Diastolische Funktion bei Athleten
ÜBERSICHT
EXERCISE TRAINING

Exercise Training for Performance and Health

Körperliches Training für Leistungsfähigkeit und Gesundheit

ZUSAMMENFASSUNG

Körperliches Training fördert die Gesundheit und körperliche Leistungsfähigkeit. Eine große Ansammlung wissenschaftlicher Literatur belegt die positiven Effekte körperlicher Aktivität in einer semiquantitativen Art und Weise. In diesem Artikel werden aktuelle Studien zur Trainingsdosis mit normalen Individuen (Schritte pro Tag) und Athleten (Volumen und Intensität von Trainingsläufen in Vorbereitung auf Marathonläufe) präsentiert. Zusätzlich werden auch Studien vorgestellt, die mittels der RPE Methode und dem ‚talk test‘ Trainingsintensitätsbelastungen von Athleten sowie gut trainierten Breitensportlern überwachen. Abschließend werden Daten zu ‚Pacing‘ Strategien mit Herzpatienten aus neueren Studien vorgestellt. Die zusammengefassten Daten in dieser Übersicht sollen dazu dienen eine kompetente Beratung zur Trainingsgestaltung für jedes Fitnesslevel zu ermöglichen, mit der Absicht individuell gesetzte Ziele bezogen auf körperliche Leistung und Gesundheit zu erreichen.

Schlüsselwörter: Training, Gesundheit, Sport, Verordnung.

SUMMARY

Exercise  training  is  an  important  positive  activity  for  both  health  and  performance.  A  rich  literature  demonstrates,  in  a  semi-quantitative  way,  the  value  of exercise. However, knowledge about how to improve the process of giving exercise advice is always important. This paper reviews recent studies relative to exercise dosimetry in both normal individuals (steps per day) and athletes (the volume and character of training runs in preparation for marathon races). It also provides data regarding the use of the Session RPE (rated perceived exertion) method and the Talk Test to monitor training load and control training intensity in well-trained individuals and athletes, respectively. Lastly, evidence extending recent findings on pacing strategy into a new population (patients with cardiovascular disease) is presented. In total, the new data presented in this manuscript add information that  may  be  useful  in  refining  the  process  of  advising  exercisers  at  all  levels  on better ways to achieve their exercise goals.

Key Words: Training, health, sport, prescription.

PROBLEMS AND OBJECTIVES

Exercise is one of the most unequivocally positive things that humans can do. Whether training for athletic performance or for a healthy lifestyle, the value of increasing levels of exercise can hardly be  overstated  (4, 5, 11).  The  beneficial  adaptations  to  exercise  are based primarily on the ability to cause gene expression and protein synthesis that contribute, in a mode specific way, to both performance and health. Although there are a variety of reports (5, 15, 28), and professional society guidelines (19) about the quantity, quality and pattern of exercise training necessary to achieve the goals of exercise training, there is always the need to further refine the prescription of training programs. For example, guidelines that recommend  30  minutes  of  moderate  intensity  exercise,  performed on most days of the week (19) are similar to recommendations of 10,000 (or even more) steps per day (2,30), although the agreement between the methods is not entirely clear. At the other end of the continuum, information about how to prepare for athletic challenges (e.g. marathon running) have recommendations about the total volume of training and the value of specific (e.g. long runs) training, but little quantitative evidence related to the outcomes of training (9, 18, 29).  Similarly,  although  there  are  established  guidelines  regarding prescription of exercise based on relative heart rate (e.g. % heart rate reserve) or metabolic intensity (e.g. %VO2 reserve), these recommendations universally suffer from the limitations of the ‘relative percent concept’ (22, 26) (e.g a particular relative percent of %VO2 reserve is not equivalently demanding in different individuals). It has been recognized for more than a generation that training prescription based blood lactate or ventilatory responses to training is inherently superior to relative percent methods (2, 20, 23, 24, 27). However,  the  technical  requirements  for  such  prescription  have prevented its’ wide use. Recent studies of the Talk Test (a surrogate of ventilatory and lactate threshold) (8, 13, 25, 31) and of the ability of the Talk Test to ‘translate’ exercise testing results to absolute exercise intensity (17, 21) suggest the applicability of this very simple technology. Lastly, recent interest of pacing strategy in athletes (16)  and  the  association  between  unaccustomed  heavy  exercise and  medical  complications  related  to  exercise  (14),  suggest  that information  about  pacing  needs  to  be  extended  to  non-athletic populations.  Thus,  despite  the  very  good  knowledge  about  how to prescribe exercise for performance and health, there is always a need to improve upon the ‘state of the art’. Indeed, beyond the limitations of the ‘relative percent concept’ already discussed, the range of relative percents recommended in professional guidelines (19) is so broad as to be of little practical help during the process of exercise prescription. This paper is designed to discuss recent data from our laboratory which addresses these issues.

MATERIAL AND METHODS

The presented data are the product of five previously unpublished investigations into monitoring the volume and intensity of exercise and the pattern of energy use during exercise training. All studies were approved by the local ethics committee and all subjects provided written informed consent.
In  order  to  compare  ‘time  structured’  versus  ‘steps  per  day structured’ related exercise, Study 1 was performed by measuring of the daily time that structured exercise was performed versus the total ‘steps per day’ accumulated (including both normal activities and structured exercise). Subjects, ranging from healthy university personnel to clinically stable cardiac patients (8 males age 51±12y, 12 females, age 44±15y) recorded their steps per day on an electronic pedometer and the number of minutes of structured exercise each  day  for  two  consecutive  weeks.  The  first  week  included  the normal level of exercise performed by the subjects. In the second week the subjects were asked to increase the amount of walking as much as possible. The average steps • d-1 and minutes of structured exercise • d-1 was recorded over the entire week in order to prevent any one atypical day from overly influencing the results. The intrinsic  logic  of  this  study  was  that  by  comparing  structured  exercise time to steps taken per day, that these two methods of recommending exercise could be unified. Obviously, non-ambulatory exercise cannot be evaluated in terms of steps per day, but the translational logic to minutes per day is assumed to be valid.
Study  2  surveyed  training  and  performance  information  of ~500 marathon runners during several marathon races, all contested in good environmental circumstances. The subjects represented a wide range of age (20- 66 years) and abilities (2:24- 5:10), 60% were male. Information about training volume and number of long (>32km)  runs  in  the  8weeks  preceding  each  race,  together  with race  performance,  including  the  slowdown  during  the  last  10km were  gathered  using  questionnaires,  and  analyzed  relative  to  the performance of groups of runners with varying performance. The groups were formed from natural divisions of performance times. Some of these data were published many years ago in the non-peer reviewed literature (9), although the current analysis is unique.
To extend our understanding of the validity of the Session Rating of Perceived Exertion (RPE) method (10, 12), Study 3 compared session RPE (a global rating of overall perceived exercise intensity, gathered 30 min following the conclusion of exercise (10)) with the average  RPE  (measured  every  10  min)  achieved  during  a  60- min exercise  bout  in  very  well-trained  non  athletes  (6males,  22±3y, VO2max=55±4; 6females, 20+1y, VO2max=47±5).
In Study 4 we observed heart rate, blood lactate, RPE and the speech  comfort  (17, 21)  during  bouts  of  steady  state  exercise  in competitive  runners  (9males,  22±10y,  VO2max=67±9;  5females, 29±9y,  VO2max=51±3).  Each  subject  performed  an  incremental exercise test, with measurement of the Talk Test (17, 21) to define exercise intensities relative to the ability to speak comfortably. The Talk Test is performed during incremental exercise, by having the subjects recite, aloud, a standard 31 word paragraph at the end of each 2 min exercise stage. The subject is then asked “can you speak comfortably?” Only 3 answers are allowed: “yes”, wich we refer to as a Positive Talk Test; “yes, but……”, which we refer to as an Equivocal Talk Test; and “no”, which we refer to as a Negative Talk Test. Subsequent, steady state exercise bouts were performed at intensities associated with the Equivocal stage, the Last Positive stage, or the stage before the Last Positive stage (LP-1) of the Talk Test during incremental exercise.



Lastly,  in  order  to  gain  a  better  appreciation  of  how  cardiac patients learned to pace their exercise intensity, a critical issue in terms of the safety of exercise, we observed a group of patients in a cardiac rehabilitation program (6males, 63±13y; 6females, 61±6y) during four performances of the 6- minute walk test. This test is a widely  popular  sub-maximal  exercise  test,  used  for  both  training and outcome evaluation (1). The walks were separated by ~1 week, and  the  patients  were  instructed  to  walk  at  the  fastest  pace  at which  they  were  comfortable.  Pace  was  measured  over  each  30s of the 6min test.

RESULTS

Study 1: There was a significant increase in the number of total and structured  steps  during  the  week  when  we  asked  the  subjects  to walk as much as possible (Tab. 1), associated with an increase in the minutes of structured exercise. The number of steps not associated with structured exercise remained unchanged. The number of  steps  in  the  second  week  approximated  the  amount  observed by  Bassett  et  al.  (2)  in  Amish  farmers, living a lifestyle similar to 19th century agriculturalists. The overall  relationship  between  the time of structured exercise in relation to the steps per day is presented in Figure 1. There are several obvious relationships evident in  the  data,  including  the  close approximation of 30min of structured exercise vs 10,000 steps per day  (30),  70min  vs  15,000  steps per day (2) and 120min vs 20,000 steps per day, which may approximate  estimates  of  the  exercise  load  undertaken  by  hunter gatherers (7) (Fig. 1).
Study  2:  Observations  of subgroups  revealed  that  faster marathon runners are faster both because of a faster early running pace  and  because  of  a  less  pronounced  slowdown  during  the last 10km (Figure 2). It is also evident  that  faster  runners  (<3hr) run  at  approximately  their  normal  training  pace  in  both  the early  ( first  15km)  and  late  (last 10km)  race  segments.  However, the  slower  runners  run  much faster  than  their  training  pace during the first 15km of the race, and much slower during the last 10km of the race, suggesting that in addition to being inadequately  prepared  generally  they  may also be making a pacing mistake. The normalized slowdown (pace in  last  10km- pace  in  the  first 15km), evaluated in terms of training volume (with 800km in the 8weeks  preceding  the  race  used as  a  reference  (9, 18, 29)  shows that low training volume runners have  slowdowns  proportional  to their lack of appropriate training volume. This is also evident when slowdown is evaluated relative to the number of long (>30km) runs or the product of training volume and long runs (Fig. 2).
Study 3: The response of RPE during 60min bouts at the intensity  associated  (during  incremental  exercise)  with  the  Equivocal, Last Positive, and the stage before the last positive stage (LP-1) of the Talk Test are presented in Figure 3, together with the relationship between the average RPE during the bout and the Session RPE. There was the expected ‘drift’ of RPE during the course of the exercise bouts, which was more evident at higher exercise intensities. In general, the LP-1 stage during incremental exercise was the highest workload associated with stable exercise responses during 60min of sustained exercise, which agrees with our earlier findings in welltrained non-athletes (21). However, these well-well trained subjects seem to be able to tolerate sustained exercise at a higher intensity (relative to incremental exercise Talk Test responses) than sedentary individuals (17). With the exception of bouts where the average RPE was very high (>7), there was a good correspondence between mean and Session RPE. In very hard training bouts, the Session RPE was greater than the mean RPE, suggesting that the RPE during the latter part of the bout contributed disproportionately to the Session RPE (Fig. 3).
Study 4: Responses of heart rate, blood lactate, RPE and speech comfort during 30min of exercise in athletes are presented in Figure 4. The subjects demonstrated steady state conditions at the absolute intensity associated with the last positive stage of the Talk Test, but were clearly outside steady state conditions at the intensity associated with the equivocal stage of the Talk Test. The results in this population of athletes are similar to those of Jeans et al. (21) in well trained individuals, but different from the findings of Foster et al. (17) in sedentary individuals (who only reached steady state conditions at the stage before the last positive stage of the Talk Test (LP-1)) (Fig. 4).

Study  5:  The  velocity  pattern  during  repeated  trials  of  the 6-minute walk test in cardiac rehabilitation patients are presented in Figure 5. In concert with our earlier findings of pacing patterns in well-trained non-athletes, there was evidence that the subjects ‘held  back’  during  the  first  trial,  and  particularly  during  the  first half of the first trial. With successive trials, the early pace was progressively faster, and over the last 2 trials resembled the U shaped ( fast  start,  steady  pace  middle,  endspurt)  velocity  curve  often seen  in  athletes  during  competition  (16).  These  data  support  the hypothesis that humans regulate their exercise behavior in a way designed  to  minimize  the  likelihood  of  catastrophic  homeostatic disturbances. Just as athletes avoid a too aggressive early pace, in order to prevent a large decrease in pace midway through the event (a competitive catastrophe), patients regulate their early pace in a way that probably avoids myocardial ischemia, at least with new tasks. With experience that performing a task in a particular way did not cause harm, they appear to be willing to start the task more vigorously. Data on the 6- minute walk test may be limited by the inability to actually walk at faster paces. Future studies will need to focus on criterion activities that are not limited by the mechanics of walking. There also appears to be some ‘microvariation’ in pacing amongst the patients, which has also been observed in athletes in competition (C. Thiel, unpublished observations). Whether this is strategic, or simply a response to short term homeostatic disturbances awaits higher resolution data of walking speed within the 6- min walk test (Fig. 5).


DISCUSSION

The results of these studies expand our understanding of how to better prescribe exercise for both performance and health. Our results support the concept that ~30 min • d-1 of structured exercise (19) is comparable to 10,000 steps • d-1(30), and also suggest that ~70min • d-1 is comparable to the 15,000 steps • d-1 of 19th century agriculturists and 120min • d-1 is comparable to the 20,000 steps. d-1 performed by hunter-gatherers (7). It is also evident that both training volume and the number of specific long-run training sessions combine to determine the performance of marathon runners (9, 18, 27), particularly in less well-trained competitors. Our use of the  Session  RPE  as  a  surrogate  for  the  average  training  intensity during exercise bouts (10, 12) appears to be justified by the results of  these  studies,  although  there  is  apparently  a  variance  during very hard training sessions. The Talk Test, a surrogate of the ventilatory  threshold,  appears  to  be  a  viable  method  for  prescribing exercise in competitive runners, just as has previously been show in less well-trained individuals (17, 21). Lastly, it appears that, just as athletes learn to pace themselves during novel tasks, patients learn pacing during successive repetitions of the 6- minute walk test. This is important since, inappropriate pacing can lead, not to the competitive  failures  that  athletes  experience,  but  to  catastrophic medical emergencies.

In sedentary individuals, and in patients with exertional  ischemia,  there  is  good  evidence  that  unaccustomed heavy exercise and/or exercise above the ischemic threshold can lead to triggering of myocardial infarction or to dysrhythmias (14).We have previously presented evidence that maintaining the ability to  speak  comfortably  keeps  patients  with  cardiovascular  disease below the threshold of exertional ischemia (6). The present results, of a learning strategy during the 6- min walk test suggest that patients should be strongly encouraged to ‘work at their own pace’, as there is good evidence that being ‘hurried’ or ’driven’ by an external pacemaker during exercise can contribute to complications during exercise (14).

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Corresponding Author:
Carl Foster
University of Wisconsin-La Crosse
Department of Exercise and Sport Science
133 Mitchell Hall
La Crosse, WI 54601
USA
E-Mail: cfoster@uwlax.edu