The relationship between leg stiffness, forces and neural control of the leg musculature during the stretch-shortening cycle is dependent on the anticipation of drop height
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This study aimed at investigating how prior knowledge of drop heights affects proactive and reactive motor control in drop jumps (DJ).
In 22 subjects, the effect of knowledge of three different drop heights (20, 30, 40 cm) during DJs was evaluated in seven conditions: three different drop heights were either known, unknown or cheated (announced 40 cm, but actual drop height was 20 cm). Peak ground reaction force (Fmax) to body weight (BW) ratio (Fmax/BW) and electromyographic (EMG) activities of three shank and five thigh muscles were assessed 150 ms before and during ground contact (GC). Ankle, knee and hip joint kinematics were recorded in the sagittal plane.
Leg stiffness, proactive and reactive EMG activity of the leg muscles diminished in unknown and cheat conditions for all drop heights (7–33% and 2–26%, respectively). Antagonistic co-activation increased in unknown (3–37%). At touchdown, increased flexion in knee (~ 5.3° ± 1.9°) and hip extension (~ 2° ± 0.6°) were observed in unknown, followed by an increased angular excursion in hip (~ 2.3° ± 0.2°) and knee joints (~ 5.6° ± 0.2°) during GC (p < 0.05). Correlations between changes in activation intensities, joint kinematics, leg stiffness and Fmax/BW (p < 0.05) indicate that anticipation changes the neuromechanical coupling of DJs. No dropouts were recorded.
These findings underline that anticipation influences timing and adjustment of motor responses. It is argued that proactive and reactive modulations associated with diminished activation intensities in leg extensors are functionally relevant in explaining changes in leg stiffness and subsequent decline in performance.
KeywordsNeuromuscular Jump Electromyography Reactive Fmax Prediction Unpredicted
M. biceps femoris
Central nervous system
Center of mass
Peak ground reaction force
Ground contact time
M. gastrocnemius lateralis
M. gluteus maximus
Integrated electromyographic activity
Muscle tendon unit
Maximal voluntary contraction
M. rectus femoris
Repeated-measures analysis of variance
M. tibialis anterior
M. vastus lateralis
M. vastus medialis
This study was funded by the German Aerospace Center (DLR, FKZ 50WB1715).
MH designed and conducted the experiment, collected and analysed the data and wrote the manuscript. KF designed the experiment, analysed data and edited manuscript. JW collected data, designed and conducted the experiment and analysed data. AB designed the experiment and edited manuscript. RR designed the experiment, analysed data and edited manuscript. All authors read and approved the manuscript.
Compliance with ethical standards
Conflict of interest
The authors have no conflicts of interest related to this study.
- Benjamini Y, Hochberg Y (1995) Controlling the false discovery rate: a practical and powerful approach to multiple testing. J R Stat Soc Ser B (Methodological) 57:289–300Google Scholar
- Cohen J (1988) Statistical power analysis for the behavioral sciences, 2nd edn. Erlbaum, HillsdaleGoogle Scholar
- Fong SSM, Ng SSM, Guo X, Wang Y, Chung RCK, Stat G, Ki WY, Macfarlane DJ (2015) Deficits in lower limb muscle reflex contraction latency and peak force are associated with impairments in postural control and gross motor skills of children with developmental coordination disorder: a cross-sectional study. Medicine 94:e1785CrossRefPubMedPubMedCentralGoogle Scholar
- Jidovtseff B, Quievre J, Harris NK, Cronin JB (2014) Influence of jumping strategy on kinetic and kinematic variables. J Sports Med Phys Fit 54:129–138Google Scholar
- Konrad P (2006) The ABC of EMG: a practical introduction to kinesiological electromyography. Noraxon USA, Inc, ScottsdaleGoogle Scholar
- Leonhart R, Schornstein K, Groß J (2004) Lehrbuch Statistik. Einstieg und Vertiefung. Huber, BernGoogle Scholar
- Marsden CD, Merton PA, Morton HB, Adam JER, Hallett M (1978) Automatic and voluntary responses to muscle stretch in man. Prog Clin Neurophysiol 4:167Google Scholar
- Mayer F, Baur H, Deibert P, Schmitt S, Gollhofer A (2007) Prävention von Verletzungen bei Stolper-, Rutsch- und Sturzunfällen. Einflussfaktoren von Fersenbeinfrakturen. Entwicklung einer Prüfapparatur und Evaluation präventiver Maßnahmen zur Verhütung von FersenbeinfrakturenGoogle Scholar