Physical fitness is of great significance to athletes in both single-player and team sports. The countermovement jump (CMJ) is one of the most commonly applied jump tests for assessing the mechanical capacities of the lower extremities. The KForce Plates system is a portable force platform that sends action-time audio and visual biofeedback to a smartphone or tablet through the KForce application, making it a suitable instrument for assessing the CMJ. The aim of the present study was to evaluate the test–retest reliability and validity of the portable force platform (KForce Plates) in the evaluation of the CMJ in collegiate athletes compared to a validated application, My Jump 2. Thirty-four collegiate professional athletes, deriving from various sports backgrounds, participated in the present study. The CMJs were reported with the portable KForce Plates and the simultaneous use of the ‘My Jump 2’ application using an iPhone 13 between days 1 and 7. Our findings revealed high test–retest reliability (ICC = 1.00 and ICC = 0.99) in-between measurements. High correlations were monitored amongst the portable KForce plates and the My Jump 2 application for measuring the CMJ (r = 0.999, p = 0.001). The Bland–Altman plot exhibits the limits of agreement amongst the portable KForce plates and the My Jump 2 application, where the bulk of the data are within the 95% CIs with an agreement of ≈1 cm. Our findings suggest that the portable KForce Plates system is a reliable and valid instrument and, therefore, can be used by experts in the sports field.

This review evaluated the efficacy of Motor Imagery intervention in athletes with lower limb sports injuries that could affect their pain levels during rehabilitation. We carried out a thorough research of the scientific literature for RCT studies in athletes with lower limb musculoskeletal sports injuries including search terms Motor Imagery AND pain, Motor Imagery AND sport injuries, Motor Imagery AND lower limb. We searched 3 major databases, PubMed, Scopus, and ScienceDirect, with the search period ranging from their inception until May 2022. We assessed the quality of the studies using the PEDro Scale and the data was recorded and extracted with the use of Mendeley software. The search criteria resulted in a pool of 10.107 possible articles. Upon completion of the selection procedure, only 3 RCT studies met the inclusion criteria with a total of 60 injured athletes (n = 18 with ankle sprain and n = 42 with ACL injuries). The meta-analysis showed no statistically significant positive effects of MI intervention on pain intensity after lower limb sports injuries (n = 60; MD = −1.57; 95% CI: −3.60 to 0.46; I² = 50%; p = 0.13). The limited number of studies could justify the statistically insignificant effect of MI, but although the methodological quality of the studies was moderate to high, the heterogeneity of them was also relatively high. More RCT’s are required to explore the effect of MI on pain in athletes with lower limb injuries in order to address psychophysiological processes during rehabilitation.

Lateral ankle sprains are one of the most frequent athletic injuries in football, causing deficits in balance. Motor Imagery (MI) has been successively included in sports rehabilitation as a complementary therapeutic intervention. The aim of the present study was to explore the effects of MI on static and dynamic balance and on the fear of re-injury in professional football players with Grade II ankle sprains. Fifty-eight participants were randomly allocated into two groups: First—MI group (n = 29) and second—Placebo group (n = 29), and they each received six intervention sessions. The first MI group received MI guidance in addition to the balance training program, while the second Placebo group received only relaxation guidance. One-way ANOVA showed statistically significant results for all variables, both before and 4 weeks after the interventions for both groups. The t-test showed statistically significant differences between the two groups for static balance for the right lower extremity (t = 3.25, S (two-tailed) = 0.002, p < 0.05) and also for heart rate (final value) in all time phases. Further research is needed in order to establish MI interventions in sports trauma recovery using stronger MI treatments in combination with psychophysiological factors associated with sports rehabilitation.

The VMIQ-2 has been proven a valid and useful psychometric tool to measure the ability of vividness of movement imagery in sports. However, no validity study has been reported in Greek. The purpose of the present study was to examine the validity and reliability of the VMIQ-2 into Greek in adult athletes derived from various sports activities and different athletic levels. The VMIQ-2-GR (n = 160) was examined for translation, construct and discriminant validity, and also for internal consistency and test–retest reliability. CFA did not show acceptable global fit indices and only the index of (x²/df) showed an acceptable fit. The resulting factors of the EFA highlighted the discrepancy between the Greek version and the original version of the VMIQ-2. The results of the discriminant validity confirmed that the VMIQ-2-GR was well discriminated between subgroups of athletes and, therefore, showed a good discriminant validity. The Cronbach a coefficient was excellent at both measurements (> 0.92 in all cases for all factors). The Spearman rho correlation coefficients were statistically significant (< 0.001) with values > 0.47. The findings of the VMIQ-2–GR suggest that it is a valid and reliable tool and it can be used by sports psychologists, sports physiotherapists, coaches and researchers who aim to apply MI in the Greek athletic population.

Lateral elbow tendinopathy (LET) is a common upper limb pathology in people involved in manual occupations. The upper extremity functional index (UEFI) was specifically designed to evaluate functional limitations in patients with upper limb pathology. The UEFI was developed in English and has been translated into several languages, including Greek. However, it has been assessed only in patients with shoulder pathology. Thus, the aim of this study was to pilot-test the Greek version of the UEFI (GV-UEFI) questionnaire and assess its measurement properties in patients with LET. Thirty patients with LET were recruited and asked to fill in the GV-UEFI twice and the disabilities of arm, shoulder, and hand questionnaire (DASH) once. The internal consistency and test–retest reliability were examined using Cronbach’s alpha and the intraclass correlation coefficient (ICC). The standard error of measurement (SEM) and the minimum detectable change (MDC) were calculated and possible ground or ceiling effects were also examined. Convergent validity was evaluated with the Greek DASH using Pearson’s correlation. Lastly, the unidimensionality of the scale was examined through principal component analysis to verify construct validity. Internal consistency was high for the GV-UEFI (Cronbach’s a = 0.98) and test–retest reliability was excellent (ICC = 0.98). The SEM was 2.95 and the MDC was 6.85. Test–retest reliability of each item was good (ICC > 0.87). The correlation analysis demonstrated a strong correlation between the GV-UEFI and the DASH. No floor or ceiling effects were found. Principal component analysis verified the construct validity and the unidimensionality of the scale. The GV-UEFI was successfully tested in patients with LET. It seems that the GV-UEFI can be used reliably in Greek-speaking patients with LET. However, the measurement properties of this scale should be examined in a larger sample of LET patients.