Acute and Long-Term Effects of Concurrent Resistance and Swimming Training on Swimming Performance

ry-land resistance exercise (RT) is routinely applied concurrent to swimming (SWIM) training sessions in a year-round training plan. To date, the impact of the acute effect of RT on SWIM or SWIM on RT performance and the long-term RT-SWIM or SWIM-RT training outcome has received limited attention. The existing studies indicate that acute RT or SWIM training may temporarily decrease subsequent muscle function. Concurrent application of RT-SWIM or SWIM-RT may induce similar physiological alterations. Such alterations are dependent on the recovery duration between sessions. Considering the long-term effects of RT-SWIM, the limited existing data present improvements in front crawl swimming performance, dry-land upper and lower body maximum strength, and peak power in swim turn. Accordingly, SWIM-RT training order induces swimming performance improvements in front crawl and increments in maximum dry-land upper and lower body strength. Concurrent application of RT-SWIM or SWIM-RT training applied within

Considering the long-term effects of RT-SWIM, the limited existing data present improvements in front crawl swimming performance, dry-land upper and lower body maximum strength, and peak power in swim turn. Accordingly, SWIM-RT training order induces swimming performance improvements in front crawl and increments in maximum dry-land upper and lower body strength. Concurrent application of RT-SWIM or SWIM-RT training applied within a training day leads in similar performance gains after six to twelve weeks of training. The current review suggests that recovery duration between RT and SWIM is a predisposing factor that may determine the training outcome. Competitive swimmers may bene t after concurrent application with both training order scenarios during a training cycle. Keywords:well-trained swimmers; dry-land training; endurance; training order 1. Introduction Competitive swimmers participate in dry-land training sessions aiming to improve several aspects of conditioning and increase in-water propulsive force [1–3]. During a dry-land session, swimmers may apply resistance training (RT) including various modes of exercise and speci c apparatus [4–6]. Typically, RT may focus on muscular endurance with low external loads (3–4 sets, >12 repetitions, 40–60% of 1 repetition maximum (1-RM) [6–9] or maximum strength using high loads (3–5 sets, 3–5 repetitions, >85% of 1-RM, 2–3 min rest) [3,4,10–12]. Within a training microcycle, all dry-land sessions should be incorporated and adjusted according to swimming training sessions. Then, coaches should plan two or more RT sessions each week, prior to or following in-water swimming training (SWIM). Such a microcycle training plan is regularly repeated during a mesocycle or longer periods of training. There is evidence that long-term concurrent application of RT and SWIM training sessions may improve performance compared to SWIM training alone, and this has been extensively reviewed and supported with experimental ndings [2,7,8,10,13,14]. However, several studies have indicated that concurrent training might pose a negative Sports2022,10, 29.

Sports2022,10, 29 2 of 15 in uence on various aspects of performance, and this is likely attributed to the distinct molecular responses activated following RT or endurance training [15,16]. Thus, in swimming training practice, the combination of RT and SWIM may create a con icting environment within the skeletal muscle when it applies on the same day. Important factors that may determine the performance outcome is the content of training and the duration of recovery period provided between RT and SWIM sessions. For instance, compared to a maximum strength RT session, a muscular endurance RT session may cause a higher metabolic perturbation due to the short resting interval between sets and the higher volume of training [17–21]; whereas both RT training paradigms may induce similar decrements in phosphocreatine and glycogen stores [20–23]. Moreover, swimming training may include long-duration endurance and/or short-duration high-intensity bouts within a session in many cases combined with in-water RT [24,25]. Then, a variety of energetic, metabolic, and cardiovascular responses of a SWIM training session should be combined with neuromuscular and metabolic effects of the previous or subsequent RT training session, and vice versa [26–28]. Despite the growing evidence for a bene cial effect of RT on swimming performance, it is unclear whether RT should be applied prior or following a SWIM session. It has been recently reported that coaches prefer to apply SWIM before an RT session (SWIM-RT) [26], although it might be worthwhile pointing out that RT prior to SWIM (RT-SWIM) or RT only might also be applied depending on the coach's preference. In both scenarios of concurrent resistance and swimming training, the recovery period between sessions may vary. This is because swimmers train in the water twice a day during long periods of their preparation. Then, a morning SWIM session may be followed by an RT session (SWIM-RT); however, one more SWIM session may also be applied a few hours later (RT-SWIM). Despite the routinely applied practice of the RT-SWIM or SWIM-RT order within a training session, the combined acute and long-term effect of these training orders has received limited attention in swimming research.

preparation. Then, a morning SWIM session may be followed by an RT session (SWIM-RT); however, one more SWIM session may also be applied a few hours later (RT-SWIM). Despite the routinely applied practice of the RT-SWIM or SWIM-RT order within a training session, the combined acute and long-term effect of these training orders has received limited attention in swimming research. The purpose of the current review is to summarize the physiological responses and performance outcome following acute RT- SWIM or SWIM-RT applied within the same day and evaluate the subsequent long-term adaptations in well-trained swimmers. 2. Materials and Methods A narrative review that examined the order effect of RT-SWIM or SWIM-RT in swim- ming performance was carried out. Two of the authors searched the databases Medline, Google scholar, and Sport Discus by September 2021, using the combinations of relevant keywords: “concurrent training” AND “order effect”, “concurrent training” AND “ath- letes”, “concurrent training” AND “swimming”, “concurrent training” AND “water polo“, “concurrent training” AND “acute effect” AND “athletes”, “concurrent training” AND “long-term effect” AND “athletes”. Moreover, the content of books of proceeding of the Biomechanics and Medicine Congresses from 1983 to 2018 were searched. The searches identi ed 416 potentially relevant studies. Final selection was based on the following inclusion criteria, (a) participants should be competitive swimmers, (b) studies should clearly mentioned the RT-SWIM or SWIM-RT order in swimming or in other aquatic sport, (c) studies should refer that concurrent training of RT-SWIM or SWIM-RT order applied within the same day, and (d) the recovery period between the training sessions RT or SWIM was up to eight hours. The number and selections of studies included in this narrative review focusing on concurrent RT-SWIM or SWIM-RT training order and sports performance with physiological characteristics relevant to swimming and water polo are presented in Figure. Moreover, the training level of swimmers that were included in the narrative review was classi ed according to previously suggested criteria [29] and is presented in Table.

characteristics relevant to swimming and water polo are presented in Figure. Moreover, the training level of swimmers that were included in the narrative review was classi ed according to previously suggested criteria [29] and is presented in Table.

Sports2022,10, 29 3 of 15Sports 2022, 10, x FOR PEER REVIEW 3 of 14 Figure 1. Flow chart of the literature search and studies used in the review according to inclusion criteria. RT: dry-land resistance training, SWIM: swimming training, n indicates the number of stud- ies. Table 1. Studies included in the narrative review aiming to demonstrate the acute and long-term order effect of dry-land resistance (RT) and swimming (SWIM) training. Time Effect Swimming Studies Water Polo Studies Acute [11] [30] Long-term [4,7,8 ,31] [32,33] Number of included studies 5 3 Table 2. Classification of swimmer’s training level. Studies Athletes’ Level Training Background in RT (Years) Training Routine (Times/Week) Competing Level [11] Highly- Trained ≥3 6 National [30] Highly- trained ≥6 ≥6 National [7] Highly- trained - - National [8] Highly- Trained - - National [32] Highly- trained ≥5 ≥6 National [33] Elite/ international ≥5 ≥6 National/ International [4] Elite/ international ≥2 ≥6 National/ International [31] Highly- trained ≥2 ≥5 National ≥: greater or equal, -: undefined, RT: dry-land resistance training. Figure 1. Flow chart of the literature search and studies used in the review according to inclusion criteria. RT: dry-land resistance training, SWIM: swimming training,nindicates the number of studies. Table 1.Studies included in the narrative review aiming to demonstrate the acute and long-term order effect of dry-land resistance (RT) and swimming (SWIM) training. Time Effect Swimming Studies Water Polo Studies Acute [11] [30] Long-term [4,7,8,31] [32,33] Number of included studies 5 3 Table 2.Classi cation of swimmer's training level. Studies Athletes' Level Training Background in RT (Years) Training Routine (Times/Week) Competing Level [11] Highly- Trained 3 6 National [30] Highly- trained 6 6 National [7] Highly- trained - - National [8] Highly- Trained - - National [32] Highly- trained 5 6 National [33] Elite/ international 5 6 National/ International [4] Elite/ international 2 6 National/ International [31] Highly- trained 2 5 National : greater or equal, -: unde ned, RT: dry-land resistance training.

5 6 National [33] Elite/ international 5 6 National/ International [4] Elite/ international 2 6 National/ International [31] Highly- trained 2 5 National : greater or equal, -: unde ned, RT: dry-land resistance training.

Sports2022,10, 29 4 of 15 3. Concurrent Resistance and Swimming Training: Acute Physiological Response and Performance Outcome in Swimmers Two studies in swimming have examined the effect of RT and SWIM order on swim- mer's performance. To date, no study has examined the SWIM-RT order. In particular, these studies have used a repeated measures design and applied a counterbalanced [11] or randomized testing order [30]. Moreover, maximum strength (high loads) or muscular endurance (low loads) RT sessions were applied before a SWIM session that consisted of different training modes such as endurance [11] or repeated sprints [30]. Training char- acteristics of included studies in swimming that examined only the RT-SWIM order are reported in Table. 3.1. Acute Effects of RT–SWIM A recent study examined the effect of an RT session (3 sets, 3 repetitions, 85% of 1-RM, 4 min rest) on a subsequent endurance SWIM set of 5 400 m repetitions applied at a constant speed corresponding to 4 mmol L 1 [11]. Performance during the 5 400 m was not affected by the RT-SWIM combination compared to that in the control condition (no RT before SWIM session). In addition, the force during a 10 s tethered swimming sprint that was performed 5 min before starting the 5 400 m set was no different compared to that in the control condition (no RT) [11]. Applying the RT session at high load (80% of 1-RM) 20 min before SWIM decreased performance in the best and mean time during 8 25 m repeated sprints [30]. The decrement in mean performance time was attenuated, while the best time was not affected following a low-load session (50% of 1-RM) [30]. However, it should be noted that the total volume of RT sessions was not equal (3 sets of 8 repetitions at 50% of 1-RM vs. 3 sets of 8 repetitions at 80% of 1-RM) allowing a likely better recovery following the low-load session. The recovery period between RT and SWIM sessions varied from ~20 to ~40 min, and this may have affected metabolic restoration when concurrent training was applied in the same training unit.

equal (3 sets of 8 repetitions at 50% of 1-RM vs. 3 sets of 8 repetitions at 80% of 1-RM) allowing a likely better recovery following the low-load session. The recovery period between RT and SWIM sessions varied from ~20 to ~40 min, and this may have affected metabolic restoration when concurrent training was applied in the same training unit. Despite the limited number of studies in swimming, it is likely that a 30 to 40 min recovery period between RT and SWIM allows adequate recovery of blood lactate concentration, heart rate, and oxygen uptake close to baseline before the start of a SWIM session [11]. However, blood lactate concentration was increased by 3% towards the end of the SWIM session when RT was preceding SWIM [11]. Possibly, maximum-strength RT enforced swimmers to a higher activation of anaerobic metabolism compared to that of the control condition (SWIM training only) aiming to maintain the required swimming speed during an endurance SWIM set [11]. It seems that a 30 to 40 min recovery interval between RT and SWIM sessions allows adequate removal of fatigue-related metabolites; any effect of an RT session, however, might be noticed later during the last part of a SWIM session, and it is likely attributed to neuromuscular fatigue [11,34,35]. The ndings presented in studies applying acute RT-SWIM sessions suggest that when maximum strength dry-land RT is performed 20 min before a SWIM session, a decrement in best and mean performance time may occur during high-intensity swimming training [30]. On the contrary, when similar dry-land RT training was performed ~40 min prior to endurance training, there was no impact on swimmer's endurance performance [11]. Coaches should be acknowledging the recovery period between RT and SWIM and the following SWIM session mode when it is applied concurrently on the same day.

Sports2022,10, 29 5 of 15 Table 3.Acute physiological and performance effects of concurrent resistance (RT) and swimming (SWIM) training order. RT Set Characteristics Studies Participants Day Time of Training Number of Sets and Repetitions Exercises Set Duration SWIM Content Order of Training Recovery Time between RT-SWIM Findings [11] n= 12, M, Well-trained swimmers, 19 2 y Morning: RT and SWIM sessions 3 sets 5 reps @ 85% 1-RM with 4 min rest Bench press Seated pull rowing Half squat (90 ) ~45 min 5 400 m front crawl swimming @ speed corresponding to 4 mmol L 1 RT-SWIM 40 min RT-SWIM vs. SWIM only: similar oxygen consumption and heart rate. Increased lactate responses during RT-SWIM [30] n= 9, M, Competitive water polo players, 22 2 y Not reported 3 sets 8 reps @ 50% 1-RM with 2 min rest and 3 sets 8 reps @ 80% 1-RM with 2 min rest Bench press Leg press 20 min 8 25 m all out front crawl with 30 s rest interval RT-SWIM 20 min Best time: RT (50% 1-RM)-SWIM and SWIM only better vs. RT (80% 1-RM)-SWIM Mean time: No difference RT (50% 1-RM)-SWIM vs. RT (80% 1-RM)-SWIM. SWIM only better vs. RT (80% 1-RM)-SWIM RT: dry-land resistance training, END: endurance, 1-RM: 1 repetition maximum, s: seconds,nindicates the sample size in each study, M: males, F: females, y: years.

Sports2022,10, 29 6 of 15 3.2. Acute Effects of SWIM-RT The search applied in the current review revealed the lack of studies testing the SWIM- RT order despite it being a likely approach during a real training setting. However, any homeostatic or metabolic and neuromuscular effect of the swimming session may affect ef - ciency, physiological responses in the following RT, and subsequent adaptations [26,36,37]. Interestingly, a SWIM training session (6 repetitions 5 min front crawl) at an intensity 105% of critical speed (very heavy intensity domain) decreased maximal torque of shoulder internal rotators by ~23% [38] and a short-duration high-intensity SWIM of 4 50 m at extreme intensity domain (maximum effort) decreased isometric force and activation of shoulder muscles measured following 5 min of recovery [39]. Additionally, it is well-known that SWIM session duration and intensity may decrease muscle glycogen [40], affecting resynthesis of energy-providing substrates and performance in a subsequent high-intensity type of exercise [41]. A decrement of ~20% in average force production during maximal bilateral isometric force in endurance-trained athletes [42] and in back squat strength in resistance-trained athletes [43] was reported following 60 min steady-state running at 80% of maximum oxygen consumption preceding RT, compared to that with the reverse order. Considering the comparable ndings between SWIM and running, it may suggest that intensity of a SWIM session may decrease maximum strength of swimmers due to neuro- muscular fatigue [39–43]. Moreover, metabolic recovery is expected to affect subsequent performance, therefore, depending on the intensity and duration of SWIM training, heart rate, and blood lactate are expected to recover near to baseline values within 15–20 min [44]. Collectively, the above information indicates that swimmers starting an RT session following SWIM face decreased glycogen levels [40] and impaired muscle function [38,39]. In such a case, RT session performance and subsequent long-term adaptations may be compromised [45,46]. The overall effect of SWIM-RT may also be dependent on the duration of recovery between sessions, affecting restoration of physiological parameters. It should be pointed that long- term application of SWIM-RT training may induce adaptations both in skeletal muscle (i.e., increase muscle

muscle function [38,39]. In such a case, RT session performance and subsequent long-term adaptations may be compromised [45,46]. The overall effect of SWIM-RT may also be dependent on the duration of recovery between sessions, affecting restoration of physiological parameters. It should be pointed that long- term application of SWIM-RT training may induce adaptations both in skeletal muscle (i.e., increase muscle fibers area, capillary density) and in cardiovascular function (i.e., increase cardiac output and stroke volume) [15,16,47]. These potential adaptations may lead to a faster recovery rate between SWIM and RT sessions after a training period. 3.3. A Comparison of the Acute Training Orders There is no published data in swimming research directly comparing SWIM-RT and RT-SWIM acute effects. In other sports paradigms, applying endurance exercise at mod- erate intensity (70% of maximum oxygen uptake) before RT following 10 min recovery between sessions results in a higher blood lactate concentration at the end of combined endurance-RT sessions compared with that of RT-endurance exercise in resistance-trained individuals [48,49]. In contrast, both blood lactate concentration and oxygen uptake in- crease when a resting period of 5 min is applied between RT-endurance training compared with that of the endurance-RT order [50]. However, when the resting period between RT- endurance and endurance-RT training orders was 15 min, similar blood lactate responses were observed [34]. Whatever the case, blood lactate response re ects the effect of the last session (RT or endurance) and may be used as an indicator of exercise intensity but has limited value to judge the effectiveness or recovery following RT and endurance orders. Considering the previously mentioned ndings, we hypothesize that a SWIM session preceding an RT session in the same training day may induce higher metabolic response compared to that expected in a subsequent RT. The last evidence should be tested with competitive swimmers. The lack of information concerning swimming literature and the need for further research is illustrated in Figure.

The review evaluates the effects of training order on swimming performance.