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Abstract
Introduction Resistance training is an important component of rehabilitation due to its ability to increase muscular strength and enhance functional ability. The aim of this study was to assess the effects of two different resistance-training programmes currently used in military rehabilitation.
Method 27 male rehabilitation patients, serving with the Armed Forces and suffering from a range of lower limb musculoskeletal injuries were divided into two matched groups. Group 1 (n=14) performed the Daily Adjusted Progressive Resistance Exercise (DAPRE), whereas Group 2 (n=13) performed the Functional Strength Training (FST). An 8 repetition maximum (8RM) deadlift and countermovement vertical jump (CMVJ) test were used as Functional Assessment Tests (FATs) and as measures of changes in strength and power, respectively. Both were conducted on admission and at discharge.
Results Lower limb strength and power increased significantly in both the DAPRE (p≤0.001/p≤0.001) and the FST (p≤0.001/0.001) groups. There was no significant difference between groups for either strength (p≥0.05) or power (p≥0.05).
Conclusions Short-term resistance training during rehabilitation can lead to gains in strength and power despite differences in programme design. However we conclude that three weeks of resistance training is insufficient duration to see significant differences between different training protocols.
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Introduction
Resistance training is an important component of rehabilitation due to its ability to increase muscular strength and enhance functional ability.1–4 The resistance training component of the military rehabilitation model has traditionally been administered using the Daily Adjusted Progressive Resistance Exercise (DAPRE) protocol. This system was first developed by Knight in 19795 as an easy way of applying progressive overload to a resistance training programme in a rehabilitation setting (Table 1).
DAPRE loading protocol as developed by Knight5
However, there are inherent concerns with the use of the DAPRE protocol as a resistance training method. Evidence shows that resistance training induces neural adaptations, both within the central nervous system (CNS) and peripheral nervous system (PNS).6 ,7 These neural adaptations result in increased maximal strength and rate of force development (RFD) within the trained musculature. It is widely accepted that loads above 70% of 1 Repetition Maximum (1RM) are needed to elicit neural or morphological adaptations in skeletal muscle in response to resistance exercise8–10 When extrapolating from repetition continuum tables it is evident that a 10RM load, as utilised by the DAPRE protocol, corresponds to approximately 70% of 1RM11–14 and therefore is of sufficient intensity to induce improvements in maximal strength. However, the two first sets of the DAPRE loading protocol merely employ a percentage of the 10RM and consequently do not fall within the intensity bracket needed to improve maximal strength. Thus, in effect the DAPRE system only features two main work sets that fall within the required intensity range. Whilst strength increases have been observed with single and double set/low volume resistance training programmes it is widely accepted that a multiple set approach to resistance training results in enhanced physiological adaptations that is, increased strength and muscle mass.14–18 Another possible issue with the use of the DAPRE system is the fact that it is generally used with resistance training machines rather than free weights. Evidence suggests that performing the same movement with free weights (FF) versus fixed-form resistance machines (FX) leads to significantly higher activation of stabiliser muscles19 ,20 Enhanced activation of these is generally considered to be beneficial in patients suffering from musculoskeletal injuries.1 ,2
In an attempt to overcome these problems an alternative resistance training programme, which follows more recent guidelines for resistance programme design1 ,9 ,14 has also been utilised at the Defence Medical Rehabilitation Centre (DMRC). This ‘functional strength training’ (FST) programme (Table 2) is based on the three powerlifts (squat, bench press, deadlift), while the remainder of the training volume is made up of functional exercises which are derivatives of the core lifts (overhead squat, step-up, lunges, Romanian deadlifts, high-pulls). Patients typically perform 3–5 exercises with each exercise comprising four sets of 4–6 repetitions at 80–85% of 1RM. All four sets for each exercise are completed before moving to the next exercise. This programme is repeated three times per week and the training load increased weekly based on the ‘2 for 2’ rule described by Baechle et al.14
Example of a functional strength training session (X denotes as explosively as possible)
The military currently only runs 3-week rehabilitation courses at the DMRC; however there are no current studies investigating the magnitude of improvements seen in such a short timeframe. Furthermore, no previous studies have investigated the effects of DAPRE versus functional resistance training methods on measures of strength and power within a rehabilitation context. Based on the current evidence in the literature we hypothesised that patients in the FST group would exhibit significantly better improvements in strength and power when compared to the DAPRE group. The aim of this study was therefore to assess the effects of two different resistance-training programmes currently used in military rehabilitation.
Method
Patients
Twenty-seven participants were all admitted to the DMRC as part of ongoing rehabilitation for a range of heterogenous lower limb musculoskeletal injuries, including anterior compartment syndrome, anterior knee pain (AKP) and patella/meniscus disorders were divided into two groups. All patients were matched for age, height, weight and gender.
Design
The overall design was considered a service evaluation in which a matched-groups analysis of successive cohorts was utilised. Group 1 performed the DAPRE protocol while Group 2 performed the functional strength training programme (FST). Lower body strength was assessed in both groups at admission and discharge using the 8-RM deadlift. Evidence suggests that the deadlift, due to its muscle recruitment pattern may be an effective closed kinetic chain (CKC) exercise to employ in lower limb rehabilitation.21 Due to the untrained nature of the patients a trap-bar was used for ease of execution. Lower body power was assessed in the same testing sessions using the counter-movement vertical jump (CMVJ). This test has served as the field test of choice in determining lower body power for decades,1 ,9 ,14 and has been validated accordingly.22
Due to the increased training frequency advocated by the DAPRE protocol, participants in this group completed 13 resistance training sessions during their admission period, whereas participants in the FST group only completed 7 resistance training sessions.
Statistics
A one-way analysis of variance (ANOVA) was used to assess changes in response to the two resistance training programmes. Overall gains within groups was analysed with a paired t test. The alpha level was at p≤0.05 for all analyses. All statistical analyses were carried out using SPSS V.16.0 (SPSS Inc. USA).
Results
Anthropometric results for the 27 male rehabilitation patients that participated in this study can be seen in Table 3. Values given were those on admission, prior to commencement of the exercise-based rehabilitation programme.
Anthropometric characteristics of participants (mean values with standard deviation in brackets)
The within-groups results showed that lower limb power (CMVJ score) increased significantly in both the DAPRE (p≤0.01) and the FST (p≤0.001) groups at discharge. The magnitude of improvements in CMJ were higher in the FST group and there was less dispersion in the overall data. Nevertheless, no significant difference was observed between the two programmes in terms of improvements in lower-body power (p≥0.05) (Figure 1).
Increases in Power (CMVJ) in response to the two training protocols. Error bars represent standard error of mean (SEM).
Similarly, lower limb strength (DL score) increased significantly in both the DAPRE (p≤0.001) and the FST (p≤0.001) groups at discharge. The relative magnitude of improvement in the two intervention groups is presented in Figure 2. No significant difference was observed when comparing the effects of the two different resistance training protocols on lower body strength development.
Increases in deadlift strength in response to the two training protocols. Error bars represent standard error of mean (SEM).
Discussion
The results of the present service evaluation indicate that during a 3-week rehabilitation programme the DAPRE and FST resistance training programmes are equally effective at improving measures of lower limb strength and power in a group of patients suffering from a range of lower limb musculoskeletal injuries.. However, use of the FST programme appears to be associated with a lower variability in the training outcome. The DAPRE programme was characterised by a very large variation in the results i.e. responders vs. non-responders, whereas all subjects in the FST showed improvements in muscle strength and power.
Although no significant differences were observed in the present study between the DAPRE and FST resistance training programmes the relative improvements were of a greater magnitude in the FST group. It is possible that these differences could have reached statistical significance with a greater sample size or if the resistance training programme would have been extended beyond the 3-week mark, as evidence suggests that strength and power continue to develop and reach higher magnitudes after 6–10 weeks of continued resistance training.1 ,9 ,10 Thus, the fact that the DMRC currently only runs 3-week rehabilitation courses, due to logistical constraints, may limit the benefits of the resistance training programmes. However, the present study suggests that improvements in lower body strength and power are achievable in as little as three weeks. A large body of evidence suggests that the majority of these short-term improvements are due to neural adaptations,1 ,6 ,7 ,9 ,10 however, emerging evidence does suggest that significant increases in muscle cross-sectional area (CSA) can be observed in as little as 3 weeks.23 Because we did not assess possible muscle hypertrophy through Magnetic Resonance Imaging (MRI) or ultrasound, we cannot rule out that morphological adaptations contributed to the increased muscle strength observed in response to either training programme.
Due to its reliance on compound multi-joint movements coupled with a high-intensity loading protocol, the FST programme was considered more stressful to the neuromuscular, endocrine and immune system than the lower-intensity weight-machine-centred DAPRE programme and thus, was only performed 3 days a week. There is general agreement in the literature that resistance training sessions which are associated with a high overall body stress necessitate a reduced training frequency1 ,9 ,10 ,14 ,18 It is therefore worth noting that due to the increased frequency of the DAPRE programme (13 vs 7 sessions), participants in the DAPRE programme completed a much higher training volume but failed to see a concomitant increase in strength and power when compared to the FST group. It is plausible that the higher training intensity in the FST group off-set the reduced training volume and led to comparable results after a 3-week period. This finding supports previous evidence in the literature which suggests that resistance training with a higher intensity (>70% 1RM) is associated with increased gains in strength and power, even in a rehabilitation context.24–28 Furthermore, the total time spent doing resistance training in the FST group was markedly less than in the DAPRE group (90 min per week versus180 min per week). This suggests that using the former approach to resistance training in a busy rehabilitation programme, such as Headley court, could free up more time for other rehabilitation modalities while achieving at least the same beneficial effects on muscle strength and power.
Although this service evaluation failed to demonstrate the hypothesised superiority of the FST protocol it has been suggested that FX movement patterns, as used in the DAPRE protocol, do not promote the neuromuscular coordination required to enhance natural movement patterns.29–31 Thus, attempting to strengthen the target musculature in isolation with various uni-planar, Open-Kinetic-Chain movements has limited carryover effect to the multi-planar compound movements, which patients will encounter in a work or daily-living scenario.32 ,33 Conversely, correct execution of FF exercises may enhance the development of functional strength and power in a patient population due to significant improvements in neuromuscular coordination.2 ,9 ,14 ,34–36 Thus, with regards to developing functional strength, which will carry over into free-living activities, evidence suggests that FST will be a superior training protocol. Unfortunately, a clear limitation of this current service evaluation was that the effects of the two separate training protocols on functional ablity were not assessed. Although some research indicates that there is a significant correlation between maximal muscle strength and functional ability in certain types of disease37 ,38 and aging,39 it is unclear whether this is also the case in our study population with its heterogenous lower limb injuries. Evidence indicates that muscle power may also be strongly correlated with functional ability,40 however, based on the literature we cannot say if this is also the case in our study population. Thus, future research should strive to include tests of functional ability as part of their outcome measures.
Although potentially less effective at improving functional strength, the use of the DAPRE protocol in conjunction with resistance training machines can possibly be useful in the most deconditioned/de-trained subgroup of the rehabilitation patient population.41 For these early-stage patients simply learning to activate the target musculature again can prove challenging. In this context, the DAPRE protocol in conjunction with resistance machine exercises can function as an easy introduction to resistance training before progression to FF or body-weight exercises. However, based on the current literature it is likely that neither the DAPRE protocol nor resistance machine exercises are independently effective at maximally improving functional strength in a patient population at the intermediate stage of rehabilitation.
We conclude that 3 weeks of resistance training is insufficient duration to see a significant difference between different resistance training programmes. However, we recommend that the FST training programme is used in intermediate-stage rehabilitation due to its time effectiveness and lower variability in training outcome.
References
Footnotes
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Competing interests None.
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Provenance and peer review Not commissioned; externally peer reviewed.