Recovery Kinetics After Different Sprint Training Protocols (STRecovery)
Condition: Sprint Training
Study type: Interventional

Summary: 
      Speed is one of the most important physical capacities for many sports, especially those that
      include speed and power as a major element, and plays a major role on performance. Running
      speed improvement is one of the most basic components of a sprint and power athlete's
      training program. One of the most commonly used strategies to improve the initial
      acceleration phase, is resisted sprint training. Sprinting is performed through the
      stretch-shortening cycle and highly includes the component of eccentric muscle contraction,
      which can lead to exercise induced muscle damage (EIMD). This phenomenon includes symptoms
      such as plasma CK elevation, delayed onset of muscle soreness, reduction in force production
      and a reduction in agility and speed. However, despite the fact that sprint training can
      cause EIMD symptoms and a performance reduction the following days, research evidence on the
      recovery kinetics after sprint training are scarce. However, such information is critical for
      coaches and athletes, in order to effectively design a training program and incorporate the
      training components in the training microcycle, to avoid injuries and maximize performance.
      The aim of the present study is to examine the recovery kinetics of EIMD indices, muscle
      performance and neuromuscular fatigue, after different sprint training protocols.
    

Detailed description: 
      Speed is one of the most important physical capacities for many sports, especially those that
      include speed and power as a major element, and plays a major role on performance. Thus,
      running speed improvement consists one of the most basic aims of a sprinter's and a power
      athlete's training program. One of the most commonly used strategies to improve the initial
      acceleration phase, is resisted sprint training. Evidence suggests that resisted sprint
      training is more effective in improving acceleration compared to sprint training without
      additional load. Sprinting is performed through the stretch-shortening cycle, where the
      pre-activated muscle is first stretched (eccentric action) and then followed by the
      shortening (concentric) action. Thus, sprint training highly includes the component of
      eccentric contraction. However, eccentric muscle action, especially when unaccustomed, can
      lead to exercise-induced muscle damage (EIMD). Although concentric and isometric exercise may
      also lead to muscle injury, the amount of damage after eccentric muscle contractions is
      greater. EIMD, amongst others, is accompanied by increased levels of creatine kinase (CK)
      into the circulation, increased delayed onset of muscle soreness (DOMS), reduction of force
      production, reduction of agility and speed. Nevertheless, despite the fact that sprint
      training comprises eccentric muscle actions and consequently can lead to muscle injury and
      muscle performance reduction during the following days, the recovery kinetics after acute
      sprint training have not been adequately studied. However, such information is critical for
      both coaches and athletes to effectively design the training microcycles and incorporate the
      training components, as well as to reduce injury risk.

      The aim of the present study is to examine the recovery kinetics of EIMD indices, muscle
      performance and neuromuscular fatigue, after different sprint training protocols.

      According to a preliminary power analysis (a probability error of 0.05, and a statistical
      power of 80%), a sample size of 8 - 10 subjects per group was considered appropriate in order
      to detect statistically meaningful changes between groups.

      The study will be performed in a randomized, cross over, repeated measures design. During the
      first 1st and 2nd visit, all participants will sign an informed consent form after they will
      be informed about all the benefits and risks of the study and they will fill in and sign a
      medical history questionnaire. Fasting blood samples will be collected in order to estimate
      muscle damage concentration markers. Participants will be instructed by a dietitian how to
      record a 7-days diet recalls to ensure that they do not consume to greater extent nutrients
      that may affect EIMD and fatigue (e.g. antioxidants, amino acids, etc.) and to ensure that
      the energy intake during the trials will be the same. Assessment of body mass and body
      height, body composition, and aerobic capacity (VO2max), will be performed. Running speed of
      10 m, 20 m and 30 m sprint will be measured on a track and field stadium. Squat jump and
      countermovement jump will be performed on a force platform to assess jump height, ground
      reaction force, peak and mean power, vertical stiffness and peak rate of force development;
      at the same time, peak and mean normalized EMG during the concentric phase of the squat jump,
      and during eccentric and concentric phases of the counter movement jump, for the vastus
      lateralis, biceps femoris, gastrocnemius, and gluteus maximum muscles will be assessed. The
      peak concentric, eccentric and isometric isokinetic torque of the knee flexors and extensors,
      in both limbs will be evaluated on an isokinetic dynamometer at 60°/sec. Maximal voluntary
      isometric contraction (MVIC) of the knee extensors at 65o in both limbs, as well as the
      fatigue rate during MVIC through the percent drop of peak torque between the first and the
      last three seconds of a 10-sec MVIC.

      During the 3rd visit, participants will be randomly assigned into, and perform one of the
      four different conditions of the study design: a) unresisted sprint training, b) resisted
      sprint training with a load of 10% of body weight (BW), c) resisted sprint training with a
      load of 20% of BW d) control condition. Prior to each experimental protocol, assessment of
      DOMS in the knee flexors (KF) and extensors (KE) of both limbs, as well as blood lactate
      assessment will be performed. Additionally, DOMS of KF and KE, running speed at 10 m, 20 m
      and 30 m sprint, peak concentric, eccentric and isometric isokinetic torque, squat and
      countermovement jump height, as well as ground reaction force, peak and mean power, vertical
      stiffness and peak rate of force development during squat and countermovement jump, alongside
      with peak and mean normalized electromyography (EMG) during the concentric phase of the squat
      jump, and during eccentric and concentric phases of the counter movement jump, for the vastus
      lateralis, biceps femoris, gastrocnemius, and tibialis anterior muscles will be assessed
      immediately after, 24h, 48h and 72h after the end of the trial. MVIC of the knee extensors of
      both limbs, as well as the fatigue rate during MVIC will also be assessed at 1h, 2h and 3h,
      as well as 24h, 48h, and 72h after the end of the trial. Blood lactate will also be assessed
      at 4 min, while creatine kinase at 24h, 48h, and 72h after the end of the trial. The exact
      above procedures will be repeated by the participants during the remaining three experimental
      trials (7th - 10th, 11th - 13th, and 14th - 16th visits).
    

Intervention name(s): Unresisted sprint training; Resisted sprint training with load equal to 10% of body weight; Resisted sprint training with load equal to 20% of body weight; Control trial
Intervention type(s): Other; Other; Other; Other
Intervention description(s): Particiapants will perform:
2 sets of 3 x 20m sprint
1 set of 3 x 30m sprint; Particiapants will perform:
2 sets of 3 x 20m sprint
1 set of 3 x 30m sprint; Particiapants will perform:
2 sets of 3 x 20m sprint
1 set of 3 x 30m sprint; Participants will not perform any sprint training protocol
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Screening
Keywords: sprint training; muscle damage; muscle performance; neuromuscular fatigue; recovery