Armin Paravlic

Motor Imagery during Action Observation of Locomotor Tasks Improves Rehabilitation Outcome in Older Adults after Total Hip Arthroplasty

This study aimed at determining whether the combination of action observation and motor imagery (AO + MI) of locomotor tasks could positively affect rehabilitation outcome after hip replacement surgery. Of initially 405 screened participants, 21 were randomly split into intervention group (N = 10; mean age = 64 y; AO + MI of locomotor tasks: 30 min/day in the hospital, then 3×/week in their homes for two months) and control group (N = 11, mean age = 63 y, active controls). The functional outcomes (Timed Up and Go, TUG; Four Step Square Test, FSST; and single- and dual-task gait and postural control) were measured before (PRE) and 2 months after surgery (POST). Significant interactions indicated better rehabilitation outcome for the intervention group as compared to the control group: at POST, the intervention group revealed faster TUG (p = 0.042), FSST (p = 0.004), and dual-task fast-paced gait speed (p = 0.022), reduced swing-time variability (p = 0.005), and enhanced cognitive performance during dual tasks while walking or balancing (p < 0.05). In contrast, no changes were observed for body sway parameters (p ≥ 0.229). These results demonstrate that AO + MI is efficient to improve motor-cognitive performance after hip surgery. Moreover, only parameters associated with locomotor activities improved whereas balance skills that were not part of the AO + MI intervention were not affected, demonstrating the specificity of training intervention. Overall, utilizing AO + MI during rehabilitation is advised, especially when physical practice is limited.

Psychosocial predictors and psychological prevention of soccer injuries: A systematic review and meta-analysis of the literature

OBJECTIVES To examine (a) the relationships between the psychosocial risk factors and injury rates and (b) the effects of psychological-based prevention interventions on the injury risk of soccer players. DESIGN Scholarly electronic databases (PubMed/MEDLINE, Google Scholar, Scopus) were searched on 1 January 2017, complemented by manual searches of bibliographies. SETTING Systematic review and meta-analysis. PARTICIPANTS We identified 13 eligible studies, including a total of 1149 injured soccer players aged between 14 and 36 years. MAIN OUTCOME MEASURES Psychosocial risk factors, psychological-based prevention interventions and injury risk in soccer players. RESULTS Personality traits, such as trait anxiety and perceived mastery climate, along with a history of stressors, like negative-life-event stress or high level of life stress, daily hassle, and previous injury, are the main predictors of injury rates among soccer players. Also, from injury prevention studies, it has been shown that psychological-based interventions reduce injury rates (effect size = 0.96; 95% CI 0.34-1.58; p = 0.002) in senior soccer players. CONCLUSIONS Practitioners need to ensure injured soccer players are psychologically and socially ready to play. They should also employ psychological-based interventions (i.e., mindfulness, imagery, self-talk, stress management, relaxation, goal setting) when designing injury prevention programs.

A Meta-Analysis to Determine Strength Training Related Dose-Response Relationships for Lower-Limb Muscle Power Development in Young Athletes

It is well-documented that strength training (ST) improves measures of muscle strength in young athletes. Less is known on transfer effects of ST on proxies of muscle power and the underlying dose-response relationships. The objectives of this meta-analysis were to quantify the effects of ST on lower limb muscle power in young athletes and to provide dose-response relationships for ST modalities such as frequency, intensity, and volume. A systematic literature search of electronic databases identified 895 records. Studies were eligible for inclusion if (i) healthy trained children (girls aged 6–11 y, boys aged 6–13 y) or adolescents (girls aged 12–18 y, boys aged 14–18 y) were examined, (ii) ST was compared with an active control, and (iii) at least one proxy of muscle power [squat jump (SJ) and countermovement jump height (CMJ)] was reported. Weighted mean standardized mean differences (SMDwm) between subjects were calculated. Based on the findings from 15 statistically aggregated studies, ST produced significant but small effects on CMJ height (SMDwm = 0.65; 95% CI 0.34–0.96) and moderate effects on SJ height (SMDwm = 0.80; 95% CI 0.23–1.37). The sub-analyses revealed that the moderating variable expertise level (CMJ height: p = 0.06; SJ height: N/A) did not significantly influence ST-related effects on proxies of muscle power. “Age” and “sex” moderated ST effects on SJ (p = 0.005) and CMJ height (p = 0.03), respectively. With regard to the dose-response relationships, findings from the meta-regression showed that none of the included training modalities predicted ST effects on CMJ height. For SJ height, the meta-regression indicated that the training modality “training duration” significantly predicted the observed gains (p = 0.02), with longer training durations (>8 weeks) showing larger improvements. This meta-analysis clearly proved the general effectiveness of ST on lower-limb muscle power in young athletes, irrespective of the moderating variables. Dose-response analyses revealed that longer training durations (>8 weeks) are more effective to improve SJ height. No such training modalities were found for CMJ height. Thus, there appear to be other training modalities besides the ones that were included in our analyses that may have an effect on SJ and particularly CMJ height. ST monitoring through rating of perceived exertion, movement velocity or force-velocity profile could be promising monitoring tools for lower-limb muscle power development in young athletes.

Hormonal responses to striking combat sports competition:a systematic review and meta-analysis

Striking combat sports are challenging, commonly stressing the endocrinological system based on a mixture of body-contact actions and physiological efforts. The aims of this systematic review and meta-analysis were to discuss the hormonal responses related to striking combat sports competitions and to investigate the moderator and mediator variables of the hormonal response-competition/outcome relationship. Three electronic databases (i.e., PubMed, Google Scholar and ScienceDirect) were systematically searched (up to February 2016) followed by a manual search of retrieved papers. The data showed a moderate increase in cortisol (C) (ES = 0.79; 95% CI 0.31–1.28; p = 0.001), an extremely large increase in adrenaline (ES = 4.22; 95% CI 2.62–5.82; p < 0.001), and a very large increase in noradrenaline (ES = 3.40; 95% CI 1.03–5.76; p = 0.005) and human growth hormone (HGH) levels (ES = 3.69; 95% CI 1.96–5.42; p < 0.001) immediately following the combat events, compared to the control condition i.e., “pre-combat”. Furthermore, amateur athletes had a larger increase in C levels compared to highly trained athletes (ES = 2.91 [very large] vs ES = 0.56 [small]), while evening events showed greater alterations in C levels compared to morning events (ES = 1.91 [large] vs ES = 0.48 [small]), without significant differences between them (p = 0.26 and p = 0.06, respectively). The present meta-analysis also showed a small, insignificant increase in testosterone (T) (ES = 0.47 [small]; 95% CI -0.45–0.99; p = 0.074) and a decrease in insulin-like growth factor 1 levels (ES = -0.20 [trivial]; 95% CI -0.78–0.37; p = 0.486) immediately following the combat events, compared to the control condition. The type of combat sports practised, participants’ gender, and the nature of competition contests (i.e., official vs simulation) did not moderate the relationship between competition and hormonal response. Additionaly, sub-analysis results showed a significant difference between younger and older athletes (Q = 4.05, p = 0.044), suggesting that after combat, younger individuals (less than 17 years of age) had a small decrease in T levels (ES = -0.58), compared with the moderate increase observed in older individuals (ES = 0.76). In conclusion, irrespective of striking combat sports types, the results showed that both official and simulated bouts are a real stressor of the hormonal system of practitioners. Coaches and applied practitioners should adopt “pre-competitive cognitive/coping strategies” to improve the psychological state that mediates the hormonal changes-competition/outcome relationship of their athletes in order to mitigate athletes’ stress.

Data concerning the effect of plyometric training on jump performance in soccer players: A meta-analysis

Plyometric training (PT) enhances soccer performance, particularly vertical jump. However, the effectiveness of PT depends on various factors. A systematic search of the research literature was conducted for randomized controlled trials (RCTs) studying the effects of PT on countermovement jump (CMJ) height in soccer players. Ten studies were obtained through manual and electronic journal searches (up to April 2017). Significant differences were observed when compared: (1) PT group vs. control group (ES=0.85; 95% CI 0.47–1.23; I2=68.71%; p<0.001), (2) male vs. female soccer players (Q=4.52; p=0.033), (3) amateur vs. high-level players (Q=6.56; p=0.010), (4) single session volume (<120 jumps vs. ≥120 jumps; Q=6.12, p=0.013), (5) rest between repetitions (5 s vs. 10 s vs. 15 s vs. 30 s; Q=19.10, p<0.001), (6) rest between sets (30 s vs. 60 s vs. 90 s vs. 120 s vs. 240 s; Q=19.83, p=0.001) and (7) and overall training volume (low: <1600 jumps vs. high: ≥1600 jumps; Q=5.08, p=0.024). PT is an effective form of training to improve vertical jump performance (i.e., CMJ) in soccer players. The benefits of PT on CMJ performance are greater for interventions of longer rest interval between repetitions (30 s) and sets (240 s) with higher volume of more than 120 jumps per session and 1600 jumps in total. Gender and competitive level differences should be considered when planning PT programs in soccer players.