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Chris M. Gregory, PT, PhD, Research Assistant Professor University of Florida, Carolynn Patten, PT, PhD
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drewgreg{at}phhp.ufl.edu Chris M. Gregory, PT, PhD, et al.
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In the December, 2007 issue of PTJ, Sullivan and colleagues1 present the results of their single-blind trial that studied walking outcomes in participants poststroke who were randomized into 1 of 4 paired exercise intervention groups: (1) body-weight–supported treadmill training (BWSTT) combined with upper-extremity ergometry (BWSTT/UE-EX), (2) BWSTT and recumbent cycle ergometry (BWSTT/CYCLE), (3) BWSTT and lower-extremity resistance exercise (BWSTT/LE-EX), and (4) a “sham,” or control, group that performed the CYCLE exercise plus the UE-EX exercise (CYCLE/UE-EX). The authors’ overriding conclusion was that BWSTT is more effective in improving walking outcomes compared with interventions that did not include the walking intervention. The authors extend their conclusion to state that, “consistent with the overtraining literature, [lower-extremity] LE strength training alternated daily with BWSTT did not provide an added benefit to walking outcomes.”1(p1580) This conclusion was motivated by their results, which failed to reveal statistical differences in walking outcomes between the BWSTT/LE-EX group and the other 2 treadmill walking groups. Their findings are interpreted primarily as an overtraining effect that potentially interfered with the functional gains expected in this group. Although this trial seemingly demonstrates a consistent effect of BWSTT when combined with other activity-based strategies, there are several key issues to recognize when interpreting the data presented in this article, especially as they relate to the BWSTT/LE-EX group. Of note, Carey,2 in an invited commentary, made a number of astute observations related to the findings of this study—namely, the potential for endogenous neural growth factors to contribute to the gains seen in the BWSTT/UE-EX exercise group. Accordingly, we will focus our discussion on the data related to participants who performed resistance exercises. At first glance the interpretation of the data presented seems appropriate. Given that the BWSTT/LE-EX group did not show additional improvements in walking outcomes suggests that the authors’ a priori hypothesis—that this group would show further benefit—should be rejected. To support their interpretation, the authors refer to studies of older individuals who are not disabled to suggest an “overtraining” effect may have occurred.3,4 However, a critical detail in the results presented by Sullivan et al1 contrasts with those from the studies used to support their notion of overtraining. The BWSTT/LE-EX participants did not produce significant strength gains in any of the 4 composite measures reported. This detail should be carefully considered when interpreting the results of the study by Sullivan et al. The apparent goal of resistance exercise delivered in the present study design was to increase muscular strength. However, no changes in strength were produced. Therefore, a more appropriate conclusion by these authors would be that the resistive exercise as delivered in this protocol (eg, mode, duration and intensity) was not effective at producing either gains in strength or any added benefit in walking outcomes. Their conclusions that resistance training did not provide an added benefit to BWSTT superficially suggest that increased strength did not augment the effects of BWSTT. However, this is not what their data reveal. Indeed, the lower-extremity “strengthening” exercise program failed to produce strength gains. Thus, to explain these findings we must subscribe to 1 of 3 potential explanations: (1) it is not possible to induce significant strength gains via resistance training in persons poststroke, (2) the intervention delivered in this study represented an insufficient stimulus to elicit gains in strength in the study sample, or (3) the combined training did indeed interfere with gains in strength, consistent with what some refer to as overtraining. The issue of whether people poststroke can be strengthened has been addressed in a number of studies. To date, the data from these studies have consistently demonstrated significant gains in strength following resistance training intervention. In fact, Sullivan and colleagues present a nice summary of a number of studies showing that strengthening is possible in this population5-10 and strength gains are often accompanied by functional improvements.5,11-13 Thus, it is unlikely that the lack of increase in strength following LE-EX reflects an inability on that part of subjects with hemiparesis to increase strength following resistance training. The second possible explanation for the lack of improvement in strength following LE-EX may be the design of the resistance training intervention. Two obvious factors contrast between the intervention delivered by Sullivan et al and those in previous studies that have examined concomitant resistance and endurance training: (1) the type of exercise equipment used to deliver the resistance intervention and (2) the training intensity. The authors report their subjects performed resistive exercise “with loading provided by equipment typically present in the clinic such as elastic bands of varying resistance and cuff weights, and included muscle-specific exercises that clinicians use with their patients.”1(p1582) In addition, given that many of the participants were not able to perform given joint actions out of synergy (as determined during Fugl-Myer assessments), positional changes were also used to provide resistance as well as indicate progression. Although we recognize the apparent clinical relevance of this design and applaud the authors for their attempt to deliver the most clinically relevant protocol, it seems unlikely that they were able to accurately quantify the relative loads reported in the protocol (ie, 80% of a 10-repetition maximum [10-RM]) using resistive tubing or positional changes. Specifically, it is important to question how a true 10-RM can be determined and, subsequently, how an 80% relative intensity can be determined using noncalibrated metrics such as elastic tubing or body position? To compound the potential difficulty in accurately quantifying loads, it is not clear whether or how the therapeutic intensity was progressed over the course of treatment. Although Sullivan et al reported that “a progression algorithm was used to increase workload throughout the 12 treatment sessions,”1(p1586) little detail is provided that would inform the reader how to replicate their intervention. The clear absence of any indication of improved strength strongly suggests that the LE-EX resistance training intervention involved an insufficient stimulus to induce therapeutic adaptations, either strength gains or improvements in locomotor function. In their introduction, Sullivan and colleagues suggest that “muscle strength training may lead to improvement in both lower-limb strength and gait speed, although controlled studies that isolate this intervention are lacking.”1(p1581) In addition, when reviewing previous studies these authors suggest, “because the protocols were multifaceted, it is not possible to determine the precise role that the strength training component may have played in improving walking function.”1(p1581) We contend that the present study did not address either of these proposed deficiencies in the literature or the potential confusion resulting from studies that included multifaceted intervention strategies. To conclude either that LE-EX did not augment BWSTT or that LE-EX presented an interference, or overtraining, effect requires examination of the efficacy of the intervention at improving strength. This question could have been addressed by Sullivan et al with the addition of a group that performed only LE-EX but did not participate in BWSTT. If the independent effects of LE-EX included significant improvements in strength, whereas the combined effects showed no gains, the authors would have better justified their conclusion that there was no additive benefit of strengthening and thereby identifying the intriguing potential that low-to-moderate intensity LE-EX performed on alternate days created an overtraining effect. Given that these data are not available, we can only speculate regarding whether these or other differences in program design explain the lack of response to LE-EX reported in this article. Again, a more appropriate interpretation of these data would be that the resistive exercise as delivered in this protocol was not effective at producing either gains in strength or any added benefit in walking outcomes. In summary, proof of concept in any resistance training intervention requires documentation of increases in strength. Given that no changes in strength were observed following BWSTT/LE-EX begs us to question why. Although the potential for overtraining does indeed exist in this group, sufficient data to justify this conclusion in the study by Sullivan et al are not presented. As previously mentioned, if the positive effects of the LE-EX protocol were demonstrated independently of BWSTT and, furthermore, shown to significantly improve strength, the explanation provided by Sullivan et al would be better justified. Given the data available, many questions remain regarding the benefit of adding resistance training as an adjunct to BWSTT to augment walking outcomes. References 1 Sullivan KJ, Brown DA, Klassen T, et al; for the Physical Therapy Clinical Research Network (PTClinResNet). Effects of task-specific locomotor and strength training in adults who were ambulatory after stroke: results of the STEPS randomized clinical trial. Phys Ther. 2007;87:1580-1602. 2 Carey JR. Invited commentary on "Effects of task-specific locomotor and strength training in adults who were ambulatory after stroke: results of the STEPS randomized clinical trial." Phys Ther. 2007;87:1603-1605. 3 Wood RH, Reyes R, Welsch MA, et al. Concurrent cardiovascular and resistance training in healthy older adults. Med Sci Sports Exerc. 2001;33:1751-1758. 4 Delecluse C, Colman V, Roelants M, et al. Exercise programs for older men: mode and intensity to induce the highest possible health-related benefits. Prev Med. 2004;39:823-833. 5 Teixeira-Salmela LF, Olney SJ, Nadeau S, Brouwer BJ. Muscle strengthening and physical conditioning to reduce impairment and disability in chronic stroke survivors. Arch Phys Med Rehabil. 1999;80:1211-1218. 6 Teixeira-Salmela LF, Nadeau S, Mcbride I, Olney SJ. Effects of muscle strengthening and physical conditioning training on temporal, kinematic and kinetic variables during gait in chronic stroke survivors. J Rehabil Med. 2001;33:53-60. 7 Sharp SA, Brouwer BJ. Isokinetic strength training of the hemiparetic knee: effects on function and spasticity. Arch Phys Med Rehabil. 1997;78:1231-1236. 8 Dean CM, Richards CL, Malouin F. Task-related circuit training improves performance of locomotor tasks in chronic stroke: a randomized, controlled pilot trial. Arch Phys Med Rehabil. 2000;81:409-417. 9 Weiss A, Susuki T, Bean J, Fielding RA. High intensity strength training improves strength and functional performance after stroke. Am J Phys Med Rehabil. 2000;79:369-376. 10 Ouellette MM, LeBrasseur NK, Bean JF, et al. High-intensity resistance training improves muscle strength, self-reported function and disability in long-term stroke survivors. Stroke. 2004;35:1404-1409. 11 Patten C, Dozono J, Jonkers I. Gait speed improves following dynamic high-intensity resistance training in persons post-stroke [abstract]. Stroke. 2007;38:465-466. 12 Yang YR, Wang RY, Lin KH, et al. Task-oriented progressive resistance strength training improves muscle strength and functional performance in individuals with stroke. Clin Rehabil. 2006;20:860–870. 13 Salbach NM, Mayo NE, Wood-Dauphinée S, et al. A task-orientated intervention enhances walking distance and speed in the first year post stroke: a randomized controlled trial. Clin Rehabil. 2004;18:509–519. |
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