A Comparison of Different Strength Measurement in Taekwondo: Herman Trainer, Manual Tester, and Standing Long Jump

Background and Objective: The accurate prediction of strength development relies on identifying the most appropriate measurement methods. This study compared diverse strength measurement techniques to assess their effectiveness in predicting strength development. Participants were taekwondo athletes competing at the red-black belt level or above. Methods: Technical striking forces (palding, dollyeo chagi, dwit chagi, and yeop chagi) were measured using a Herman Digital Trainer fixed to a striking stand. Quadriceps and hamstring strength were assessed with a Lafayette force measuring device. Explosive leg strength was evaluated through a standing long jump test, normalized for leg length. The Pearson correlation coefficient was used to examine relationships between measurement methods. Results: The standing long jump test showed no significant correlation with other strength assessments. A moderate positive correlation was found between Herman digital trainer measurements and Lafayette digital hand-held dynamometer results. A high positive correlation (r = 0.736, p < 0.001) emerged between hamstring strength and palding chagi technical strike force results. Technical strike kicks showed a significant positive correlation with each other and, also, a right foot-left foot correlation was observed. Conclusions: It was concluded that the standing long jump test, which was shown as one of the explosive leg strength measurement methods in field studies as an alternative to laboratory tests, did not correlate with other strength tests; therefore, this test is weak and insufficient to predict strength skills in taekwondo. In addition, this study showed that the hamstring muscle was more predictive in the measurement of technical strength. In future studies, it might be more useful to measure hamstring muscle strength or technical kick strength instead of a standing long jump field test.

Test-retest reliability and sensitivity of senior elite amateur boxers maximal punch force, as quantified by a vertically mounted force plate

An ecologically valid, reliable and sensitive method of quantifying punch force variables would be useful for coaches and practitioners monitoring combat-specific performance. The present study utilised a vertically mounted force plate to quantify the peak punch force and rate of force development (RFD) of amateur boxers. Ten male senior elite amateur boxers performed maximal jab, cross, and hook punches across two separate days. The force plate showed excellent within-day and good-to-excellent between-day reliability for peak punch impact force and RFD (ICC 0.89-0.99). The CV% for all punch force variables were similar on day 1 (3-9%) and day 2 (4-10%). Standard error of measurement (SEM) and smallest worthwhile changes (SWC) revealed the force plate can detect small-to-moderate changes in punch performance. The greatest impact forces and RFD were found in the rear hook (2624 ± 581 N, 296448 ± 101823 N.s-1), followed by the lead hook (2524 ± 532 N, 256813 ± 81735 N.s-1), cross 2425 ± 545 N, 193004 ± 62671 N.s-1) and jab (1645 ± 537 N, 116675 ± 41577 N.s-1). The vertically mounted force plate is a reliable and sensitive test of punch performance, thus may be useful in determining the efficacy of training interventions.

Biomechanics of the lead straight punch and related indexes between sanda fighters and boxers from the perspective of cross-border talent transfer

Objective: To bridge the technical gaps in reserve athletes in China's national boxing program and to rapidly improve the overall level of boxing, the Wushu Sports Administration Center of the General Administration of Sports of China has sent outstanding Sanda players to boxing events through cross-border talent transfer. This was done to widely improve the strengths and resources in various fields to prepare for the Tokyo Olympic Games. In view of this, we analyzed and compared differences in biomechanical parameters of the lead straight punch and index of force developments of the lower extremities between Sanda and boxing. The results provide information and insights to bridge the technical gaps in cross-border talent transfer from Sanda to boxing. Methods: We employed a Vicon infrared 3D motion capture system, two Kistler platforms, a Kistler target, and a synchronous instrument. Eleven boxers and sixteen Sanda athletes were recruited, and their lead straight punch techniques were compared and analyzed. Three indexes of punch velocity, six indexes of strength measurement, and four indexes of lower extremity strength were analyzed. Results: Significant differences in the peak punch velocity and contact velocity were found between the two groups. Furthermore, significant differences were noted in the peak impulse, peak strength, relative strength, and the rate of force development (RFD). Among the kinetics indexes of lower limbs, the front leg strength index was higher in the boxing group than in the Sanda group, namely the RFD index and RFD/body mass. Conclusion: Based on the disparity in the effects of the lead straight punch and biomechanical parameters of both lower extremities, we can conclude that, compared to the boxers, most Sanda athletes lack standard punching technique. Therefore, it is advised that coaches and practitioners carefully consider selecting Sanda athletes with higher technical standards of punching.

Biomechanics of the lead straight punch of different level boxers

We analyze and compare the differences in the biomechanical parameters between the lead straight punch and the index of force development of the lower extremities of boxers of different levels of ability. This can bridge the technical gap and provide insight and information for training strategies and athlete selection. To this end, a synchronized Vicon infrared 3D motion-capture system, two Kistler force platforms, and Kistler 8 target sensors were used for analysis. Sixteen boxers were recruited and sorted into an elite group (height 181.14 ± 3.01 cm, body mass 76.00 ± 10.028 kg) and a junior group (179.67 ± 5.84 cm, body mass 75.47 ± 12.19 kg), and their lead straight punch was then compared and analyzed. Three punch velocity indexes-peak velocity, contact velocity and Punching deceleration rate-six strength indexes-impulse, peak force, relative strength, peak time (frame), rate of force development (RFD), and movement time-and five exertion of both legs indexes- peak force, peak force/body mass, peak time, RFD index, and RFD/body mass index-were selected for analysis. Significant differences in the peak punch velocity and contact velocity were found between the two groups (7.162 ± 0.475 m•s^-1vs. 6.317 ± 0.415 m•s^-1, Cohen's d = 1.89, p < 0.01, 5.557 ± 0.606 m•s^-1 vs. 4.874 ± 0.385 m•s^-1, Cohen's d = 1.34, p < 0.05). Furthermore, significant differences were noted in the peak force [(1507.99 ± 411) N vs. (1035.45 ± 220) N, Cohen's d = 1.43, p < 0.01], relative strength [(21.04 ± 5.88) N•kg^-1 vs. (15.61 ± 2.53) N•kg^-1, Cohen's d = 1.19, p < 0.05], impulse [(88.61 ± 25.88) N•ms^-1 and (60.53 ± 9.03) N•ms^-1, Cohen's d = 1.45, p < 0.05], and RFD [(88.61 ± 25.88) N•ms^-1 and (60.53 ± 9.03) N•ms^-1, Cohen's d = 1.45, p < 0.05]. Among the four indexes of the lower extremities from two embedded Kistler force platforms, there were significant differences in the lead leg's peak force/body mass [(19.68 ± 4.096) N•kg^-1vs. (13.320 ± 2.223) N•kg^-1, t = 3.902, Cohen's d = 1.92, p < 0.01], RFD index [(16.90 ± 3.269) N•ms^-1vs. (10.28 ± 4.313) N•ms^-1, Cohen's d = 1.72, p < 0.01], and RFD/body mass index [(23.47 ± 4.09%) N•ms^-1Kg^-1 vs. (15.38 ± 5.65%) N•ms^-1Kg^-1, Cohen's d = 1.64, p < 0.01]. There were no significant differences in the four indexes on the rear leg between the two groups (p > 0.05). Based on the disparity in the effect of the lead straight punch and the biomechanical parameters of both lower extremities, the boxers must attach importance to sequential acceleration-braking training to improve the terminal velocity of the hand, and thus improve the contact velocity. Furthermore, it is advised that coaches and practitioners carefully consider increasing start-up strength training of the lead leg and attempt to improve the peak velocity of the lead straight punch. In addition, these biomechanical parameters can be used as criteria for the selection of boxers.

Performance Level and Strike Type during Ground and Pound Determine Impact Characteristics and Net Force Variability

The evaluation of strike impact is important for optimal training, conditioning and tactical use. Therefore, the aim of this study was to evaluate ground and pound strikes, in terms of net force variability, across genders and performance levels. Eighty-one participants, professional men (n = 8, 37 ± 6 years, 195 ± 7 cm, 113 ± 27 kg), advanced men (n = 47, 26 ± 8 years, 180 ± 7 cm, 76 ± 11 kg), and advanced women (n = 26, 21 ± 1 years, 167 ± 6 cm, 61 ± 7 kg) performed three strikes from a kneeling position into a force plate on the ground. The elbow strike resulted in the highest impulse and the palm strike in the highest peak force for all three categories. These results support the recommendation that has previously been made to teach the palm strike to beginners and advanced tactical and combat athletes. The direct punch and elbow strike net force were characterized by a double peak curve, where the first peak variability explained 70.2-84% of the net force. The second peak was pronounced in professional men during elbow strikes, which explained 16% of net force variability. The strike type determines the impact net force and its characteristics, where palm strike is typical by highest peak impact tolerance and elbow strike by double force peak with high net force impulse.

Functional performance of the upper limb and the most common boxing-related injuries in male boxers: a retrospective, observational, comparative study with non-boxing population

Background

To investigate the functional status and recording the most common injuries of the upper limb in male Greek boxing squad in comparison to the general population.

Methods

A retrospective injury surveillance study using an electronic questionnaire was performed in 2021. The questionnaire was sent to male members of the Greek Boxing Federation and consisted of three parts. Demographic data, functional status scales, training conditions, hours of training, the location and description of upper limb injuries and whether the injury occurred during competition or training and also whether it was a new or a recurrent one were gathered. The same questionnaire was sent to non-boxer males (military recruits), but without asking them to report any training parameters. Inclusion criteria were age < 35 years-old for all participants and no involvement in martial arts for the control group. Also, all participants (boxers and non-boxers) completed the Patient Rated Wrist Evaluation (PRWE) scale and the Quick Disabilities of Arm, Shoulder and Hand (quick-DASH) score.

Results

The final study cohort was consisted of 62 elite or amateur boxers and 75 non-boxer males, less than 35 years old. The quick-DASH score was found to be significantly lower (better) in boxers in comparison to the general population (15.65 ± 10.25 vs. 12.55 ± 8.62; p = 0.020) whereas the PRWE score was similar in both groups (9.25 ± 14.96 vs. 8.61 ± 13.05; p = 0.843). Physical therapy sessions, thumb injuries and boxer’s knuckle were also found to be significantly higher in the boxers group. On the other hand, upper limb surgeries were significantly less in the boxers group. Finally, the size of boxing gloves was associated to the number of finger fractures, thumb injuries and ulnar sided wrist pain in boxers.

Conclusions

Although a controversial sport, boxing appears to have no long-term consequences to the upper limb function, especially regarding hand performance. The size of gloves during heavy bag training was found to be an aggravating factor for hand injuries.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-022-00558-3.

Acute effects of ballistic versus heavy-resistance exercises on countermovement jump and rear-hand straight punch performance in amateur boxers

Background

Ballistic and heavy-resistance exercises may potentially enhance lower body power, which is paramount for the punching performance of amateur boxers. This study aimed to determine the acute effects of ballistic exercise (BE) and heavy-resistance exercise (HRE) on countermovement jump (CMJ) and rear-hand straight punch performance in amateur boxers.

Methods

Ten amateur boxers performed two conditioning exercises in a randomized and counterbalanced order as follows: squat jump with 4 sets × 8 repetitions at 30% one-repetition maximum (1RM) for BE and squat with 3 sets × 5 repetitions at 80% 1RM for HRE. The jump height (JH), relative maximal force (RMF), relative maximal power (RMP) of the CMJ, punch force (PF), and punch speed (PS) of a rear-hand straight punch were measured before and 3, 6, 9, and 12 min after either BE or HRE.

Results

No significant condition × time interaction was found for JH (p = 0.303), RMF (p = 0.875), RMP (p = 0.480), PF (p = 0.939), and PS (p = 0.939). In addition, no main effect of the condition for JH (p = 0.924), RMF (p = 0.750), RMP (p = 0.631), PF (p = 0.678), and PS (p = 0.712). A significant main effect of time was observed for PF (p = 0.001) and PS (p = 0.001), whereas JH (p = 0.081), RMF (p = 0.141), and RMP (p = 0.430) were not. Pairwise comparison identified that PF (p = 0.031) and PS (p = 0.005) significantly increased at 9 min compared with those at baseline.

Conclusions

The findings of this study demonstrated that BE and HRE protocols can potentiate the rear-hand straight punch performance at 9 min but bring less favorable improvements for JH, RMF, or RMP of CMJ.

Validity and reliability of impact forces from a commercially instrumented water-filled punching bag

Measuring striking forces is important to provide actionable insight for training and performance enhancement for combat sport athletes. Recent technology may provide a low-cost solution to an otherwise complicated kinetic assessment. The aim was to assess the reliability and validity of a water-filled training bag and integrated sensor for measuring peak impact force. A pendulum design was used to swing a range of known mass loads (kettlebells) from various heights to impact a stationary 21″ Aqua Training Bag®. For each condition, the momentum of the mass at impact was calculated and compared with the measured impact force from a pressure sensor affixed to the side of the water-filled bag. Peak impact force was strongly associated with calculated momentum (r(18) = 0.96 [0.91, 0.99], p < 0.001), with a high degree of shared variance (92.7%, F(1,18) = 229.9, p < 0.001). There was almost perfect agreement for all reliability loading conditions (ICC = 0.995–0.999) and typical error was ≤ 5% (CV = 3.3–5.1). Impact kinetics from the sensor appear to be reliable and valid and may be integrated into practice and research. However, the utility of the instrumented bag for striking kinetics of athletes, and thus practical utility when used in the field, requires further investigation.

Variability of Multiangle Isometric Force-Time Characteristics in Trained Men

ABSTRACT

Oranchuk, DJ, Storey, AG, Nelson, AR, Neville, JG, and Cronin, JB. Variability of multiangle isometric force-time characteristics in trained men. J Strength Cond Res 36(1): 284-288, 2022-Measurements of isometric force, rate of force development (RFD), and impulse are widely reported. However, little is known about the variability and reliability of these measurements at multiple angles, over repeated testing occasions in a homogenous, resistance-trained population. Thus, understanding the intersession variability of multiangle isometric force-time characteristics provides the purpose of this article. Three sessions of isometric knee extensions at 40°, 70°, and 100° of flexion were performed by 26 subjects across 51 limbs. All assessments were repeated on 3 occasions separated by 5-8 days. Variability was qualified by doubling the typical error of measurement (TEM), with thresholds of 0.2-0.6 (small), 0.6-1.2 (moderate), 1.2-2.0 (large), 2.0-4.0 (very large), and >4.0 (extremely large). In addition, variability was deemed large when the intraclass correlation coefficient (ICC) was <0.67 and coefficient of variation (CV) >10%; moderate when ICC >0.67 or CV <10% (but not both); and small when both ICC >0.67 and CV <10%. Small to moderate between-session variability (ICC = 0.68-0.95, CV = 5.2-18.7%, TEM = 0.24-0.49) was associated with isometric peak force, regardless of angle. Moderate to large variability was seen in early-stage (0-50 ms) RFD and impulse (ICC = 0.60-0.80, CV = 22.4-63.1%, TEM = 0.62-0.74). Impulse and RFD at 0-100 ms, 0-200 ms, and 100-200 ms were moderately variable (ICC = 0.71-0.89, CV = 11.8-42.1%, TEM = 0.38-0.60) at all joint angles. Isometric peak force and late-stage isometric RFD and impulse measurements were found to have low intersession variability regardless of joint angle. However, practitioners need to exercise caution when making inferences about early-stage RFD and impulse measures due to moderate-large variability.

Validation of a Novel Boxing Monitoring System to Detect and Analyse the Centre of Pressure Movement on the Boxer's Fist

The examination of force distribution and centre of pressure (CoP) displacement is a common method to analyse motion, load, and load distribution in biomechanical research. In contrast to gait analysis, the force progression in boxing punches is a new field of investigation. The centre of pressure displacement and distribution of forces on the surface of the fist during a boxing punch is of great interest and crucial to understanding the effect of the punch on the biological structures of the hand as well as the technical biomechanical aspects of the punching action. This paper presents a new method to display the CoP progression on the boxer’s fist Therefore, this study presents the validation of the developed novel boxing monitoring system in terms of CoP displacement. In addition, the CoP progression of different punching techniques in boxing is analysed on the athlete’s fist. The accuracy of the examination method of the CoP course was validated against the gold standard of a Kistler force plate. High correlations were detected between the developed sensor system and the force plate CoP with a Pearson correlation coefficient ranging from 0.93 to 0.97. The information obtained throughout the experimental study is of great importance in order to gain further knowledge into the technical execution of boxing punches as well as to provide a novel measuring method for determining CoP on the surface of the fist, to improve the understanding of the etiology of boxing-related hand injuries.

Application of a Validated Innovative Smart Wearable for Performance Analysis by Experienced and Non-Experienced Athletes in Boxing

An athlete's sporting performance depends to a large extent on the technical execution of the athletic motion in order to achieve maximum effectiveness in physical performance. Performance analysis provides an important means of classifying and quantifying athletic prowess in terms of the significant performance aspects of the sport to provide objective feedback. This study aimed to analyze technical execution in terms of punch trajectory, force, velocity and time, considering the expert-novice paradigm by investigating the technical execution of 31 experienced and non-experienced athletes for the four main punching techniques of the cross, jab, uppercut and hook strike. The kinetic and kinematic data were collected by means of a boxing monitoring system developed and validated for in-field use. The research revealed significant correlation for executed punching trajectory and punch force in intragroup comparison and significant differences in intergroup comparison. No significant differences were detected for punch velocity in either inter- or intra-group paradigms. This study, through use of the sensor system, aligns with the results of existing publications conducted in laboratory conditions, in the assessment of punch force, punch speed and punch time and thus extends the state of research by use of a smart wearable in field method.

Concurrent Validity and Reliability of Three Ultra-Portable Vertical Jump Assessment Technologies

Vertical jump is a valuable training, testing, and readiness monitoring tool used across a multitude of sport settings. However, accurate field analysis has not always been readily available or affordable. For this study, two-dimensional motion capture (Mo-Cap), G-Flight micro-sensor, and PUSH accelerometer technologies were compared to a research-grade force-plate. Twelve healthy university students (7 males, 5 females) volunteered for this study. Each participant performed squat jumps, countermovement jumps, and drop jumps on three separate occasions. Between-device differences were determined using a one-way repeated measures ANOVA. Systematic bias was determined by limits of agreement using Bland-Altman analysis. Variability was examined via the coefficient of variation, interclass correlation coefficient, and typical error of measure. Dependent variables included jump height, contact-time, and reactive strength index (RSI). Mo-Cap held the greatest statistical similarity to force-plates, only overestimating contact-time (+12 ms). G-Flight (+1.3-4 cm) and PUSH (+4.1-4.5 cm) consistently overestimate jump height, while PUSH underestimates contact-time (-24 ms). Correspondingly, RSI was the most valid metric across all technologies. All technologies held small to moderate variably; however, variability was greatest with the G-Flight. While all technologies are practically implementable, practitioners may want to consider budget, athlete characteristics, exercise demands, set-up, and processing time before purchasing the most appropriate equipment.

Biomechanical assessment of various punching techniques

Punches without the use of instruments/objects are a common type of body violence and as such a frequent subject of medicolegal analyses. The assessment of the injuries occurred as well as of the potential of the assault to produce severe body harm is based on objective traces (especially the documented injuries of both parties involved) as well as the—often divergent—descriptions of the event. Quantitative data regarding the punching characteristics that could be used for the assessment are rare and originate mostly in sports science. The aim of this study was to provide physical data enabling/facilitating the assessment of various punching techniques. A total of 50 volunteers took part in our study (29 males and 21 females) and performed severe punches with the fist, with the small finger edge of the hand (karate chop), and with the open hand with both the dominant and the non-dominant hands in randomized order. The strikes were performed on a boxing pad attached to a KISTLER force plate (sampling frequency 10,000 Hz) mounted on a vertical wall. The punching velocity was defined as the hand velocity over the last 10 cm prior to the contact to the pad and ascertained by using a high-speed camera (2000 Hz). Apart from the strike velocity, the maximum force, the impulse (the integral of the force-time curve), the impact duration, and the effective mass of the punch (the ratio between the impulse and the strike velocity) were measured/calculated. The results show a various degree of dependence of the physical parameters of the strikes on the punching technique, gender, hand used, body weight, and other factors. On the other hand, a high degree of variability was observed that is likely attributable to individual punching capabilities. In a follow-up study, we plan to compare the “ordinary” persons with highly trained (boxers etc.) individuals. Even though the results must be interpreted with great caution and a direct transfer of the quantitative parameters to real-world situations is in general terms not possible, the study offers valuable insights and a solid basis for a qualified forensic medical/biomechanical assessment.

Variability of Regional Quadriceps Architecture in Trained Men Assessed by B-Mode and Extended-Field-of-View Ultrasonography

PURPOSE

Regional muscle-architecture measures are reported widely; however, little is known about the variability of these measurements in the rectus femoris, vastus lateralis, and anterior and lateral vastus intermedius. The aim of this study was to quantify this variability.

METHODS

Regional muscle thickness, pennation angle (PA), and calculated and extended-field-of-view-derived fascicle length (FL) were quantified in 26 participants using ultrasonography across 51 limbs on 3 occasions. To quantify variability, the typical error of measurement (TEM) was multiplied by 2, and thresholds of 0.2-0.6 (small), 0.6-1.2 (moderate), 1.2-2.0 (large), 2.0-4.0 (very large), and >4.0 (extremely large) were applied. In addition, variability was deemed large when the intraclass correlation coefficient (ICC) was <.67 and coefficient of variation (CV) >10%, moderate when ICC > .67 or CV < 10% (but not both), and small when both ICC > .67 and CV < 10%.

RESULTS

Muscle thickness of all muscles and regions had low to moderate variability (ICC = .88-.98, CV = 2.4-9.3%, TEM = 0.15-0.47). PA of the proximal and distal vastus lateralis had low variability (ICC = .85-.96, CV = 3.8-8%) and moderate to large TEM (TEM = 0.42-0.83). PA of the rectus femoris was found to have moderate to very large variability (ICC = .38-.74, CV = 11.4-18.5%, TEM = 0.61-1.29) regardless of region. Extended-field-of-view-derived FL (ICC = .57-.94, CV = 4.1-11.5%, TEM = 0.26-0.88) was superior to calculated FL (ICC = .37-.84, CV = 7.4-17.9%, TEM = 0.44-1.33).

CONCLUSIONS

Variability of muscle thickness was low in all quadriceps muscles and regions. Only rectus femoris PA and FL measurements were highly variable. The extended-field-of-view technique should be used to assess FL where possible. Inferences based on rectus femoris architecture should be interpreted with caution.

Variability of regional quadriceps echo intensity in active young men with and without subcutaneous fat correction

Quantifying echo intensity (EI), a proposed measure of muscle quality, is becoming increasingly popular. Additionally, much attention has been paid to regional differences in other ultrasonically evaluated measures of muscle morphology and architecture. However, the variability of regional (proximal, middle, distal) EI of the vastus lateralis, rectus femoris, and lateral and anterior vastus intermedius has yet to be determined. Twenty participants (40 limbs), were evaluated on 3 occasions, separated by 7 days. Intersession variability of EI with and without subcutaneous fat correction was quantified. Furthermore, the interchangeability of corrected EI across regions was evaluated. Variability of regional quadriceps EI was substantially lower with subcutaneous fat correction (intraclass correlation coefficient (ICC) = 0.81-0.98, coefficient of variation (CV) = 4.5%-16.8%, typical error of measure (TEM) = 0.13-0.49) versus raw values (ICC = 0.69-0.98, CV = 7.7%-42.7%, TEM = 0.14-0.68), especially when examining the vastus intermedius (ICC = 0.81-0.95, CV = 7.1%-16.8%, TEM = 0.23-0.49 vs. ICC = 0.69-0.92, CV = 22.9%-42.7%, TEM = 0.31-0.68). With the exception of the rectus femoris and vastus intermedius (p ≥ 0.143, effect size (ES) ≤ 0.18), corrected EI was greater for proximal and distal regions when compared with the midpoint (p ≤ 0.038, ES = 0.38-0.82). Researchers and practitioners should utilize subcutaneous fat thickness correction to confidently evaluate EI at all regions of the quadriceps. Regional EI cannot be used interchangeably for the vastus muscles, likely because of an increase in fibrous content towards the myotendinous junctions. Novelty Regional quadriceps echo intensity was reliable with and without correction for subcutaneous fat thickness. Intersession variability of regional quadriceps echo intensity was substantially improved following subcutaneous fat correction. Quadriceps echo intensity increased towards myotendinous junctions in the vastus muscles.