1. Introduction
Many sports involve closed-skill actions that can be performed by athletes without the influence of an opponent (i.e., in a self-controlled and self-paced manner) rather than being performed in response to an external event (i.e., in an environmentally controlled and externally paced manner) [
1,
2]. Serves that bring the ball into play (e.g., in volleyball and tennis) are prototypical examples of such self-controlled actions. Successful serves can lead to immediate point gains, while service errors lead to loss of points. In addition, the quality of the serve (i.e., velocity and precision) can be crucial for succeeding in the subsequent rally, as it determines how difficult it is for the opponent to receive the serve and to structure the own game. Accordingly, the tactical focus on scoring points through one’s own serves in volleyball is increasing [
3].
However, an optimal serve requires the smooth initiation of a complex sequence of various motor activities. At least five separate movement phases can be differentiated in volleyball serves (i.e., windup, cocking, acceleration, deceleration, and follow-through), which together take less than two seconds [
4]. The corresponding biomechanical processes must first be acquired and then continually improved [
5]. For instance, volleyball players gradually develop better coordination patterns of their shoulder, elbow, and wrist movements as they gain service expertise, resulting in improved patterns that differ substantially from the coordination patterns observed among novice players [
6]. Improving these coordination patterns is not only relevant from a success maximization perspective: electromyographic analyses show that substantial forces act on the shoulder area during service [
7], and poor coordination can thus lead to serious injuries in this area particularly [
8]. Thus, both success and injury prevention call for improving the serving performance as a central training objective.
Volleyball serves thus constitute an important example for a performance that is essentially self-controlled and yet difficult to improve. This raises the question of whether and how conveying specific self-control strategies to athletes might affect their service performance [
9]. Self-control strategies are defined as targeted adjustments of one’s actions in order to obtain a goal [
10]. This involves either the prevention of an unwanted response (e.g., jumping off too early or too late after tossing up the ball) or the elicitation of a wanted response (e.g., adopting a greater stride length if the ball is too far away). From this perspective, any action involved in a volleyball serve can be adjusted by means of self-control strategies. It is not obvious, however, whether conveying self-control strategies to athletes affects their service performance for better or for worse, or whether there is no effect on performance at all (e.g., because the biomechanical sequence has been automatized by training). Research on self-controlled action is commonly limited to artificial laboratory tasks, leaving gaps in our knowledge about how self-control strategies might affect complex behaviors in more naturalistic settings. Addressing this issue with a focus on volleyball serves is paramount for training and competition as coaches should be aware of both positive and negative effects on performance when conveying self-control strategies to their players.
One fundamental strategy is setting goals or goal intentions [
11], defined as specifying desired end states that a person attempts to reach. Goals emphasize the execution of actions or the achievement of outcomes and typically have the format "I want to perform action A / obtain Outcome O!". Setting goals commonly increases the probability of successfully implementing actions [
12]. In the domain of sport, too, the effectiveness of goals has been demonstrated [
13,
14]. A second, more elaborate self-control strategy is the formulation of if-then plans (implementation intention) [
15,
16] in addition to a goal, which specifies exactly how one wants to reach the desired end state. Specifically, a plan connects an action with the occurrence of a specific situation: "If situation S occurs, then I will perform action A!". Making plans raises the probability of successfully performing an action [
16,
17]. However, while planning is a promising strategy in sports, its effectiveness for improving performance remains to be explored [
18].
Goal setting and planning are particularly suited for investigating the effects of providing self-control strategies in applied sport settings. First, both goal setting and planning are well-established strategies in the self-control literature and consistently benefit performance across various domains [
17]. Second, goals and plans are simple strategies that should be easily conveyed to athletes without requiring an extensive intervention [
18]. Third and related, it seems likely that many coaches provide goals and plans as self-control strategies without necessarily being aware of it. For instance, instructions to "toss the ball higher" or "if you have tossed the ball too far in front of you, then increase your stride length" are essentially goals and plans, respectively, according to the above definitions. Thus, it is paramount to investigate whether and how conveying these strategies to athletes affects their performance.
Fortunately, the extensive research on goals and plans allows to derive specific and testable predictions in the context of volleyball serves. While both goals and plans typically benefit performance, planning is commonly even more effective than goal setting across domains [
16,
17]. It is therefore plausible to expect generally better service performance when if-then plans are conveyed to athletes compared to goals. Moreover, goals and plans have consistently been shown to differ in the extent to which they allow an action to be performed automatically e.g., neuroimaging studies [
19,
20,
21], which permits hypotheses regarding the temporal development of performance after goal setting and planning. Specifying an action as a goal is assumed to instigate top-down processes that require continuous attention and cognitive processing because the when, where, and how of its execution are not specified [
19,
22]. According to this argument, athletes who are instructed to set goals to perform a certain action during service should need to explicitly attend to and think about performing these actions. This might withdraw their attention from other important actions during the serve, akin to the effects of conscious intrusions during the performance of well-trained actions (i.e., conscious reinvestment) [
23]. As a consequence, setting a goal might initially hamper performance. However, it might improve in the long run as the intended action is repeatedly executed and therefore becomes more and more automatic (i.e., a practice effect), requiring less expenditure of conscious attention and cognitive resources.
In contrast, if-then planning is assumed to facilitate an earlier (or even immediate) automation of actions. This assumption rests on research showing that the "if (situation) - then (action)" format of plans makes the planned situation easier to recognize when it occurs [
24,
25] and automates the initiation of the planned action [
26,
27]. This automaticity has been explained in terms of a joint sensorimotor simulation of situation-action links involved in planning that facilitates later execution of actions when the situation is encountered [
28], akin to the sensorimotor simulation of actions in sports [
29]. Given that planning automates the execution of an action, more attentional and cognitive resources should remain for executing other actions required during the serves. Compared to goals, it can thus be expected that planning does initially have less detrimental effects on performance and thus leads to more rapid performance improvements.
To sum up, we examine whether and how conveying the self-control strategies of setting goals and making plans to athletes affects their service performance. This sheds novel light on the potential effects of self-control strategies on complex behaviors in naturalistic settings and might help athletes and trainers gauge the impact of these self-control strategies on performance. Specifically, we investigate aggregate effects on errors, velocity, and precision as objective indicators of performance, as well as the temporal development of these performance indicators immediately after setting a goal or making a plan. To this end, we conducted a pilot field study in which active beach volleyball players from four Swiss volleyball schools were recruited. Athletes performed two series of 15 serves with either a goal or a plan to improve certain actions after the first series. Besides objective performance indicators, we also assessed the coaches’ ratings of performance improvement.
4. Discussion
We investigated whether and how conveying the self-control strategies of setting goals (goal condition) and making plans (plan condition) to beach volleyball players affects their service performance. To this end, we measured performance (i.e., errors, velocity, and precision) in two subsequent series of serves. After the first series, athletes either set a goal or made a plan to improve their performance based on their coach’s correction instruction. Prior research suggested that both goals and plans should improve performance, although the effects of plans should be more immediate than those of goals due to their automatic nature and thus lead to better aggregate performance (i.e., performance averaged across the serves of the two series of serves). Our data lent only partial support to these hypotheses. We observed the expected initial drops in performance in the goal condition together with a subsequent improvement. However, a similar pattern of results emerged in the planning condition as well. Specifically, we observed an initially decreased aggregate precision in both the goal and the plan conditions during the second series of serves, reflecting a sizeable immediate drop in performance with subsequent recovery. A similar development was observed for velocity, albeit with a smaller drop and a more effective increase afterwards so that aggregate performance was not affected. The concurrent improvement of precision and velocity over time is in line with research showing that people tend to increase their movement velocity as a function of the precision that is required [
37]. Note that these decrements in performance cannot be explained by a lack of warm-up. Players engaged in a prolonged warm-up phase under the guidance of their coaches prior to the experiment and no performance changes emerged during the first series of serves. Finally, participants in the plan condition committed fewer errors in the first compared to the second series of serves. However, players in the plan condition also made fewer errors than players in the goal condition during the first series of serves—that is, before we conducted the goal and plan interventions. Accordingly, the observed performance decrement could reflect a regression to the mean, maybe resulting from a randomization failure. What speaks against this interpretation is the observation that the conditions did not differ regarding demographic variables or their experience in playing volleyball. However, we feel that this particular finding should be taken with a grain of salt. Taken together, the observed pattern of results suggests that conveying self-control strategies can hamper service performance.
4.1. Implications
This is an important finding for athletes and coaches because both goals and plans represent such fundamental forms of self-control that they are likely to be omnipresent in the sporting context (even though not necessarily as deliberately used strategies). Not only do athletes self-control their actions autonomously during training or competition, correction instructions from coaches and even subtle hints from teammates may trigger self-control in the form of goals or plans. It is thus important to know that correction instructions have no immediate beneficial effect on performance and can even hamper certain aspects of performance. We observed that performance decrements primarily pertained to a decrease in target precision that seemed to reflect initial adjustment costs with subsequent recovery. This indicates that correction instructions may be detrimental during a competition and may require some practice, even for experienced athletes. Contrary to the hypotheses derived from previous research, this practice time could not be eliminated or reduced by plans (versus goals) in the present study.
Our results further suggest that coaches might perceive the effects of goals and plans on their players’ performance as more positive than it seems warranted on the basis of objective performance indicators. There are several explanations for this finding; for instance, their ratings could be based on a positively biased perception of their own correction instructions. Alternatively, the coaches might have focused less on aggregate performance than on the development of performance over time, or maybe myopically on the performance of the single self-controlled motor action that the players focused on. We cannot address this question based on the data we collected. Still, our study suggests that there is a gap between the actual and the perceived effects of self-control interventions that is worth studying.
Although plans in many areas enable more effective and efficient self-control than goals [
16] and their effectiveness also appears plausible in the sports context [
38], the corresponding research has so far been sparse and yielded contradictory findings [
18]. On the one hand, it has been shown that plans can improve competitive performance in tennis [
39] and endurance in a physically demanding task [
40] compared to goals. On the other hand, there are findings according to which plans in a muscular endurance task do not bring any performance advantages and can even have a negative effect on perceptions of performance [
21,
35]. In the present study, too, no performance benefits could be identified from plans in comparison to goals. Our study thereby also adds to the literature on costs and benefits of plans in comparison to goals [
41] in a naturalistic sport setting with volleyballs serves as a complex behavior that is difficult to regulate.
One possible explanation for the failure to observe a difference between goals and plans comes from research in sport psychology on the acquisition of motor skills. This research has shown that motor skills can be learned better if the attention of the athletes is drawn to the results of the action (external focus) rather than to the performing of the action (internal focus) [
42,
43]. Consequently, the effectiveness of goals and plans may depend on where they draw athletes’ attention to. Some findings from research on plans generally support this assumption, albeit suggesting that plans can be
more effective than action goals if they have an internal focus on performing the action [
44], which seems to be the case in the field of motor actions as well [
45]. The existing literature thus points to potentially complex interactions between the content of goals and plans and their effectiveness in the context of sport. In the present research, we did not provide the content of the goals and plans but rather relied on the coaches’ correction instructions. While this has the advantage of tailoring goals and plans to the individual needs and weaknesses of each athlete in the specific situation, future research should explicitly investigate how goal and plan content—especially in terms of attentional focus—affect their effectiveness in sport.
4.2. Limitations
One could argue that the present study would have benefited from a control group without goals and plans. There is no doubt that a comparison with such a control group would have been desirable from an experimental point of view. However, we had limited access to volleyball players and even with the realized design no particularly large test power could be achieved. We thus had to make a judgment call and decided for two of the most commonly investigated self-control strategies [
17]. That said, it should also be pointed out that the present sample consists of young athletes with an average of four years of training experience who went through a warm-up phase prior to participating in the study. It is therefore implausible to assume that the changes in performance we observed between the first and the second series of serves merely reflect short-term changes in performance (i.e., unstable performance that might characterize novice players). This argument is especially corroborated by the finding that all three performance indicators were stable across the first series of serves (i.e., no changes occurred regarding errors, velocity, or precision during the corresponding 15 serves). Had the athletes’ performance been unstable, this should have led to changes already during these serves, such as a steady improvement due to further warm-up.
The focus of our present research was on rather immediate, short term-effects of self-control on performance. It would also have been interesting to observe performance over a longer period of time after the intervention. Specifically, our data showed a continuous improvement of precision and velocity throughout the second measurement period. It is not clear how long this trend would have continued and what performance asymptote the athletes might have achieved in further serves; even an eventual improvement cannot be ruled out. Yet, 15 serves can have a decisive impact on the outcome of a competitive game and our results are thus highly relevant for athletes and coaches—also because the first serve in the second series was objectively worst and might thus undermine the coach’s intention to attain immediate improvement at crucial points of a game. A further interesting question pertains to whether goals and plans could have had a stronger impact on performance with a more extensive intervention. We focused on a single action and participants specified a single goal or plan to improve it. In comparison, many other psychological interventions in sport involve comprehensive programs that may last up to several weeks (e.g., self-talk interventions) [
46]. This makes it all the more noteworthy how directly goals and plans in the present study affected performance, and it opens up the possibility that conveying self-control strategies for regulating various service-related actions might be a viable alternative to our short intervention.
Another potential route for future research would be to focus on the (perceived) difficulty of performing the motor action that athletes want to control. For instance, it is well-known that the effects of goal and implementation intentions on goal attainment are similar for easy tasks [
27], and the failure to observe differences between conditions might results from such an easy task. On the other hand, strong feelings of self-efficacy are crucial for the effectiveness implementation intentions in difficult tasks [
47]. Accordingly, one might argue that the present results could in part be explained by insufficient feelings of self-efficacy. Although it seems unlikely that coaches gave correction instructions that were excessively easy or difficult, we cannot rule out that (perceived) task difficulty might explain the present results at least partly.
Finally, future studies might also add more direct measures of the intended or planned behaviors. In our study, for instance, tightening the hand or adjusting stride length in line with the goal or plan might not necessarily have resulted in better objective service performance. This should only be the case if there is a strong relationship between the identified behavior and the objective outcome measures. Our finding that the coaches’ positive assessment of performance development was not reflected in the objective indicators could be taken as an indication for the lack of such a relationship. Furthermore, our focus in the present studies was on framing the coaches’ correction instructions either as goals or plans. While this setup probably best reflects how these instructions are typically conveyed in applied settings, it does not constitute the most powerful intervention study on the effects of goal versus plans [
17,
18]. Such an intervention study should let all participants set the same goal explicitly in a first step (e.g., to perform a specified behavior) and then instruct participants in the plan condition to generate an if-then plan on top of that.