Itoh, Sho (2020) Effect of imagery dose variables on performance in sport. PhD thesis, Victoria University.

Abstract

The main aim of this thesis was to examine the imagery dose-response relationship of three key imagery dose variables to sport performance. Morris et al. (2012) proposed that key imagery dose variables of imagery repetitions, duration, and frequency are related to imagery effectiveness in the sport context. They explained that the number of imagery task repetitions in a session, duration of imagery sessions, and frequency of imagery sessions in a week can be defined as “imagery dose variables” that are incorporated in imagery training design. However, researchers have not examined these imagery variables systematically, so that sport imagery training interventions have involved widely varying doses of repetitions, duration, and frequency of sessions (Paravlic et al., 2018; Schuster et al., 2011). Thus, it is important to examine whether each key imagery dose variable has an independent effect on sport performance. To examine this question systematically, I used the same research design across all three studies, following the proposal by Morris et al. (2012). I systematically varied one imagery dose variable, holding the other two imagery dose variables constant. In addition, I employed the same task, basketball free-throw shooting (FTS), and similar, moderate skill-level participants in all three studies. In Study 1, I examined the effect of three different numbers of imagery task repetitions in an imagery session on FTS performance, holding the imagery duration and frequency dose variables constant. I randomly allocated 36 male participants (Mage = 25.17, SD = 4.26) into four conditions, namely 10-repetitions, 20-repetitions, 30-repetitions, and Control conditions. I assessed imagery ability in participants using the Sport Imagery Ability Measure (SIAM) to ensure participants had at least moderate imagery ability (Watt, Klep, & Morris, 2018; Watt, Morris, & Andersen, 2004a). I checked that all participants had moderate FTS performance. The FTS test comprised two sets of 20 FTS with 2-minute rest interval between sets. I measured shooting accuracy using a scoring system that awarded 3 points for a clean basket, 2 for the ball going in the basket off the ring, 1 for the ball missing the basket off the ring, and 0 for the ball completely missing the basket. I tested FTS at pre-test, and after the final imagery session in Weeks 1, 2, 3, post-test (Week 4), and retention test (Week 5). In the imagery training phase, imagery condition participants undertook the imagery training program for 12 sessions (three times a week over four weeks). Results showed that the 20-repetition condition had the highest FTS mean at post-test, which was significantly higher than the Control condition. In Study 2, I varied imagery training session durations and examined the effect on FTS performance, while holding repetitions constant, based on the most effective number of repetitions in Study 1, and frequency of sessions per week constant at the same level as in Study 1. I randomly distributed 36 male basketball players (Mage = 25.17, SD = 4.26) into four conditions, namely 8-minute imagery session duration, 13-minute imagery session duration, 18- minute imagery session duration, and Control conditions. Results showed that the 13-minute duration condition had the highest FTS means at post-test and retention test between research conditions and had a significantly higher FTS mean than the Control condition at post-test. In Study 3, I tested the effects of different frequencies of imagery training sessions in a week on FTS performance, and I held constant the most effective imagery repetitions and duration of sessions from Studies 1 and 2, respectively. I randomly allocated 40 male basketball players (Mage = 20.92, SD = 3.01) into four conditions, namely 3 imagery sessions per week, 4 imagery sessions per week, 5 imagery sessions per week, and Control conditions. The 4 imagery sessions per week condition had the highest FTS means at post-test and retention test, and its FTS means were significantly higher than the Control condition at post-test and retention test. To conclude the thesis findings indicated that the most effective imagery dosages in three different dosages of each dose variable tested were 20 imagery task repetitions, imagery session duration of 13 minutes, and 4 imagery sessions per week. Also, all three imagery doses in each study showed substantial effects on performance compared to the no-imagery Control condition. I found positive results in each study suggesting that the new imagery dose-response protocol represents an appropriate research design. The findings in this thesis also provide guidelines for researchers to implement replication studies in terms of examining the three imagery dose variables together in imagery training programs. Thus, the present thesis reflects a high degree of originality in research on imagery training, and it contributed valuable new knowledge about the relative effectiveness of imagery training contexts.

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