, 15.7 and 18 mph) for shorter distances.  At these speeds plasma potassium concentrations are higher and horses are more likely to reach plasma potassium levels that will increase neuromuscular hyperexcitability.  Horses supplied with potassium rich formulas had higher plasma potassium concentrations, and were at much higher risk to have clinical signs associated with neuromuscular hyperexcitability.  Horses supplied with potassium-free electrolyte formulas had higher plasma calcium concentrations than horses supplied with potassium rich formulas.  Also horses supplied with potassium rich formulas had higher plasma lactate, indicating more anaerobic metabolism and could indicate more fatigue.


                In summary, the experiments clearly demonstrated that supplementation of potassium-free electrolytes will lead to lower plasma potassium concentrations during exercise.  Higher plasma calcium concentrations were also found in potassium-free supplemented horses.  Lower plasma potassium and higher plasma calcium concentrations will reduce the risk of clinical signs related to increased neuromuscular hyperexcitability. 


The general objective is to improve the care and performance of the endurance horse by administration of water and electrolytes during, after and, perhaps, before an event.

Specific objectives are to compare the effects of potassium-free and potassium–rich mixtures on (a) plasma concentrations of potassium ions and heart arrhythmias (palpitations, monitored by electrocardiography), and (b) plasma concentrations of potassium ions hydrogen ions (acidity), especially in relation to a fatigue, and possibly a new form of reluctance to move (‘tying-up’). 

To increase the likelihood of observing heart changes and fatigue, we will run horses at higher speeds on the treadmill than we have previously.  

Experimental design and protocol: 

The effects of two electrolyte replacement formulas, one potassium-rich  (EM+K) and one potassium-free (EM-K) will be tested during an exercise test on the treadmill. 



Thirteen horses Arabian and Arabian cross-bred will be trained for 20 weeks prior to the test. 


Electrolyte composition

K free formulas will contain 21.8 g of sodium chloride, 1.7 g of calcium chloride, 1.1 g of magnesium chloride, and 0.13 g of monosodium monophosphate per dose.  Potassium-rich formula will contain 21.8 g of sodium chloride, 1.7 g of calcium chloride, 1.1 g of magnesium chloride, 13.31 g of K acetate and 0.13 g of monosodium monophosphate per dose.

Two doses will be supplied one hour prior to exercise start, and 2 more doses at 19 minutes of every rest stop, as well as after finishing the test.


Exercise test  

Thirteen horses will be submitted to three exercise bouts of 7 miles at an exercise intensity of 4, 5, and 6 m/s at 3o incline (6%).  At every bout start horses will be warmed up for 5 minutes at 1.8 m/s on a flat TM before being submitted to the 4, 5, and 6 m/s intensity exercise. Horses will be cooled down for 5 minutes at the end of each loop walking at 1.8 m/s.  Rest stops (R1, R2) of 20 minutes will be provided at the end of each bout where electrolytes will be administered orally at 19 minutes of the resting period and water will be available during the 20 minutes of rest.

Two baseline blood samples will be taken in the morning before the first dose of electrolytes is administered. The other samples will be taken five minutes before exercise starts, after 5 minutes of walk, at five minutes of trot (canter) and every 10 minutes during the trot (canter) until the five minute cooling down starts (B11, B12, B13, B14; B21, B22, B33, …, B3NN) and at 0, 5, 10 and 19 minutes of every rest period (R11, R12, R13 R21, …, R23).  At the end of BI and B2, horses will be walked at 1.8 m/s for 5 minutes and a blood sample will be taken 1 and 5 minutes of walking.   After the end of B3 horses will be cooled down (C) walking at 0o incline for 10 minutes and 2 blood samples will be taken every 5 minutes during this period (CD1, CD2).  Recovery will start after the cool down period.  Blood samples for the recovery period will be taken at 0, 5, 10, 15, 20, 25, 30, 40, 50, 60, 90, 120, 180 minutes and in the morning after the test. 

Horses will be acclimated and trained to exercise on the treadmill before the test. The electrolytes will be supplied two hours before, and at 15 minutes of every rest period, as well as 10 minutes after the end of the exercise test.  The horses will be weighed before, at the end of every bout and at 19 minutes of every rest period, at 30, 60, 180 minutes after, and the morning after the test.  During the ET recovery time, the horses will be allowed to have access to water and hay.

EKGs will be monitored during the exercise phase with a digital Holter recorder.  Data will be sent to Penn State for analysis.  Any abnormalities in the EKG s will be assessed.


Dependent variables:

Blood will be collected from catheterized jugular veins into blood gas syringes will be analyzed on the Nova Blood gas machine for the determination of: hematocrit and hemoglobin; glu, lac, pH, Na, K, Cl, Mg, PCO2, PO2, BUN.  Blood from the heparinized tubes will be centrifuged at 3000G for 10 min and analyzed for PO4, TP and alb.


                            Statistical Analysis:

             ANOVA repeated measures in a mixed model for the blood and plasma samples comparing the effects of the two electrolyte mixtures.               

Likely outcomes

               Plasma concentrations of potassium and hydrogen ions will be less elevated at high speeds in horses give potassium-free electrolytes mixtures, thereby reducing the risks of heart disturbances and muscle fatigue.


1. Allen D and Westerblad H  Lactic acid- The latest performance-enhancing drug.  Science 2004; 305:1112-1113.


2. Hess TM, Kronfeld DS, Williams CA et al. Potassium supplementation affects acid-base status and plasma ion concentrations of horses during endurance exercise.  Am J Vet Res, accepted for publication.                                                                         


3. Kronfeld, D.S. 2001. Body fluids and exercise: replacement strategies. J Equine Vet Sci 21:368-375.


4. Harris, P.; Snow, D.H. 1992. Plasma potassuim and lactate concentration in Throughbred horses during exercise of varying intensity. Equine Vet. J., 23:220-224.

5. Gottlieb-Vedi, M., K.Dahlborn, A.Jansson, and R.Wroblenski. 1996.  Elemental composition of muscle at rest and potassium levels in muscle, plasma and sweat of horses exercising at 20oC and 35oC. Equine Vet. J. Suppl. 22:35-41.


6. Hess,T.M., K. Treiber, D.S. Kronfeld , J.E. Waldron, C.A.Williams, M. S. Freire, A.M.G. Braga , L.S. Gay , and P.A. Harris. Potassium supplementation affects plasma [K+] during a simulated 80-km endurance test on the treadmill. J Anim Sci 2004; 82 (suppl. 1):97.


7. Hess, T.M., K. Greiwe-Cradell, D.S Kronfeld, J.E. Waldron, C.A. Williams, M.A. Lopes, R.M. Hoffman, L.A.Gay, D. Ward, and P.A. Harris.  Potassium-free electrolytes and calcium supplementation in an endurance race.  Proceedings of the Eighteenth Equine Nutrition and Physiology Symposium, East Lansing, MI, June4-7, 2003, 18:148-149.


Blood gas analyzer reagents                                         $ 6000.00


Beckman analyzer reagents                                         $ 3000.00


Syringes, blood tubes                                              $ 700.00


Computer services, statistical consulting                                   $ 800.00


Holter recorder, 3 units                                               $ 6000.00


TOTAL                                                                          $ 16500.00