In the context of yearly planning in rowing, coaches and sport scientists may balance small compromises in one aspect of physical development in trade-off for gains in another. For example, strength or weight training has been traditionally emphasized during the “off-season,” sequenced before the development of aerobic power (2). Over the recent decades (1970–2001), endurance volumes have increased by ∼20% and total training time to >1,100 hours a year among the rowing elite (7). With this increase in volume, emphasizing phases of strength over aerobic endurance has become problematic. Informed decisions about the value of weight training over other possible training activities in periodized plans for rowing need to be made.
Researchers have concluded that high-volume (2–3 sessions for >16 weeks) nonfatiguing (i.e., prescribing fewer repetitions) heavy resistance (≥75% 1RM) weight training, concurrent to high-volume endurance exercise, can lead to enhanced longer term (>30 minutes) and shorter term (<15 minutes) endurance performance gains, both in well-trained and in top-level endurance athletes (1,4,9,14). With regard to rowing, the leg drive and trunk swing provide almost 80% of total propulsive stroke power (17,29). Furthermore, lower-body strength has been reported as a strong predictor of 2,000-m ergometer speed (e.g., leg pressing, r = −0.69, p < 0.01) (16,19,30), and positive benefits, of clinical and practical significance, have been associated with strength development of rowers (3,4,6,8,20). However, 8 weeks of extensive endurance rowing (i.e., 250–270 km per week) was insufficient exercise alone to increase lower-body strength in elite rowers, when compared with the gains made on inclusion of weight training (e.g., leg pressing [dynamometer]: −2.9 ± 5.2%, p > 0.05; and 2.4 ± 5.4%, p < 0.05, respectively) (21). Thus, some element of lower-body weight training might be warranted to improve performance in preparation for competition, where practical.
Weight training, however, may be excluded from rowing plans on the rationale of eliminating any risk for unnecessary body mass gains, which can negatively affect the drag velocity associated with boat buoyancy (25,26). If this is the case, alternative strategies to develop or maintain strength need to be employed in rowing. In terms of the lower body, strategies used to emphasize the “leg drive” such as the towing of ropes (resisted rowing) or rowing in pairs within a 4-person crew are thought to provide a surrogate strength training stimulus highly specific to rowing. However, to the knowledge of these authors, the efficacy of such strategies to develop or to maintain lower-body strength in comparison with weight training has not been reported. Hence, the purpose of this study was to quantify changes in lower-body strength after intensive resisted on-water rowing, either incorporating weight training or rowing alone.
Experimental Approach to the Problem
A pre-post crossover research design was developed to compare changes in lower-body strength (dependent measures) from intensive resisted rowing alone or in combination with weight training (independent variable). A small population of elite rowers volunteered to participate in this 32-week study as part of their preparations preceding international competition (i.e., 2010 World Cup 2 and then 2010 World Championships). Given the small sample size, we selected dependent measures with very high intraclass correlation (ICC) moments to achieve satisfactory statistical power for investigation (i.e., ICC ≥ 0.96). We anticipated small differences in changes in the dependent measures (i.e., standardized differences in change of mean as an effect size [ES] ≤0.2 [Cohen] units) given the advanced training history and competitive level of participants. Therefore, the duration for each training intervention, and thus independent variable, was maximized (14 weeks) for the period rowers were available for the study (i.e., 32 weeks). Rowers were randomly assigned by national selectors to an initial training intervention. After a 4-week “washout” period, the alternate training method was performed (by the same rowers). Changes in lower-body strength tests (dependent measures) were used to compare adaptations from resisted rowing practices alone with weight training.
Ten international elite (all “A” finals bronze medallists at World Championships) female heavyweight rowers volunteered to participate in this study conducted “pre-competition.” The mean (SD) characteristics of these rowers are as follows: age and rowing experience, 23.3 (4.1) and 7.0 (3.9) years, respectively; height, 178.5 (4.2) cm; body mass, 74.6 (5.3) kg; and 2,000-m ergometer time, 412.2 (7.6) seconds.
Institutional review board approval for the study protocol was gained from the Auckland University of Technology Ethics Committee. Written (signed) informed voluntary consent was obtained from rowers after project information and familiarization seminars were attended. All rowers were cleared by medical staff for participation in training and testing.
Leg Pressing Dynamometry
A “Dynamic Strength Training” dynamometer (Concept2 Dyno; Concept2 Inc., Morrisville, VT, USA) was used to measure average concentric work (J) produced during 5 repetitions of leg pressing. The dynamometer provided resistance by flywheel inertia combined with air braking fans to create drag, comparable in design with a Concept2 model c rowing ergometer. The drag factor was set with 2 air dampeners opened for leg pressing. For each test, a repetition was commenced every 2 seconds (or equivalent to a rating of ∼30 repetitions per minute) to ensure all repetitions were performed within a target completion time (∼10 seconds). Three trials of each test were performed, at least 3 minutes between attempts, with the best score recorded as the test result. Previous test-retest reliability of this dynamometer strength test was as follows: coefficient of variation (CV) = 2.5%; ICC ≥ 0.97 (21).
The isometric pull was used to assess the strength of the legs, torso, and arms because previous research has shown successful national-level rowers demonstrate superior strength in this exercise (15,28). The isometric pull involved pulling against an immovable barbell adjusted to the height of the rower’s knee and held in place by the adjustable safety bars within in a power rack (Fitness Works Pty. Ltd., Auckland, New Zealand). Rowers performed the isometric pull for 5 seconds, progressively building to their maximum effort, and up to 3 minutes rest was allowed between the 3 trials permitted for assessment. Rowers were observed to ensure each attempt was performed without flexion of the lumbar spine.
During the test, the rower stood on a force platform (400 Series Performance Plate; Fitness Technology, Adelaide, Australia). Vertical ground reaction force data were collected at 200 Hz and then analyzed via the Ballistic Measurement System software (version 2009.1.4, www.innervations.com; Australia). The greatest peak force of any trial was reported as the test result. Previous test-retest reliability was CV = 3.5%; ICC ≥ 0.96 (24).
At the beginning of each training intervention, dependent strength measures (leg pressing and isometric pull) were performed. During testing, rowers were assigned to a group of 3—this allowed the appropriate work-to-rest ratio to enable sufficient recovery between trials. However, participants could notify the researchers if they needed more time to prepare or recover between tests to ensure their best performance was measured. Up to 3 trials were permitted for each test, with the maximum result reported. At the completion of the repeated 14-week training intervention, dependent strength measures were repeated (Table 1). All testing was repeated at the same time of day. A common on-water and off-water endurance taper (∼50% reduced training volume) was performed 3 days before testing, and the rowers maintained a similar diet and hydration status, monitored for the duration of the study.
All on-water rowing exercise was performed in single, double, or quadruple sculls. Endurance rowing was performed between 18 and 20 strokes per minute (spm), with a target average boat velocity of ∼80 ± 5% of world record pace for respective boat classes. Individual target training zones for heart rate (∼70–80% maximum heart rate) and lactate levels (∼1–1.8 mmol·L−1) were moderated in accordance to “utilization 2” energy substrate training parameters.
In addition, 2 intensive boat races were conducted each week that varied in distance from between 8,000 and 2,000 m, and were either fixed (e.g., 24 spm) or free rating. Races were handicapped based on estimated completion time, and timed with rowers ranked by performance expressed as a percentage of world record times for each respective boat class.
Weekly training volume was progressed using a 4-week step cycle (∼5% weekly increases in training distance), with a 3-day loading pattern repeated twice each week. Endurance rowing training distances ranged between 16 and 28 km a session, with total weekly volumes ranging from 190 to 210 km per week (including warm-up and cool-down phases performed as part of interval and resisted rowing sessions). A coach accompanied each squad of rowers to monitor training intensity and volume, and to provide technical instruction in the execution of their rowing technique.
On-water “resisted rowing” was achieved by use of “bungees” (elasticized straps wrapped around the hull attached to the gunnels) or partnered rowing (only 2 of the 4-person crew row the boat). Resisted rowing was performed twice each week. Work intervals varied from 1 to 3 minutes of resisted rowing, followed by 3–6 minutes of conventional rowing, repeated between 7 and 9 times. Stroke rating varied each repetition between 28 and 32 spm and the total interval session running up to 1 hour, with an additional 15 minutes of warm-up and cool-down row.
Weight training consisted of 1 session of maximal strength (4 exercises, 3–4 sets × 6–15 reps) and muscular power (7 exercises, 3–4 sets × 15–30 reps) each week (Table 2). The intensity of strength exercise was progressively increased so that by the final week, fewer repetitions were performed, although no sets were performed to repetition failure(9,14). To equate for additional volumes (total time) when weight training was incorporated into the interventions, 2 endurance rows were shortened in duration or distance (e.g., <60 minutes or <16 km). All other on-water training remained consistent between training phases, including resisted rowing practices.
All dependent strength measures data (leg pressing and isometric pull) were presented as mean ± SD. Data were analyzed using a spreadsheet designed for “analysis of pre-post crossover trials,” with confidence limits (CLs) set at 90% and smallest worthwhile difference or change in dependent strength measure means in standardized (Cohen) unit set to 0.2 (12). Individual best scores were tabulated for all dependent strength measures and normalized by dividing by body mass (ratio scaling). All data were log transformed before analysis to reduce nonuniformity of error and adjusted for the pretest scores of each rower as a covariate.
Percent and standardized mean changes in dependent strength measures and differences between the changes were calculated, with p values interpreted as significant where p ≤ 0.05. Magnitudes of standardized effects were calculated by dividing the appropriate between-rower SD and using a modified Cohen scale defined as follows: <0.2 = trivial; 0.2–0.59 = small; 0.6–1.19 = moderate; 1.2–1.99 = large; and >2.0 = very large (11,13). An effect trend was deemed unclear if confidence intervals for standardized effects overlapped the thresholds for small positive and negative effects (i.e., 0.1 Cohen units).
The percentage change in group means (±SD) and differences in dependent strength measures after 14 weeks of weight training or rowing alone, adjusted for pre-test scores, can be observed in Table 3. Differences in body mass changes observed after weight training (0.5 ± 2.8%, p = 0.78) and resisted rowing alone (−0.6 ± 4.8%, p = 0.78) were trivial (ES = 0.17 ± 0.61, p = 0.61). After resisted rowing alone, leg pressing (−1.0 ± 5.3% p = 0.51) did not change (i.e., was maintained); in contrast, after weight training, a moderate increase (9.1 ± 8.5%, p = 0.01) in leg pressing strength was observed (ES = 0.72 ± 0.62, p = 0.03). Isometric pulling strength, although showing a trend to increase, was maintained on average whether 14 weeks of resisted rowing alone (5.3 ± 13.4%, p = 0.28) or in combination with weight training (12.3 ± 8.6%, p = 0.10) was performed. The likelihood that observed trend increases in isometric pulling was moderately greater after weight training was unclear (ES = 0.56 ± 1.69, p = 0.52).
After a period of prioritization over the off-season, a rower may have little time or sufficient energy to commit to further strength training. In these circumstances, weight training might be ceased and replaced with intensive resisted on-water training practices such as towing ropes or paired crew rowing. Dependent on total volumes, resisted rowing may offer the potential for increased muscular strength, power, or endurance. Additionally, any gains in lean body mass or strength would logically seem highly specific to the kinetic and kinematics requirements of rowing. Such practice may also be beneficial in terms of ensuring that any lower-body strength believed to enhance performance gained off-water may continue to improve or, at the very least, be maintained. However, the main finding of the present study was that without the inclusion of weight training, the lower-body strength development of individual rowers ceased (−1.0 ± 5.3% p = 0.51). In other words, resisted rowing resulted in maintenance of lower-body strength at best. Conversely, the inclusion of 2 weight-training sessions each week resulted in a moderately greater increase (9.1 ± 8.5%, p = 0.01) in lower-body strength (ES = 0.72 ± 0.62, p = 0.03). Therefore, rowers seeking further gains in lower-body strength as part of preparations for competition should not rely on resisted on-water rowing practices for such adaptations.
To the knowledge of these authors, strength, power, or muscular endurance adaptations after intensive on-water resisted rowing have not previously been published. Past intervention studies involving parallel trials with weight training contrasts in rowing have not published strength data for non–weight-trained controls (8). However, what was apparent from the literature was that on-water rowing was unlikely to achieve the mechanical, metabolic, and hormonal stimuli required to maintain strength for extended periods (18). For example, the isokinetic leg strength of elite oarsmen had effectively declined 12–16% by the end of a competition period after weight training was ceased for 8 months (10). In contrast, at sufficient intensity (i.e., 73.0–79.3% of predicted 1RM), oarswomen were able to increase leg pressing maximal strength development ∼10–20% over 6 weeks, whether 1 or 2 weight-training sessions were performed each week (4). That is, weight training need not be too time consuming or physically demanding, in build up to competition.
In terms of the present crossover study, significant lower-body strength gains (scaled relative to body mass) were observed when rowers performed weight training (leg pressing: 9.1 ± 8.5%, p = 0.01). In contrast, for a period of equal training volumes, rowers were unable to improve leg strength (leg pressing: −1.0 ± 5.3%, p = 0.51). Therefore, if it is believed a rower or crew may benefit from increased lower-body strength relative to their body mass, they would be moderately worse off using on-water rowing techniques after 14 weeks, on omission of weight training (adjusted difference: −9.3%; 90% CL = −15.1 to −3.0%, p = 0.03). Furthermore, it was postulated that off-water strength training may be excluded from training or closer to competition on the rationale of eliminating any risk for unnecessary body mass gains, which can negatively affect the drag velocity associated with boat buoyancy in rowing (25,26). Our results suggested that differences in body mass changes were trivial (ES = 0.17 ± 0.61, p = 0.61) and there was no advantage gained from on-water resisted rowing alone (body mass change: −0.6 ± 4.8%, p = 0.78) on omission of weight training (0.5 ± 2.8%, p = 0.78). We concluded that these variations in body mass were more likely to be associated with a rower’s hydration status or dietary energy balance.
Interestingly, coaches have reported to the authors acute improvements in the distance attained for a set number of strokes (at an equivalent fixed rating) for the work interval immediately subsequent to the resisted rowing, than without the use of such strategies. The benefits associated with these modest improvements observed on-water, however, did not amount to any chronic change in lower-body strength. Although there may be acute performance benefits associated with such observed trends, on the basis of the present data, we could only conclude that specific on-water resisted rowing practices were inadequate to develop leg strength.
To elicit a sufficient training stimulus to develop strength concurrent to technique development, it may be that the external work performed, and thus physiological responses to resisted rowing, necessitate greater overload. For example, our investigations with force gates (Powerline; Peach Innovations Ltd., Cambridge, United Kingdom), used to monitor the training of these rowers, confirmed increases in average propulsive stroke forces during resisted rowing. However, given a faster rate of energy utilization associated with higher intensity work intervals (in comparison with steady-state extensive endurance rowing), total session training volumes (duration) were reduced. Thus, we suspect that any potential advantage associated with chronic strength development was limited with resisted rowing because of the inability to sustain any real net increase in either intensity (power) or volume of exercise.
Greater drag loads (i.e., more bungees), training volumes, or both may be required to develop maximal strength, should that be the intent of training. However, consideration must also be given to any increased risk for injury to the low back (e.g., vertebral segments) given the trends we observed in isometric pull strength from rowing (5.3 ± 13.4%, p = 0.28). Rowing involves repeated flexion cycles of the spine that exacerbate the risk for disc injury (5,22,23,27). It may be the case that any further increase in training intensity (drag load) or volume (number of work intervals) overexposes rowers to the risk for low back injury. In conclusion, on the basis of this study, 14 weeks of intensive on-water training including resisted rowing maintained but was not able to increase the lower-body muscle strength of rowers, which was in contrast to the effective integration of weight training.
Elite rowers or coaches might consider the incorporation of high-intensity nonfatiguing weight-training exercise as part of periodized training plans, if an increase in the lower-body strength of a rower is desired, without any change in body mass. Furthermore, weight training permits the distribution of training loads to targeted areas of the muscular system such as the lower body, overcoming potential limitations associated with rowing exercise when injured (e.g., low back). However, lower-body strength can be maintained but not increased over 14 weeks by the use of intensive on-water training and resisted rowing.
This study was made possible as a result of the funds awarded through a Prime Minister’s Scholarship 2010 (a New Zealand Government grant). The authors have no conflicts of interest to report, or professional relationships with companies or manufacturers who will benefit from the results of the present study. No funding from the National Institutes of Health, Welcome Trust, Howard Hughes Medical Institute, or others was received for this work. Results of the present study do not constitute endorsement by the authors or the National Strength and Conditioning Association.
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