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Effect of motor imagery on enjoyment in knee-injury prevention and rehabilitation training: A randomized crossover study

Open AccessPublished:September 10, 2020DOI:https://doi.org/10.1016/j.jsams.2020.09.004

      Abstract

      Objectives

      The novel MOTor Imagery to Facilitate Sensorimotor Re-Learning (MOTIFS) model takes a uniquely holistic approach by integrating mental and physical aspects into current training programs. The aim of this trial was to evaluate enjoyment of MOTIFS training as compared to Care-as-Usual (CaU) knee injury and/or rehabilitation training. The primary hypothesis was that enjoyment would be greater following MOTIFS training than CaU training.

      Design

      Block-randomized 2 × 2 cross-over trial.

      Methods

      Thirty athletes (18−31 years, 50% women) currently or previously active in team ball sports, with no pain or injury preventing jump and/or directional changes. MOTIFS training integrates sport-specific experiences and equipment into physical exercises to increase individualized realism and meaning. The CaU condition included solely physical exercise. The main outcome was the Physical Activity Enjoyment Scale (PACES). Secondary outcomes included Self-Assessment Manikin (SAM; subscales Valence, Arousal, Dominance), Perceived exertion, pulse, duration, and movement quality.

      Results

      PACES scores were better following MOTIFS training than CaU (point estimate 24.67; 95% CI: 19.0; 30.3). Between-groups differences in SAM Valence (median 2, quartiles 1;3), Arousal (median 1, quartiles 0;2.25), and Dominance (median 0.5, quartiles 0;2), and RPE (median 1, quartiles −0.3;2), training duration (mean 5.34, 95% CI: −0.17; −0.73), and pulse (median 7.50, quartiles 0.25;16.75) were higher following MOTIFS training than CaU training.

      Conclusions

      Results suggest that the MOTIFS model, which integrates simultaneous physical and psychological interventions, is a clinically plausible method of influencing enjoyment and other psychological outcomes. Further studies may explore effects of the MOTIFS principles on injury prevention and rehabilitation training.

      Keywords

      Practical implications

      • Holistically integrating physical and psychological aspects into injury prevention and rehabilitation training is a plausible method of influencing patient-reported outcomes.
      • The MOTIFS model can be used by practitioners through athlete discussions to simultaneously physically and psychologically simulate individually relevant scenarios, involving athletes in decision-making and exercise design.
      • Integrating dynamic motor imagery uses sport-specific equipment, expertise and goals to create a single training exercise which enhances enjoyment while focusing on maintaining movement quality.

      1. Introduction

      Sports injury prevention
      • Gagnier J.J.
      • Morgenstern H.
      • Chess L.
      Interventions designed to prevent anterior cruciate ligament injuries in adolescents and adults: a systematic review and meta-analysis.
      and rehabilitation
      • Filbay S.R.
      • Grindem H.
      Evidence-based recommendations for the management of anterior cruciate ligament (ACL) rupture.
      programs focus mainly on physical training to improve neuromuscular strength and functional movement. Psychological factors such as motivation and satisfaction are important for return to sport following knee injury,
      • Sonesson S.
      • Kvist J.
      • Ardern C.
      • et al.
      Psychological factors are important to return to pre-injury sport activity after anterior cruciate ligament reconstruction: expect and motivate to satisfy.
      and stress reduction interventions
      • Gledhill A.
      • Forsdyke D.
      • Murray E.
      Psychological interventions used to reduce sports injuries: a systematic review of real-world effectiveness.
      aid in injury prevention. This has led to recommendations that psychological factors be addressed in knee-injury treatment,
      • Filbay S.R.
      • Grindem H.
      Evidence-based recommendations for the management of anterior cruciate ligament (ACL) rupture.
      with evidence also suggesting their importance in injury prevention program planning.
      • Ageberg E.
      • Bunke S.
      • Lucander K.
      • et al.
      Facilitators to support the implementation of injury prevention training in youth handball: a concept mapping approach.
      However, structured psychological training interventions are uncommon in knee injury prevention
      • Gledhill A.
      • Forsdyke D.
      • Murray E.
      Psychological interventions used to reduce sports injuries: a systematic review of real-world effectiveness.
      and rehabilitation
      • Coronado R.A.
      • Bird M.L.
      • Van Hoy E.E.
      • et al.
      Do psychosocial interventions improve rehabilitation outcomes after anterior cruciate ligament reconstruction? A systematic review.
      literature.
      Increasing focus on psychological strategies may promote participation
      • Jekauc D.
      Enjoyment during exercise mediates the effects of an intervention on exercise adherence.
      and motor learning,
      • Wulf G.
      • Lewthwaite R.
      Optimizing performance through intrinsic motivation and attention for learning: the OPTIMAL theory of motor learning.
      improving injury prevention and rehabilitation outcomes. Psychological skills training encompasses strategies aiming to influence performance, enjoyment, and motivation in athletic populations using strategies including arousal regulation, goal setting, and imagery.
      • Weinberg R.S.
      • Gould D.
      Introduction to psychological skills training.
      According to self-determination theory, motivation is derived from autonomy in decision-making, task-related competence, and interaction with others.
      • Deci E.L.
      • Ryan R.M.
      The’ what’ and’ why’ of goal pursuits: human needs and the self-determination of behavior.
      A systematic review shows that self-determined motivation encourages exercise and physical activity behaviors,
      • Teixeira P.J.
      • Carraça E.V.
      • Markland D.
      • et al.
      Exercise, physical activity, and self-determination theory: a systematic review.
      suggesting a need for interventions in which an athlete creates his or her own meaning to maximize psychological benefits.
      Imagery has been shown to enhance performance
      • Slimani M.
      • Bragazzi N.L.
      • Tod D.
      • et al.
      Do cognitive training strategies improve motor and positive psychological skills development in soccer players? Insights from a systematic review.
      using one’s own memories and experiences to create mental images of individualized and realistic situations with little to no movement. ‘Motor imagery’ focuses on contextual and kinesthetic aspects. Performed while sitting or standing still, this is known as ‘static imagery,’ but when done while simultaneously executing part or all of the movement, is termed Dynamic Motor Imagery (DMI).
      • Guillot A.
      • Moschberger K.
      • Collet C.
      Coupling movement with imagery as a new perspective for motor imagery practice.
      Integrating DMI into physical exercises is a potential method of addressing the lack of psychological focus in knee injury prevention and rehabilitation training. We have developed a novel training model, MOTor Imagery to Facilitate Sensorimotor Relearning (MOTIFS), which integrates individualized DMI into physical training to create a mental image of a scenario while simultaneously simulating motor and physical aspects. Using a MOTIFS intervention to create relevance may increase meaning and enjoyment of physical training exercises.
      The aim of this randomized cross-over trial is to explore the effect of a MOTIFS intervention on enjoyment of physical activity, as well as other patient-reported outcomes.
      The primary hypothesis is that athletes will report higher self-reported enjoyment of physical activity following MOTIFS training compared with a training session using established knee injury prevention and rehabilitation training principles. Secondary hypotheses are that athletes will report (i) more positive psychological states, and (ii) higher perceived exertion following the MOTIFS training.

      2. Methods

      This study utilized a block-randomized 2 × 2 cross-over design with a 10-min wash-out period to reduce the risk of confounding factors such as experience or fitness level. Ethical approval was provided by the regional ethical review board of southern Sweden (Etikprövningsnämnden [EPN]; DNR 2018/161; 2019/03154).
      Athletes 18–35 years old, currently (minimum of one year experience) or previously (within the last five years) active in competitive basketball, floorball, soccer, and/or handball were eligible for inclusion. Participants were excluded if they had any pain, injury, or problems hindering the ability to perform hop and/or directional change movements. Only uninjured participants were included to allow for evaluation of training itself, independent of the effect of injuries.
      Thirty participants were included (Table 1); testing was performed by n = 32 with one pilot participant, and one excluded due to a pre-existing injury. Participants were recruited from sports clubs and university programs in southern Sweden between June 2018 and June 2019. Those meeting age requirements were contacted for eligibility screening and invited to participate if eligible. Prior to testing at the university lab, the test-leader (NC) randomly assigned participants a training sequence (AB|BA, n = 15 in each sequence) using the randomization module available from the REDCap electronic data capture tool
      • Harris P.A.
      • Taylor R.
      • Thielke R.
      • et al.
      Research electronic data capture (REDCap)—a metadata-driven methodology and workflow process for providing translational research informatics support.
      hosted by Lund University. Due to the nature of the intervention, neither participants nor test-leader were blinded.
      Table 1Participant demographics (n = 30).
      VariableValue
      Gender15 Female (50%)
      Age (SD)22 (3.2) years
      BMI (SD)23.85 (2.91)
      Active (#)24
       Years’ experience (SD)13.8 (4.0)
      Inactive (#)6
       Years since active (SD)2.8 (1.9)
      Previous injury (#)23
       Time since injury (SD)41.0(35.3) mo
      SD = standard deviation; BMI = Body Mass Index (kg/m2); mo = months; Active = currently active with at least 1 year experience; Inactive = currently inactive, but have been active within the last 5 years; Previous Injury = self-reported experience of injury in the past that does not currently affect the ability to perform jump and/or directional change movements.
      The approximately 60-min testing occasion began with written and verbal information, informed consent, demographic information, a 2-min baseline pulse measurement, and a 5-min stationary bicycle warm-up. The first training session was completed, followed by self-report questionnaires, and a 10-min wash-out period. The testing occasion continued with the next assigned training condition, ending upon completing the questionnaires a second time.
      The training protocol was developed by the research team, consisting of experts in physical therapy and sports medicine (EA), sport psychology (NC, SG), and a clinically active physical therapist with a master’s degree and 10 years of clinical experience (GN). Upon finalizing the protocol, the test-leader (NC) assessed three participants under the supervision of an experienced physical therapist (GN) to ensure proper instruction and judgement of correct movement execution; n = 16 participants were filmed and evaluated for movement quality to further confirm this.
      Physical tasks were based on neuromuscular training principles aiming to improve sensorimotor control and achieve compensatory functional stability in people with knee injury.
      • Filbay S.R.
      • Grindem H.
      Evidence-based recommendations for the management of anterior cruciate ligament (ACL) rupture.
      Four tasks were completed on a self-reported preferred leg: toe-raise, single-leg standing, and single-leg squat movements, and a complex task including a dynamic directional change movement (Fig. 1). Participants were given verbal instructions and were allowed 3 warm-up repetitions. Support (a wooden dowel) was available if necessary to maintain movement quality.
      Fig. 1
      Fig. 1Explanation of physical exercise principles, and examples of use in CaU and MOTIFS conditions; All sets followed by a 45 s rest period.
      s = Seconds.
      Participant Flow Diagram uploaded as separate file
      Exercises in the Care-as-Usual (CaU) condition followed standard physical therapy practices (Fig. 1). Focus was on correct movement execution, with no specific effort to relate the movement to the participants’ sport.
      The MOTIFS condition consisted of sport-specific DMI integrated into CaU exercises to create a single holistic exercise. Individually relevant and meaningful exercises were designed by discussing CaU movements, with particular focus on relating them to individually relevant sport-specific movements. The mental image of the movement scenario was a main focus, examples of which may include imaging a specific opponent (“who are you dribbling past?”), where the shot or pass would be aimed (“top corner or teammates feet?”), and/or an important moment (final seconds of a game). Equipment, such as a ball, was used to maximize realism, as well as posters of each sport’s goal. The scenario was simulated, both psychologically and physically, resulting in a movement that may include a soccer player performing a toe-raise while simultaneously physically and psychologically simulating heading a ball, imaging where to aim the shot based on experiences of a specific goalie (Fig. 1; MOTIFS Explanation Film [online only Supplementary material]). Following the first set, participants were encouraged to optimize realism, for example by simulating pushing away an opponent before going up to reach for the header. The principles of the MOTIFS model allow participants to design relevant and meaningful movements adhering to physical exercise requirements (i.e. proper movement quality was maintained) throughout the session.
      The main outcome was the Physical Activity Enjoyment Scale (PACES), a valid 18-item self-report questionnaire on a 7-point Likert scale, presented as a total score from 18 (worst) to 126 (best).
      • Kendzierski D.
      • DeCarlo K.J.
      Physical activity enjoyment scale: two validation studies.
      Previous studies indicate that a difference of approximately 7 points is clinically relevant.
      • Jekauc D.
      Enjoyment during exercise mediates the effects of an intervention on exercise adherence.
      As the PACES questionnaire was not available in Swedish, the authors (NC, SG, EA) translated according to established guidelines,
      • Beaton D.E.
      • Bombardier C.
      • Guillemin F.
      • et al.
      Guidelines for the process of cross-cultural adaptation of self-report measures.
      and evaluated test-retest reliability using a separate sample of n = 30 university students, showing moderate reliability (ICC = 0.60; SEM = 6.50).
      The Self-Assessment Manikin (SAM) is a three-item self-report measure of emotional valence (positive or negative), arousal, and control using a 9-point Likert-type scale, each analyzed individually.
      • Bradley M.M.
      • Lang P.J.
      Measuring emotion: the self-assessment manikin and the semantic differential.
      Borg’s scale of perceived exertion measures rate of perceived exertion (RPE) from 6 (lowest) – 20 (highest).
      • Borg G.
      Borg’s perceived exertion and pain scales.
      Pulse data was collected via a Polar H10 (Polar Electro Oy, Inc., Kempele, Finland) pulse sensor connected to the freely available Polar Beat smartphone application throughout each training session, providing duration, and mean and maximum pulse data. Mean baseline pulse was calculated from the first minute of each session, during instructions.
      A sub-group of convenience participants, beginning after 10 were tested, were filmed from a front and side view during the toe-off movement to evaluate ability to maintain the same level of movement quality throughout both training sessions. As injury prevention and rehabilitation training focuses on movement quality,
      • Gagnier J.J.
      • Morgenstern H.
      • Chess L.
      Interventions designed to prevent anterior cruciate ligament injuries in adolescents and adults: a systematic review and meta-analysis.
      • Filbay S.R.
      • Grindem H.
      Evidence-based recommendations for the management of anterior cruciate ligament (ACL) rupture.
      it was deemed necessary to determine whether sport-specific movements in the MOTIFS training reduced movement quality as compared to CaU. Films were reviewed by a third party evaluator blinded to the purpose of the evaluation with 7 years of clinical experience as a physical therapist treating musculoskeletal disorders, in particular sports injuries. Films were scored from 0 (good) to 2 (poor) in four criteria: (i) overall clinical impression of the whole movement, then specifically (ii) plantar flexion, (iii) knee extension, and (iv) hip extension. A summed total score from 0 (best) to 8 (worst) was calculated in each condition. Unacceptable movement quality was defined as (i) individual criterion score exceeding one point difference between conditions, or (ii) more than two points total score difference in favor of CaU. This unvalidated scoring system was adapted from previously developed movement quality evaluation methods.
      • Nae J.
      • Creaby M.W.
      • Nilsson G.
      • et al.
      Measurement properties of a test battery to assess postural orientation during functional tasks in patients undergoing anterior cruciate ligament injury rehabilitation.
      • Crossley K.M.
      • Zhang W.-J.
      • Schache A.G.
      • et al.
      Performance on the single-leg squat task indicates hip abductor muscle function.
      It was decided upon as a pragmatic assessment by physical therapy experts with experience both clinically and in research.
      Based on a previous study in which exercises were completed focusing either on enjoyment or execution,
      • Jekauc D.
      Enjoyment during exercise mediates the effects of an intervention on exercise adherence.
      a sample-size estimation determined that n = 28 participants would be necessary to find a between-groups PACES score difference of 7 (SD 10) with a power of 0.8 and significance set at p < 0.05. A conservative estimate (larger SD than observed in Jekauc
      • Jekauc D.
      Enjoyment during exercise mediates the effects of an intervention on exercise adherence.
      ) was used due to lack of comparable interventional cross-over designs examining physical activity enjoyment.
      PACES, SAM, training duration, and RPE outcome data were available for 30 participants. Pulse data was available for n = 28 in the MOTIFS condition, and n = 29 in the CaU condition due to technical issues. Movement quality was evaluated for 18 participants, whereof n = 16 were included in the analysis due to technical issues.
      Following normality testing, treatment effects were tested using within-subjects, between-groups means for PACES and training duration using mixed models analyses in which period and treatment were used as fixed effects, and subject as a random effect. Duration was analyzed using a Log(10) transformation and by removing n = 1 outlier (longer training duration likely resulting from language difficulties during instructions) in order to fit the mixed model.
      SAM, RPE, mean and maximum pulse, and movement quality data were analyzed non-parametrically using Wilcoxon signed-rank testing. Significant results were checked for period and/or carry-over effects analyzed using Fisher’s Exact test. A paired-samples t-test compared baseline pulse means.
      Final analyses were performed using the IBM SPSS (v25) statistical software package according to a complete case analysis. Non-standardized effect sizes are reported as mean difference (parametric), and number of participants with improved scores (non-parametric).

      3. Results

      Mean PACES scores indicate higher enjoyment in the MOTIFS training than in the CaU training (mean difference 23.6, SD 15.1), with no significant period effect, independent of condition order (Table 2).
      Table 2Results of between-groups analyses of PACES, SAM, RPE, pulse, and Movement Quality scores.
      MOTIFSCare-as-usualDifference (MOTIFS minus CaU)
      nMean (SD)nMean (SD)nPoint Est. (SE)P95% CIPeriod (p; 95% CI)
      PACES30102.5 (9.3)3077.8 (18.1)3024.67 (2.77)<0.00119.0; 30.30.32 (-2.9; 8.5)
      nMedian (IQR)nMedian (IQR)nMedian (IQR)pFisher’s ExactImproved (%)No Diff (%)
      SAMVal308 (7;9)306 (5;7)302 (1;3)<0.0010.00025 (83)4 (13)
      SAMAr305 (5;7)305 (3;5)301 (0;2.25)0.0040.02516 (53)9 (30)
      SAMDom307 (5;8)305 (3;7)300.50 (0;2)0.0140.14315 (50)9 (30)
      RPE3013 (12;14.3)3012.5 (10;13.3)301 (-0.3;2)0.0100.02719 (63)4 (13)
      HRmean28101.92

      (96.1;108.6)
      2998.77

      (93.0;109.8)
      284.32

      (0.7;5.6)
      0.0050.00622 (79)0 (0)
      HRmax28144.50

      (130.8;152.5)
      29134.00

      (121.5;145.0)
      287.50

      (0.3;16.8)
      <0.0010.02121 (75)1 (4)
      MQTot154.0 (1;5)162.5 (1;4.75)150 (-2;1)0.856N/A5 (33)6 (40)
      MQOA161 (0;1)161 (0;2)160 (-1;0)0.248N/A3 (19)7 (44)
      MQPlant151 (1;2)161 (1;1)150 (0;1)0.480N/A5 (33)7 (47)
      MQKnee160 (0;1)160 (0;1)160 (0;0)0.739N/A3 (19)10 (63)
      MQHip160 (0;1)160 (0;1)160 (0;0)1.000N/A3 (19)10 (63)
      p = exact significance (2-tailed); significance set at p = 0.05; Fisher’s Exact (2-sided) significance set at p = 0.05.
      MOTIFS = MOTor Imagery to Facilitate Sensorimotor Re-learning; CaU = Care-as-Usual; SD = Standard Deviation; Point Est. = Point Estimate; SE = Standard Error; CI = Confidence Interval; Period = Period Effect; PACES = Physical Activity Enjoyment Scale; IQR = Interquartile Range; Improved = Number of participants with improved scores in MOTIFS compared to CAU condition; No Diff = Number of participants with no differences between MOTIFS and CaU conditions; SAM = Self-Assessment Manikin; SAMVal = SAM Valence subscale; SAMAr = SAM Arousal subscale; SAMDom = SAM Dominance subscale; RPE = Ratings of Perceived Exertion; HRmean = Pulse – mean beats per minute; HRmax = Pulse – maximum beats per minute; MQTot = Movement Quality Total Scores; N/A = Not applicable, test not performed due to non-significant Wilcoxon results; MQOA = Movement Quality Overall; MQPlant = Movement Quality Plantar Flexion; MQKnee = Movement Quality Knee Extension; MQHip = Movement Quality Hip Extension.
      Significant differences in all SAM items indicate more positive valence, higher arousal, and greater dominance following MOTIFS training (Table 2). There were no period effects for valence nor arousal. A non-significant Fisher’s Exact for dominance indicates a potential period effect.
      Perceived exertion and mean and maximum pulse were significantly higher following MOTIFS training than CaU training, with no significant period effects (Table 2). Baseline pulse was significantly higher in the first (98.24, SD 16.80) than in the second (92.74, SD 12.11) training session (5.12, SD 10.04, p = 0.012, 95% CI: 9.01;2.70), indicating a potential residual effect.
      The duration of the MOTIFS (19.47, SD 5.48) training was significantly longer than CaU (14.39, SD 3.69) training (mean difference 5.08, SD 5.42; point estimate = 0.12, SE = 0.02, p = 0.000; 95% CI: −0.07;0.17) with no period effects (p = 0.529; 95% CI −0.06;0.03).
      Movement quality scores for 13 (87%) participants were ‘acceptable.’ Unacceptable scores were due to one 2-point “Overall Impression” difference, one 3-point total score difference in favor of CaU training, and one missing individual item preventing reliable total score calculation. No individual items, nor total scores, were significantly different between conditions (Table 2).

      4. Discussion

      Results confirm the hypothesis that self-reported enjoyment of physical activity would be higher following MOTIFS training compared with CaU training. All secondary hypotheses were confirmed, indicating more positive valence, higher perceived arousal, and greater perceived dominance according to SAM, higher mean and maximum pulse, and higher perceived exertion following MOTIFS training. MOTIFS training duration was approximately 5 min (35%) longer than CaU.
      PACES scores were significantly higher in MOTIFS training than CaU training, constituting a clinically relevant difference (i.e. >7-point difference). Rehabilitation and injury prevention training typically focuses on functional execution of movements in reference to oneself,
      • Filbay S.R.
      • Grindem H.
      Evidence-based recommendations for the management of anterior cruciate ligament (ACL) rupture.
      known as an internal focus of attention. The MOTIFS model increases relevance by focusing on individualized and sport-specific meaning, shifting attention away from the body and more towards the task to be simulated, known as an external focus of attention.
      • Wulf G.
      • Lewthwaite R.
      Optimizing performance through intrinsic motivation and attention for learning: the OPTIMAL theory of motor learning.
      Athletes have reported a desire for this sport-specific focus in training programs,
      • Ageberg E.
      • Bunke S.
      • Lucander K.
      • et al.
      Facilitators to support the implementation of injury prevention training in youth handball: a concept mapping approach.
      • Donaldson A.
      • Callaghan A.
      • Bizzini M.
      • et al.
      A concept mapping approach to identifying the barriers to implementing an evidence-based sports injury prevention programme.
      and it may distract from discomfort or provide a pleasurable component,
      • Craike M.J.
      • Hibbins R.
      • Cuskelly G.
      The influence of various aspects of enjoyment on participation in leisure time physical activity.
      possibly explaining the higher enjoyment in MOTIFS training. Encouraging individualization and shared decision-making to create meaning may encourage enjoyment in future sessions through variation and progression.
      Understanding and application of knowledge has been suggested to be important for utilizing training strategies.
      • Ageberg E.
      • Bunke S.
      • Lucander K.
      • et al.
      Facilitators to support the implementation of injury prevention training in youth handball: a concept mapping approach.
      Increased focus on the meaning and relevance of exercises highlights practical application, possibly shifting motivation from extrinsic (outcome oriented) to intrinsic (inherent satisfaction).
      • Teixeira P.J.
      • Carraça E.V.
      • Markland D.
      • et al.
      Exercise, physical activity, and self-determination theory: a systematic review.
      Thus, exercises done with situation-specific external focus are likely more meaningful.
      • Wulf G.
      • Lewthwaite R.
      Optimizing performance through intrinsic motivation and attention for learning: the OPTIMAL theory of motor learning.
      The OPTIMAL theory of motor learning states that externally focused, correctly executed movements become automatic, allowing one to learn and improve functional movement.
      • Wulf G.
      • Lewthwaite R.
      Optimizing performance through intrinsic motivation and attention for learning: the OPTIMAL theory of motor learning.
      Our results suggest that MOTIFS training provides this external focus, allowing for quality execution of physical exercises.
      The MOTIFS model involves the athlete in creating simulations based on previous experiences of the movement. This supports the theory of re-investment, which states that working memory can be used to manipulate conscious knowledge, thereby disrupting motor execution.
      • Masters R.
      • Maxwell J.
      The theory of reinvestment.
      For example, focusing on the environment in a film-simulated running path improves running economy and kinematic movements more than concentrating on physical movement and technique.
      • Schücker L.
      • Parrington L.
      Thinking about your running movement makes you less efficient: attentional focus effects on running economy and kinematics.
      In MOTIFS training, familiarity with imaged situations creates more meaningful context than focusing solely on execution, possibly allowing for more automatized and efficient movements. Our results support this, as movement quality was not compromised during MOTIFS training, despite additional context-specific movements.
      More positive psychological responses and higher levels of arousal following MOTIFS training than CaU may be due to more meaningful context, which may positively influence psychological states (i.e. valence).
      • Wulf G.
      • Lewthwaite R.
      Optimizing performance through intrinsic motivation and attention for learning: the OPTIMAL theory of motor learning.
      It may be easier to recall emotions associated with personally relevant experiences, resulting in higher perceived arousal.
      • Gregg M.J.
      • Jenny O.
      • Hall C.R.
      Examining the relationship between athletes’ achievement goal orientation and ability to employ imagery.
      Participants reported feeling significantly more control over the situation (as opposed to feeling controlled) in MOTIFS training compared to CaU. A potential period effect, however, indicates that feelings of control may increase independent of training form; these results should therefore be interpreted with caution. Other possible explanations include that more focus on the athlete’s own expertise may increase feelings of control.
      • Wulf G.
      • Lewthwaite R.
      Optimizing performance through intrinsic motivation and attention for learning: the OPTIMAL theory of motor learning.
      In current rehabilitation programs, shared decision-making tends to limit itself to goals and broad treatment options,
      • Rose A.
      • Rosewilliam S.
      • Soundy A.
      Shared decision making within goal setting in rehabilitation settings: a systematic review.
      while the MOTIFS model specifically involves the athlete in exercise design.
      Mean pulse and perceived exertion were higher in the MOTIFS condition than in the CaU condition, though the difference may not be clinically relevant. Possible explanations include that integrating imagery uses additional muscle groups, creating more physically demanding situations, such as shooting a ball. Imagery itself has also been suggested to influence muscle activation, as ‘experts’ exhibit more neurological activation than beginners.
      • Olsson C.J.
      • Jonsson B.
      • Larsson A.
      • et al.
      Motor representations and practice affect brain systems underlying imagery: an FMRI study of internal imagery in novices and active high jumpers.
      Another possible explanation is that self-paced exercise may be more pleasurable than imposed or prescribed intensity, leading to lower psychological ‘costs’ and perceived exertion at similar intensity levels.
      • Ekkekakis P.
      Let them roam free?.
      The MOTIFS training took approximately 36% longer, likely due to athlete involvement in discussions to create relevance and meaning, rather than simply giving explicit instructions. The movements may also take more time due to additional contextual movements – a shot or pass for example. Emphasizing movement and skill recall may increase time needed to learn the new concept, in which case, duration in future sessions may be reduced. The observed duration is consistent with recommendations that imagery is effective at maximum 20 min.
      • Driskell J.E.
      • Copper C.
      • Moran A.
      Does mental practice enhance performance?.
      Strengths of this study include that it utilized a randomized cross-over design with predefined hypotheses. A novel and interdisciplinary training model was tested, in which psychological training is integrated into physical training, with proper execution confirmed by a blinded and independent third party. Results provide insight into potential improvements in physical training using a holistic approach focusing on physical and psychological factors important for knee injury prevention and rehabilitation.
      Limitations include that learning and/or carry-over effects cannot be ruled out. This risk is acceptable, as results will inform future studies. Longitudinal and residual effects analyses cannot be done, so future research may explore this. Blinding was impossible, as the test leader must be familiar with the MOTIFS model to effectively administer the training. The first author acted as test-leader, so bias cannot be ruled out.
      The MOTIFS model was designed for knee-injured people, but this study includes uninjured participants. This is acceptable, as principles of the model were evaluated, which can be adapted for use in both injury prevention and rehabilitation settings. The aim of this study was to examine effects of the MOTIFS model on self-reported outcomes, so future studies may also examine outcomes of physical function. An ongoing randomized controlled trial will examine the effects of a MOTIFS intervention on muscle function and psychological readiness to return to activity, among other objective variables in a knee-injured sample (clinicaltrials.gov identifier: NCT03473821).

      5. Conclusions

      The MOTIFS model is a plausible method of influencing patient-reported outcomes such as enjoyment using interdisciplinary and person-centered principles to integrate simultaneous psychological and physical training in knee injury prevention and rehabilitation programs. Integration of the MOTIFS principles into physical training is vital as a distinguishing factor compared to other studies, which apply separate physical and psychosocial interventions. Potential implications for self-efficacy
      • Wesch N.
      • Callow N.
      • Hall C.
      • et al.
      Imagery and self-efficacy in the injury context.
      and adherence
      • Craike M.J.
      • Hibbins R.
      • Cuskelly G.
      The influence of various aspects of enjoyment on participation in leisure time physical activity.
      warrant further studies to determine the efficacy of the MOTIFS model in injury prevention and rehabilitation training.

      Acknowledgements

      The authors would like to thank all participants in the study, as well as Axel Ström and Tommy Schyman for their statistical guidance, Camilla Holmqvist for her work in determining test-retest reliability of the PACES questionnaire translation, and August Estberger for evaluating movement quality films. This work was funded by Folksam insurance company , and the Swedish Research Council for Sport Science . Grants were also received from the Skåne Regional Council, Sweden , the Kocks Foundation, Sweden , the Swedish Rheumatism Association, Sweden , the Crafoord Foundation, Sweden , the Magnus Bergvall's Foundation, Sweden , and the Faculty of Medicine, Lund University, Sweden .

      Appendix A. Supplementary data

      The following are Supplementary data to this article:

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