Klaus Wirth

Goethe University Frankfurt · Institute of Sports Sciences

This article has been accepted for publication in "Journal of Strength and Conditioning Research"

Introduction While maximum strength diagnostics are applied in several sports and rehabilitative settings, dynamic strength capacity has been determined via the one-repetition maximum (1RM) testing for decades. Because the literature concerned several limitations, such as injury risk and limited practical applicability in large populations (e.g., a...

This study critically examines the suitability of using a single drop height to assess the reactive strength index (RSI) in trained and active participants, a key component of athletic performance. Using a cross-sectional design, 377 trained (n = 163) and active (n = 214) participants aged 14 to 18 years performing drop jumps (DJs) from four differ...

When measuring maximum strength, a high accuracy and precision is required to monitor the training adaptations. Based on available reliability parameters, the literature suggests the replacement of the one repetition maximum (1RM) by isometric testing to save testing time. However, from a statistical point of view, correlation coefficients do not p...

The mechanisms underlying range of motion enhancements via flexibility training discussed in the literature show high heterogeneity in research methodology and study findings. In addition, scientific conclusions are mostly based on functional observations while studies considering the underlying physiology are less common. However, understanding th...

Objectives Maximal strength is considered a fundamental aspect of athletic performance across a wide range of sports and is also needed for a range of activities of daily life. Yet, compared to males there are fewer publications examining females, with most showing similar coefficients of correlation between dynamic strength and different athletic...

Background Increases in maximal strength and muscle volume represent central aims of training interventions. Recent research suggested that the chronic application of stretch may be effective in inducing hypertrophy. The present systematic review therefore aimed to syntheisize the evidence on changes of strength and muscle volume following chronic...

Soccer is a complex sports discipline that requires players to engage in diverse high-intensity and multidirectional activities. The optimization of strength and conditioning programs requires a comprehensive understanding of the physical attributes influencing player performance. While previous research has demonstrated the influence of knee and h...

The purpose of this study was to investigate the concordance of isokinetic bilateral strength differences of the knee extensors in single- and multi-joint movement tasks. One hundred and nineteen male athletes performed isokinetic legpresses at 0.1 m/s and 0.7 m/s as well as isokinetic knee extensions at 60°/s and 180°/s. Bilateral differences and...

Introduction: Based on the assumption of maximal strength as a basic ability,several studies show a high influence of maximum strength on jumping performance in several sport athletes. However, there is a wide range ofcorrelations from r = 0.17–0.9 between squat 1RM and jumping performancein different sports. Additionally, there are only a few stud...

Objectives: In ice hockey, speed strength is one of the major physical key performance indicators, which is significantly influenced by maximum strength. The objective of this study was to evaluate the age dependent relationship between off-ice maximum strength and vertical jump performance, with on-ice linear sprint performance considering age an...

Background Accurate measurements of muscular performance are important for diagnostics, for example during rehabilitation after traumatic injuries but also in competitive sports. For these purposes, dynamometric devices are widely used and considered the gold standard for muscle strength testing. However, few previous studies have tested the reprod...

Increasing muscle strength and cross-sectional area is of crucial importance to improve or maintain physical function in musculoskeletal rehabilitation and sports performance. Decreases in muscular performance are experienced in phases of reduced physical activity or immobilization. These decrements highlight the need for alternative, easily access...

Swimmers reach the highest accelerations during starts. These are initiated by a high amount of force produced by the lower limbs in a short amount of time. It is established in senior athletes that there is a relationship between lower-body maximum strength and swim start performance. The aim of this study was to investigate the relationship betwe...

Vertical jumping performance is of high importance for various individual and team sports. Movement patterns utilizing a stretch shortening cycle are of particular interest. Despite their involvement in every vertical jump variation, the importance of the plantar flexors’ dynamic maximum strength for jumping performance has not been investigated ye...

Maximal strength measured via maximal voluntary contraction is known as a key factor in competitive sports performanceas well as injury risk reduction and rehabilitation. Maximal strength and hypertrophy are commonly trained by performingresistance training programs. However, literature shows that long-term, long-lasting static stretching intervent...

Speed strength performances are heavily dependent on maximum strength. However, various strength testing methods determined inconsistent relationships between absolute and relative strength and sprint and jump performances. The aim of the study was to calculate the one tailed correlation coefficients between both the One-Repetition Maximum (1RM)...

Introduction: Speed-strength performance is important during human movements such as jumping, sprinting, and change of direction (COD) tasks, which are a substantial part of sports practice. Sex and age seem to influence performance output in young persons; however, few studies have focused on the influence of sex and age measured via standard prot...

Contact injuries are difficult to prevent in sports because of the influence of many uncontrollable factors. Non-contact injuries, on the other hand, appear to be controllable and therefore predictable due to their exclusively internal nature. Nevertheless, the scientific community is still searching in vain for indicators to reliably predict the l...

Measuring maximal strength (MSt) is a very common performance diagnoses, especially in elite and competitive sports. The most popular procedure in test batteries is to test the one repetition maximum (1RM). Since testing maximum dynamic strength is very time consuming, it often suggested to use isometric testing conditions instead. This suggestion...

Animal studies show that long-lasting stretching training can lead to significant hypertrophy and increases in maximal strength. Accordingly, previous human studies found significant improvements in maximal voluntary contraction (MVC), flexibility and muscle thickness (MTh) using constant angle long-lasting stretching. It was hypothesized that long...

To improve flexibility, stretching is most commonly used and in training interventions duration-dependent effects are hypothesized. However, there are strong limitations in used stretching protocols in most studies, particularly regarding documentation of intensity and performed procedure. Thus, aim of this study was to compare different stretching...

Introduction An increasing number of studies investigate the influence of training interventions on muscle thickness (MT) by using ultrasonography. Ultrasonography is stated as a reliable and valid tool to examine muscle morphology. Researches investigating the effects of a training intervention lasting a few weeks need a very precise measurement s...

Speed strength performances are substantially dependent on maximum strength. Due to its importance, various methods have been utilized to measure maximum strength (e.g., isometric or dynamic) with discussed differences regarding transferability to sport specific movements dependent on testing procedure. The aim of this study was to analyze whether...

Background. Strength and speed are two major factors that determine performance in basketball players especially sprinting, jumping and change of direction. This study examined relationships of maximal strength in the front squat and the deadlift with basketball specific sprint and jump performance tests that are commonly used in test batteries of...

Many sports injuries result in surgery and prolonged periods of immobilization, which may lead to significant atrophy accompanied by loss of maximal strength and range of motion and, therefore, a weak-leg/strong-leg ratio (as an imbalance index ) lower than 1. Consequently, there are common rehabilitation programs that aim to enhance maximal stren...

The so called “stretch-induced force deficit” is known from a large number of research. There are many theories trying to explain the stretch-induced force deficit and increases in the range of motion (ROM) which all offer a stretch training specific explanation. However, when performing a commonly used strength training session a reduced maximum s...

Unterschiede in den Korrelationsstärken zwischen isometrischen und dynamischen Kraftmessungen sowie Sprungleistungen bei Nachwuchsfußballern

Einleitung Der Anstieg der Maximalkraft ist Ziel einer Vielzahl von Trainingsprogrammen in Prävention und Rehabilitation. Um Maximalkraft- und Muskeldickenzuwächse zu erzeugen, wird im Regelfall ein Krafttraining durchgeführt. Ergebnisse aus Tierstudien zeigen jedoch, dass auch langanhaltende Dehnungsspannungen zu signifikanten Muskelmasse- und Ma...

The current study aimed to compare the effects of plyometric and sprint vs. functional vs. strength training on linear sprint (LS 20 m), change of direction (COD; i.e., turning right and left), jump (squat jump [SJ]), and maximum strength (1 repetition maximum [1RM] for a quat) performance in elite adolescent soccer players. A longitudinal design w...

Problem: Since segment lengths of the lower extremities influence joint kinematics in multi-joint movements, anthropometric standardization seems necessary to study the force-length-velocity relationships of muscles in vivo. Mathematical approaches to calculate the needed linear velocities for the desired angular kinematics from individual anthropo...

Previous research points out high relevance of maximal strength measurement in the diagnostics of different populations. However, there is inconsistency in procedures of maximum strength measurements. Thus, it must be questioned whether the results from different studies are actually comparable. Due to the aforementioned problems in standardization...

In basketball high intensity jumping and sprinting performance is of high importance. There seems to be a relationship between maximal strength (MSt) and jumping performance in general, but influence of MSt in the plantar flexors and jumping performance seems not to be investigated very well. Thus, the aim of this study was to investigate the influ...

PurposeMuscle strength and power are important requirements in many sports. The correlation of jumping performance as manifestation of muscle power and squatting one-repetition maximum (1RM) has been shown in several investigations. Correlations with maximum force in a linear isokinetic leg press are still pending. Since different testing devices p...

This study aims to analyze the influence of relative strength performance, determined by parallel back squats (REL SQ), on 30 m sprinting (LS) and on jumping performance (squat [SJ], countermovement [CMJ]) in a large sample (n = 492) of elite youth soccer players. The soccer players were divided into subgroups based on their strength performance: s...

This narrative review deals with the topic of strength training in swimming, which has been a controversial issue for decades. It is not only about the importance for the performance at start, turn and swim speed, but also about the question of how to design a strength training program. Different approaches are discussed in the literature, with two...

A high level of sprinting performance is relevant in various sports. Because of the transition of movement patterns in different sprint sections there is a shift in the relevance of speed-strength of the knee and hip extensors, and stretch-shortening cycle performance seems conceivable. Fifty-six physical education students (23.70 ± 3.00 years, 176...

The aim of this investigation was to analyze significant differences in performance depending on the level of play (elite vs. amateur) in youth soccer players (under 17 years. old (U17) and U19). A cross-sectional study was conducted, and 45 elite and amateur male youth soccer players (16.56 +/- 0.9 years old) were evaluated in their performances i...

Keiner, M, Wirth, K, Fuhrmann, S, Kunz, M, Hartmann, H, and Haff, GG. The influence of upper-and lower-body maximum strength on swim block start, turn, and overall swim performance in sprint swimming. J Strength Cond Res XX(X): 000-000, 2019-Maximum strength and speed strength are 2 major factors that determine a swimmer's performance, including sw...

Artistic gymnastics consist of a high amount of jumping actions with rotations around one or more axes. To achieve an optimal flight height to perform the desired number of rotations, the movement pattern and the floor characteristics have to be concerted optimally. To account for the required leg stiffness to utilize the floor’s elasticity, the le...

Background: Speed and strength performance have an essential role in soccer. It is well known there is a moderate to strong correlation between maximum strength, speed and jump performance. However most studies have analyzed only maximum strength values of the knee and hip extensors for the correlation analysis. Studies on the maximum strength of t...

Die Durchführung eines Krafttrainings im Schwimmsport stellt ein seit Jahr-zehnten kontrovers diskutiertes Thema dar. Dabei geht es sowohl um die Be-deutung für die Leistung bei Start, Wenden und die Schwimmgeschwindigkeit, als auch um die Frage, wie ein Krafttraining zu gestalten ist. Unabhängig von der Leistungsentwicklung der Sportler, sollten a...

Möck, S, Hartmann, R, Wirth, K, Rosenkranz, G, and Mickel, C. Relationship between maximal dynamic force in the deep back squat and sprinting performance in consecutive segments up to 30 m. J Strength Cond Res XX(X): 000-000, 2018-The sprint (in track and field athletics) is characterized by a fluent transition from predominantly knee extending mus...

Change of direction (COD) performance has an essential role in soccer. In the literature, there is a wide range of explained variance in correlation analyses between linearsprint performance, concentric power and maximum strength and COD performance. Therefore this study has (1) analyzed the influence of linear-sprint performance, concentric power...

Water polo is a multifaceted sport that is characterized by explosive actions, including sprint swimming, jumping, throwing, and struggling against opponents. Based upon these factors, maximal and speed strength may be important characteristics to develop in water polo players. However, more research is needed to further understand the relationship...

Problem: Sprinting represents a relevant task in many sports. The correlation of sprinting performance and squatting strength (1RM) has been shown in several investigations. Correlations with maximum strength in a linear isokinetic leg press are still pending. Since different devices produce different relationships and rotational isokinetic measure...

Change of direction (COD) is a performance limiting factor in team sports. However, there are no exact definitions of which physical abilities limit the COD performance. Nevertheless, different methods are used or are recommended as equally effective in professional practices to measure COD performance. Therefore, the aim of this study is to evalua...

Purpose: To evaluate the predictive validity of critical power (CP) and the work above CP (W') on cycling performance (mean power during a 20-min time trial; TT20). Methods: On 3 separate days, 10 male cyclists completed a TT20 and 3 CP and W' prediction trials of 1, 4, and 10 min and 2, 7, and 12 min in field conditions. CP and W' were modeled...

Sprinting is characterized by a transition from propulsion via knee extending musculature during initial acceleration towards ischiocrural musculature thereafter. This may lead to a decrease of correlation of the maximal strength in the back squat and sprinting performance with increasing distance. The aim of this investigation was to show the corr...

This study was designed to evaluate the effects of long-term (2 years) strength training on reactive strength. To control the effect of the strength training intervention, reference data in trained and untrained adolescents were determined. Therefore, part 1 of this investigation evaluated a cross-sectional analysis of untrained adolescents (studen...

Sprinting represents a result-relevant task in many sports. The correlation of sprinting performance and one-repetition maximum (1RM) in a squat has been assumed as assured. Results of the correlation with 1RM of the plantar flexors are still pending. Assuming an increasing relevance of the reactive working capacity with increasing distance, a decr...

To assess the validity and reliability of the Garmin Vector against the SRM power meter, 6 cyclists completed 3 continuous trials at power outputs from 100-300 W at 50-90 rev·min(-1) and a 5-min time trial in laboratory and field conditions. In field conditions only, a 30-s sprint was performed. Data were compared with paired samples t-tests, with...

Over the last two decades, exercise of the core muscles has gained major interest in professional sports. Research has focused on injury prevention and increasing athletic performance. We analyzed the guidelines for so-called functional strength training for back pain prevention and found that programs were similar to those for back pain rehabilita...

The aim of this study was to evaluate the effectiveness of free-weight and machine-based exercises to increase different strength and speed-strength variables. One hundred twenty male participants (age: 23.8 ± 2.5 years; body height: 181.0 ± 6.8 cm; body mass: 80.2 ± 8.9 kg) joined the study. The 2 experimental groups completed an 8 week periodiz...

Despite the common use of jogging strollers, only a few studies cover their influence on running patterns. Kinematic studies have shown differences in the upper body movement, while potential changes in plantar pressure remain unclear. Therefore, 30 healthy sport students were asked to run at a self-selected speed with and without a jogging strolle...

For the development of speed strength in professional sports, “specific” strength training in the half or the quarter squat have been recommended. Due to the better lever ratios, higher loads have to be used to induce the necessary training stimuli compared to the deep squat. Therefore, intradiscal pressure and compressive forces on vertebral bodie...

Strength training-induced increases in speed-strength seem indisputable. For trainers and athletes the most efficient exercise selection in the phase of preparation is of interest. Therefore, this study determined how the selection of training exercise influences the development of speed-strength and maximal strength during an 8-week training inter...

This study investigated the trainability of decision-making and reactive agility via video-based visual training in young athletes. Thirty-four members of a national football academy (age: 14.4 � 0.1 years) were randomly assigned to a training (VIS; n = 18) or a control group (CON; n = 16). In addition to the football training, the VIS completed a...

The purpose of this study was to establish whether physical attributes can differentiate between professional, amateur and elite youth soccer players; such a distinction could aid in the selection process for youth soccer. Therefore, this investigation evaluated a suspected difference in the performance tests of the slow and fast stretch and the sh...

The training of the trunk muscles has become a standard practice for improving strength and speed-strength and reducing one’s susceptibility to injury. Athletic movements, such as sprints, lead to high forces acting on the torso and hips. The trunk muscles must control the extremities and transfer these forces so that efficient locomotion is ensure...

Dividing training objectives into consecutive phases to gain morphological adaptations (hypertrophy phase) and neural adaptations (strength and power phases) is called strength-power periodization (SPP). These phases differ in program variables (volume, intensity, and exercise choice or type) and use stepwise intensity progression and concomitant d...

The aim of this investigation was to analyze the effects of an eccentric strength training protocol using supramaximal loads (> 1RM; 1RM = one-repetition maximum) on different maximal and explosive strength parameters of the lower extremity. The eccentric maximal strength (EX max), maximal isometric strength (MVC = "maximal voluntary contraction"),...

Abstract Objectives. - Strength and speed are 2 major factors that determine a swimmer’s sprint performance, especially swim sprint performance and swim starts. This study identified and examined variables that determine the influence of maximal strength performance on different swim performance styles and distances in trained adolescent swimmers....

For track, field and team sports, many authors advise sport-specific strength training with half and quarter squats instead of parallel squats. Due to the sport-specific argument, higher correlations with sprint performance could be expected for half and quarter squats. Hence, correlations between sprint performance (30 m linear sprint) and both On...

Objectives An early-established strength training regimen brings many benefit young athletes, especially those engaged in competitive sports. Strength training also leads to improve athletic performance, strength training is used for rehabilitation and injury prevention. The aim of this study was to evaluate how 2 years of additional strength trai...

The aim of the study was the evaluation of the correlation between maximal strength and muscle mass depending on the kind of analysis which was used. Two different methods of strength evaluation and several morphological parameters were used. 77 male participants (age: 27,2 ± 6,6 years; body height: 179,9 ± 4,0 cm; body weight: 82,5 ± 10,4 kg) join...

Erweiterter Überblicksartikel mit detaillierter Diskussion über die korrekte Übungsausführung der tiefen Kniebeuge 1. Mechanische Belastung und Beanspruchung des tibio- und patellofemoralen Gelenks in Abhängigkeit von Kniebeugetiefe und Lasthöhe 2. Kniegelenk- und Wirbelsäulenbelastung in der Kniebeuge in Abhängigkeit von der Übungsausführung 3....