Normality of the distribution for outcome measures was tested using the Kolmogorov-Smirnov test. All the values are reported as mean ± SD. The differences in 1RM and MT between groups were compared with a mixed model 2-way ANOVA (group [FULL, PART, and CON] × time [pretest and posttest]) followed by the least significant difference post hoc procedure whenever necessary. Statistical significance was set at p ≤ 0.05. Data were analyzed using the Statistical Package for Social Sciences (SPSS) version 17 software (SPSS Inc., Chicago, IL, USA). Also, the effect size was calculated for strength and MT gains according to Rhea (19) for resistance training effects.
The results from the 1RM strength tests are presented in Table 1. The pretest 1RM initial scores were the same (p > 0.05) regardless of the 3 groups tested (FULL, PARTIAL, CON); however, the 1RM analysis of variance (ANOVA) revealed a significant interaction of group by time. This was followed-up with three 1 × 2 ANOVAs for time for each group and revealed a significant (p < 0.05) increase in 1RM for both the FULL and PART groups but not for the CON group (p = 0.25). In FULL and PART, 1RM significantly increased 25.7 and 16.0% above baseline values, respectively. The effect size for the changes in strength was moderate to large (1.89) for FULL and small (0.87) for PART.
The pretest MT initial values were the same (p > 0.05) regardless of the 3 groups tested (FULL, PARTIAL, CON); however, the MT ANOVA also revealed a significant interaction of group by time. This was followed up with three 1 × 2 ANOVAs for time for each group and revealed a significant (p < 0.05) main effect for time for both FULL and PART groups but not for the CON group (p = 0.36) (Figure 4). In FULL and PART, MT significantly increased 9.52 and 7.37% from baseline values, respectively. The effect size for the changes in MT was 1.09 for FULL and 0.57 for PART.
The purpose of this study was to compare the effects of FULL vs. PART ROM resistance training on strength and MT of the elbow flexors. Although, the training volume from the full ROM group was 36% lower than that of the partial ROM group, the results of this study suggest that, for strength, lifting through a full ROM was superior to that through a partial ROM. Another main finding from our study was that the training volume used was sufficient to improve the MT of the right arm elbow flexors for both training groups but not for the CON group. On the other hand, the MT for full (9.7%) was greater than that for the CON (−2.4%) but not significantly (p = 0.07) different from partial ROM (7.8%).
The effects of different resistance training ROM on neuromuscular responses have been the subject of a few acute (6,17) and chronic studies (7,10,11,15,16). The first study investigated the effect of different ROM training on strength gains at specific angles and showed that muscle strength improves more at the joint angles trained and not completing the full ROM may result in weakness at untrained angles (10). On the other hand, the same authors later reported that partial training also improves full ROM strength in the lumbar extensor muscles (10). Other studies have assessed the effects of different ROM training on full ROM strength gains. Massey et al. (16) compared the effects of partial ROM and full ROM training on the development of maximal bench press strength. They divided their male subjects into 3 groups. One group trained with full ROM, another group trained with partial ROM, whereas the last group trained with mixed ROM (partial and full). They found no difference in 1RM bench press strength gains between groups. These results are not in agreement with those of this study in which the full group's strength increased more than the partial group's (25.7 and 16.0%, respectively). Interestingly, another study (15) using female subjects found similar results to those of our study in that bench press strength gains when training through a full ROM (34.8%) were superior to those through a partial ROM (22.5%) and mixed (23.1%) training. They speculated that the differences in results could possibly be because of the relative lack of experience of the women subjects. These results are in agreement with those of this study, which also used naive subjects.
Recently, Clark et al. (7) using 2 groups of athletes with extensive resistance training backgrounds investigated the effects of 5 weeks of mixed ROM training, consisting of partial ROM training performed in a different phase of the ROM for each set, on isokinetic and isometric bench press and ballistic bench throws. They compared these with a control group performing full ROM bench press. Their results revealed that the mixed ROM group significantly improved bench throw displacement (15.5%) under the full ROM testing condition, despite there being no significant increase in peak force during the full ROM countermovement (+1.6%). In contrast, the mixed ROM group produced significantly greater peak force (+15.7%) in the half ROM countermovement throws. Interestingly, they reported a decrease in bench throw displacement (−3.7%), bench throw peak force (−1.8%), and half ROM bench throw peak force (−3.5%) in the full ROM group. Thus, they concluded that mixed ROM training is better than full ROM training to improve an athlete's reactive strength and dynamic force performance at shorter muscle lengths. The results of Clark et al. (8) and Massey et al. (16) are, in part, not in agreement with ours and the Massey et al. (15) findings. The differences may be related to the subjects training status. Massey et al. (16) used recreationally trained subjects, and Clark et al. (7) used well-trained athletes, whereas this study and the Massey et al. (16) study used only naive subjects.
Another explanation may be that, in skeletal muscle fiber, the amount of tension generated during a contraction depends on the number of pivoting crossbridges in the sarcomeres along the myofibrils. The tension produced by the entire muscle fiber can thus be related to the length of an individual sarcomere, which is related to the joint angle. Within the optimal range of sarcomere lengths, the maximum number of crossbridges can form and the tension produced is greatest. Thus, the force produced when resistance training at different ROMs can vary according to the angle trained. This may have impacted our results as one major difference between this study and other studies was that in our study partial ROM subjects trained the elbow flexion exercise through the midrange of ROM (50–100° of elbow flexion − 0° full extension), whereas the full group trained from 0 to 140°. Other studies have trained partial ROM using the initial or end range of the ROM (10,11), mixed variable ROM (8), or beyond the sticking point (2–5 in. from the full extension of the elbow) of the bench press exercise (15,16). Therefore, in this study, the partial group trained through the ROM near of optimal angle of the elbow flexion strength curve (14). Furthermore, in this study, the exercise used was a single-joint exercise (arm curl), whereas the other studies used a multijoint exercise (bench press). This is an important point because during a multijoint movement, different muscles contract through different lengths throughout the full ROM, and they are not all at optimal lengths for force production. Therefore, at any given joint angle, some muscles may produce their maximal force whereas other muscles are less than optimal.
Thus, based on our results and the results of previous studies, it can be suggested that because athletes are often required to perform countermovements at different ROM levels during sport, they may benefit from resistance training programs that use various ROM movements. On the other hand, beginners may benefit from training with full ROM because it can better improve full ROM strength and reduce the risk of sustaining an injury. Previous studies have revealed that both the load lifted and peak force output increase as the ROM of the resistance exercise is decreased (6,17). In this study, the risk of sustaining an injury and developing joint stress was probably reduced in the full ROM group when compared with that in the partial group given that the partial group lifted approximately 36% heavier loads than the full group did. Also, at a constant rate of contraction, limiting the ROM during a resistance exercise session would restrict blood flow and allow an increased number of repetitions to be performed in a given amount of time. Together, these factors may increase cardiovascular, blood lactate, and perceived exertion responses (22).
To our knowledge, this was the first study to assess the effects of different ROM resistance training on MT gains via ultrasound. It is generally accepted that there is a delay before the onset of muscle hypertrophy and that initial strength gains primarily result from the adaptation of neural factors (1). The force that a muscle exerts depends on the amount of motor unit recruitment and the rate at which motor neurons discharge action potentials (rate coding). However, muscle hypertrophy adaptations assessed with imaging techniques such as ultrasound (1,5,23), computerized tomography (8), or magnetic resonance imaging (4,12) have typically been found only after 8–12 weeks of resistance training. Thus, we can suggest that part of the strength gains in both training groups in our study may be because of muscle hypertrophy. Also, it is important to mention that the magnitude of our treatment effect for MT was almost twice as greater for full (1.09) when compared with partial ROM (0.57). This finding is important because the effect size, in the practical point of view, enables this study to suggest that training using full ROM may have a greater impact on MT than training at partial ROM in untrained individuals. Furthermore, we may also hypothesize that the lack of difference in MT between groups could be related to low training duration, training frequency, or sensitivity of the ultrasound measurement system. According to Seynnes et al. (21), it seems likely that the often described delay in onset of muscle hypertrophy observed in previous studies is partly because of the sensitivity of the method used to detect hypertrophy.
In summary, it was concluded that full ROM resistance training protocols are better than partial ROM for increasing full ROM strength of the elbow flexors in untrained individuals. Although the purpose of our study was to compare full vs. partial ROM on the development of full ROM strength, a potential limitation of this study is that the 1RM strength test was not conducted at partial ROM. Previous research reported that training at restricted angle of the training movement does increase strength within that specific ROM (10,11). As a result, we would expect that the partial group in this study would have greater strength gains during the partial 1RM test because of specific angles and also higher training loads lifted. Thus, future investigations should focus on the effects of different ROM training volumes and durations on muscle strength and hypertrophy. Also, it would be important to investigate if different ROM strength training is influenced by the exercise and muscle group used (i.e., single- vs. multijoint).
The use of a proper ROM in resistance training exercises is essential for strength and muscle mass gains in novice lifters. Thus, it is important that strength coaches and exercise professionals emphasize the use of full ROM execution during strength exercises in the early phase of a strength training program in naive subjects. Furthermore, the use of full ROM may lead to less psychological and bone joint stress, because full ROM uses a lesser load for the same number of repetitions than partial ROM does. However, partial ROM can be used in later stages of training or by athletes. Also, as suggested by Clark et al. (7), training at variable ROM appears to be a beneficial component in an athlete's attempt to achieve optimal sporting performance.
The authors wish to confirm that the present experimental methods comply with the current laws of the country in which they were performed. The authors wish to confirm that there is no conflict of interest associated with this publication and that there has been no significant financial support for this work that could have influenced its outcome.
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Keywords:© 2012 National Strength and Conditioning Association
full range of motion; partial range of motion; 1 repetition maximum; ultrasonography; strength training