Acute Study: Changes in Sprint Kinematics and Kinetics with Upper Body Loading and Lower Body Loading Using EXOGEN® Exoskeletons

Simperingham and Cronin (9)

 

Purpose Statement:

To compare the effects of different WR placements on maximal sprinting performance using a non-motorised treadmill.

 

Introduction:

WR of 5% BM was attached to either the upper and lower body (Figure 11). Eight sport science students performed four sets of two 6 second sprints on a non-motorised treadmill.

Figure 11: Lower and upper body WR

Key Findings:

  1. For the same relative load (5% BM), greater changes with lower body WR were found compared to upper:
    1. the time to cover distances above 10 m and the peak velocities achieved during AP and MVP were significantly slower by -2.3 to -4.2 % with lower WR
    2. lower WR resulted in a – 2.9 % reduction in step frequency during acceleration
  2. Lower body WR loading resulted in increased vertical GRF (up to 5%), while altering peak velocity, contact time and step frequency (< 5 %).
  3. Upper body WR did not alter velocity but reduced FT up to 15% and consequently decreased vertical GRF relative to BM (up to 6 %).
  4. 7 out of 8 participants perceived improved unloaded sprint performance following four sprints with WR.

Practical Applications:

  1. Lower body loading rather than upper body loading at 5% BM appears to provide a more effective vertical stimulus to increase eccentric strength and muscle stiffness.
  2. For athletes wanting to overload the start and acceleration phase of a sprint, lower body loading may be used to increase GRF and step variables.
  3. A series of sprints with WR may be an effective pre-conditioning stimulus to induce a perception of potentiated unloaded sprint acceleration performance.

 

Link to Publication

 

 

Acute Study: Acute Changes in Sprint Running Performance Following Ballistic Exercise with Added Lower Body Loading

Simperingham, Cronin (10)

 

Purpose Statement:

To compare the effects of different WR magnitudes during loaded warm-ups on over ground sprint performance.

 

Introduction:

WR of 1, 3 and 5% BM was attached to the lower body to assess the effects of different loaded warm-ups on sprinting (Figure 12). One male athlete performed three unloaded 40 m over the ground sprints following different ballistic warm-up methods with WR. Each condition was performed on a separate day.

Figure 12: Thigh and shank WR

Key Findings:

  1. The loaded accelerations and loaded warm-up resulted in longer contact time (3-4%) during initial acceleration, enabling more time for horizontal force application, lower step frequency (-1 to -3%) during acceleration and a substantial acute improvement in sprint performance.
  2. Overloading the vertical force pattern with drop jumps and the more upright flying sprints did not result in a change in sprint acceleration performance.

 

Practical Applications:

Lower body WR 3% BM worn during a dynamic speed warm-up 40 m accelerations appears to be effective at acutely improving subsequent unloaded sprint at 10, 30 and 40 m performance, perhaps by providing a non-verbal cue for improved lower limb sprint mechanics.

 

Link to Publication

 

Acute Study: Changes in Acceleration Phase Sprint Biomechanics with Lower Body Wearable Resistance

Simperingham, Cronin (11)

 

Purpose Statement:

How do different WR loads of the whole leg effect 20 m sprint performance.

 

Introduction:

Fifteen male amateur rugby players performed three 20 m over the ground sprints with either WR of 3% or 5% BM whole leg loading.

 

Key Findings:

  1. No significant changes in sprint times over 10 m with either load but the 20 m sprint time with 5% loading was significantly slower than unloaded (-2%) and 3% condition (-1%).
  2. Significant decrease in theoretical maximum velocity (V0) (-5 to -6%) with both loads and non-significant increase in theoretical horizontal force production (F0) (4%) but only with 3% BM.
  3. Theoretical maximum horizontal power output (Pmax) increased with 3% BM (1.2%, p > 0.05) compared to unloaded, though 5%BM WR was significantly decreased (-4.2%) compared to the 3%BM condition.
  4. Significant changes to contact time (4.3-4.5%) and step frequency (-1.7-2.6%). No significant changes to step length or flight time.

 

Practical Applications:

  1. 3% BM WR serves to increase horizontal force output during the acceleration phase of sprinting and may be suitable for athletes seeking to improve horizontal force and power during sprint acceleration.
  2. Athletes can be safely loaded up to 5% BM without substantially altering sprint mechanics.
  3. No change in sprint time at 10m with either load, therefore, >5%BM may be needed to overload the early acceleration phase.

 

Link to Publication

 

Acute Study: Acute Kinematic and Kinetic Adaptations to Wearable Resistance During Sprint Acceleration

Macadam, Simperingham (12)

 

Purpose Statement:

How do different WR placement of the whole leg effect 20 m sprint performance.

 

Introduction:

Nineteen amateur to semi-professional rugby males performed two 20 m over the ground sprints unloaded and with each WR condition: 3% BM either attached to the anterior or posterior surface of the lower body (Figure 13).

Figure 13: WR of 3% BM: Anterior and Posterior Positions

Key Findings:

  1. No significant decrease in time over 20 m, but significant decrease in theoretical maximum velocity (V0) (-5.4 to -6.5 %)
  2. Significant decrease in F-v slope (-10 to -11 %) was found, while a non-significant increase in theoretical maximum horizontal force (F0) (4.9-5.2 %) occurred.
  3. Significant increase in contact time (3.0-4.4%), and decrease in vertical stiffness (-6.2% to -12.0%), SF (3.4% to -3.6%). No change in step length or flight time.
  4. No significant difference between anterior or posterior load positions.

 

Practical Applications:

  1. No difference between anterior or posterior load positions in mechanical loading measures.
  2. 3% BM WR allows individuals to reinforce ideal early acceleration with speed maintained during the initial acceleration phase (20 m).
  3. Sprinting with 3% BM may benefit athletes requiring a more force dominant F-v profile by improving their external horizontal force production.

 

Link to Publication

 

Acute Study: Forearm Wearable Resistance Effects on Sprint Kinematics and Kinetics

Macadam, Simperingham (13)

 

Purpose Statement:

To compare the effects of WR attached to the forearms on over ground sprint performance in semi-professional male athletes.

 

Introduction:

Twenty-two male amateur youth rugby players performed two 20 m over the ground sprints with and without 2% BM attached to forearms (Figure 14).

Figure 14: WR forearm loading of 2% BM

Key Findings:

  1. No significant decrease in times to 10 m, but significant decreases between 10-20m (-2%).
  2. A significant decrease was found in V0 (-1.4%) and horizontal power output (-5.8%), while a non-significant decrease in theoretical maximum velocity (-4.2%) occurred.
  3. A significant increase in contact time (6.5%) and step length (2.1%), and significant decrease in step frequency (-4.1%) and flight time (-5.3%) were found.

 

Practical Applications:

  1. May reinforce ideal early acceleration with speed maintained during the early acceleration phase (10 m).
  2. 2% BM forearm WR provides sufficient overload of arm action during sprinting without unduly affecting sprinting technique (<6% change).
  3. Forearm WR may be suitable to enhance arm drive mechanics.
  4. An increase in moment of inertia on the arms may alter the transfer of momentum to the body in the arm swing.

 

Link to Publication

 

Acute Study: Effects of forearm wearable resistance on acceleration mechanics in collegiate track sprinters

Uthoff, Nagahara (14)

 

Purpose Statement:

How does forearm loading affect kinetic and kinematic characteristics during sprinting?

 

Introduction:

Arm action during sprinting has commonly been thought of as a coordinative mechanism to overcome rotation of the pelvis as a result of lower limb rotational movements, as well as a mechanism that functions to assist horizontal and vertical propulsion. Arm action contributes up to 22% of the body’s total kinetic energy during block starts. Limited previous literature found that forearm wearable resistance loads >2%BM are required to significantly overload sprinting performance and associated step variables.

  • Fourteen sub-elite male sprinters completed 30m sprints from block starts with and without 2%BM forearm loading (
  • Analysed 4 phases of acceleration: start (steps 1-4), early acceleration (steps 5-8), mid-acceleration (steps 9-12), late acceleration (steps 13-16)
    • Kinetic Variables: performance, step frequency (SF), step length (SL), contact (CT) and flight (FT) time
    • Kinematic Variables: Mean propulsive force, Net horizontal impulse, propulsive impulse (HPH+), braking impulse, vertical impulse (IMPv)

Figure 15: 2% BM forearm loading distributed between both arms; loads evenly placed in a dove-tailed manner

 

Key Findings:

  1. Sprint performance (times) were not significantly altered (p>0.05; -1.38% to -1.75%)
  2. SL (+4.01%, ES=0.15 to 1.93) and HPH+ (+5.48%, ES=-0.30 to 1.88) significantly increased at the start of the sprint (phase 1)
  3. Although SF (-4.86%, ES=-1.69 to -0.14) was lower, both FT (+7.70%, ES=0.02 to 1.56) and IMPv (+4.12%, ES=0.07 to 1.72) were greater during late acceleration with loading

 

Practical Applications:

  1. Forearm WR loading (2% BM) is a good method of overloading arm mechanics during sprinting due to negligible impacts on performance and technique
  2. 2% BM forearm loading during the start phase of acceleration from a block may provide a method for overloading horizontal propulsion, by increasing SL without sacrificing SF
  3. Practitioners should avoid using forearm loading during late acceleration, unless an athlete requires a stimulus which enables more vertical lift in order to reposition their limbs, potentially to minimize over-striding.

 

Link to Publication

 

Acute Study: Force-velocity profile changes with forearm wearable resistance during standing start sprinting

Macadam, Mishra (15)

 

Purpose Statement:

How does forearm loading affect the horizontal force velocity profile of a collegiate male sprinter?

 

Introduction:

Arm mechanics function to maximize sprinting performance. A method of measuring sprint performance is achieved via measuring and athlete’s power and acceleration ability, using a force-velocity profiles. Significant changes in the slope of the F-V profile, along with minimal sprint kinematic changes may elude towards wearable resistance being a training to improve horizontal force during early acceleration of sprinting.

  • Fourteen sub-elite male sprinters completed 30m sprints from split-stance starts with and without 2%BM forearm loading (Figure 15)
  • Analysed force velocity profiles including theoretical horizontal velocity (V0), theoretical horizontal force (F0), horizontal power (PMAX), and the slope of the F-V curve (SFV)

 

Key Findings:

  1. Sprint performance (times) were significantly increased at -10m (+2.7%, ES: 0.54), -20m (+2.1%, ES: 0.57), and -30m (+1.9%, ES: 0.60)
  2. Significantly decreased PMAX was found when loaded (-6.1%, ES: 0.66)

 

Practical Applications:

  1. Sprinting from a split-stance start with forearm WR may be a method to train sprinting performance over the mid- to late- acceleration phases
  2. Sprinting with forearm WR affects the force component of the F-V profile, thus altering power capability of trained sprinters
  3. Forearm WR may be a potential training method for athletes aiming to enhance force/power adaptations during acceleration, from a standing start
  4. Forearm WR during sprinting may affect different athletes different, thus a good understanding of the specific horizontal F-V requirements of the sport/athlete is important prior to utilizing forearm WR.

 

Link to Publication

 

Acute Study: The Effect of Lower Limb Wearable Resistance Location on Sprint Running Step Kinematics

Feser, Macadam (16)

 

Purpose Statement:

How do different WR placement of the leg effect 50 m sprint performance

 

Introduction:

Fourteen track and field athletes performed two 50 m over the ground sprints with and without 2% BM attached to either the thigh or shank (Figure 16). WR was placed and oriented to the most distal position from joint of rotation.

Figure 16: Thigh and shank WR of 2% BM

Key Findings:

  1. Both the thigh and shank WR significantly decreased the maximal velocity achieved (-1.8 to 2%), though 10 m and 50 m sprint times were minimally changed (p > 0.05).
  2. During the acceleration phase, the only significant difference to the unloaded condition was step frequency with shank WR (-2.1%).
  3. During the maximal velocity phase, shank WR significantly changed step frequency (-2.5%), contact time (2.1%), and flight times (3.3%); thigh WR significantly changed step frequency (-1.4%) and contact time (2.9%).

 

Practical Applications:

  1. As slightly greater changes to step kinematics were found throughout both phases of the sprint distance with shank WR, practitioners may wish to utilize this placement for athletes needing to overload the acceleration and maximal velocity phases.
  2. It appears peripheral loading (2% BM) of the thigh and shank can be used to overload step frequency and contact time but not step length and width.

 

Link to Publication

 

 

Acute Study: Acute Spatiotemporal and Muscle Excitation Responses to Wearable Lower Limb Loading During Maximal Velocity Sprinting

Hurst, Kilduff (17)

 

Purpose Statement:

To quantify the mechanical effects of adding WR to the thigh or shank segments during maximal velocity sprinting.

 

Introduction:

Eight university level sprinters performed two 40 m sprints under each condition (unloaded, thigh WR of 1.7% BM, shank WR of 0.6% BM).

 

Key Findings:

  1. There was a possibly small decrease in maximum velocity In both thigh (-1.8%) and shank (-1.4%) conditions, which was associated with a likely small decrease in step frequency (thigh -3.7%, shank -2.3%) and no clear difference in step length (1-1.5%).
  2. There was a likely small increase in contact time with thigh WR (2.5%), and possibly small increases in both flight time (2.8%) and contact time (1.2%) with shank WR.
  3. There were no clear differences in peak muscle excitation (EMG assessment) of the biceps femoris or semitendinosus between conditions.

 

Practical Applications:

  1. As changes in sprint performance were small, WR may provide a suitable high degree of specificity training method to bridge the gap between phases of a periodised training plan.
  2. As there were no clear differences in biceps femoris or semitendinosus EMG muscle activity between the conditions, WR of this magnitude does not increase the excitation demand placed on the hamstrings.

 

Link to Publication

 

Training Study: Thigh Positioned Wearable Resistance Improves 40m Sprint Performance: A Longitudinal Single Case Design Study

Macadam, Nuell (18)

 

Purpose Statement:

To quantify the mechanical changes that occur following a five-week sprint training program with WR attached to the thighs.

 

Introduction:

One male former sprinter (32 years, 72.4 kg and 180.2 cm, 10.90 s 100 m time) undertook a five-week intervention with WR of 2% BM attached to the thighs. The athlete completed two to three sprint session per week in a periodised manner with WR.

 

Key Findings:

  1. Substantially faster times were found at all distances of 10 m (-3.4%), 20 m (-2.5%), 30 m (-2.4%), and 40 m (-2.4%).
  2. Theoretical maximum velocity (1.2%), theoretical measures of horizontal force (7.1%) and maximum power (8.4%) were all substantially increased. Contact times were substantially decreased (-5.5%), while flight times (4.7%) and vertical stiffness (12.9%) were substantially increased

 

Figure 17: Changes in sprint kinematics

Practical Applications:

  1. WR provides a sprint-specific method for rotational overload and subsequent speed specific adaptation with decreases in sprint times being accompanied by increases of sprint mechanical properties, reductions in contact times and increases in vertical stiffness
  2. WR attached to the thigh enables loads to be applied directly to the body that will stress specific sprint movements under the specific demands of an actual sport and competitive environment, without compromising the speed of motion, range of motion and specific skill.

 

Link to Publication

 

Training Study: Thigh Positioned Wearable Resistance Affects Step Frequency, Not Step Length During 50m Sprint-Running

Macadam, Nuell (19)

 

Purpose Statement:

To determine the acute changes in spatio-temporal, impulse, and vertical stiffness variables when 2% BM was attached distally to the thighs during maximal effort sprinting.

 

Introduction:

15 Japanese sprinters performed 2 maximal effort, 50m sprints from block starts under 2 different loading conditions (2%BM and unloaded). Sprint times were measured using timing gates at 10m and 50m. Spatio-temporal, impulse, and vertical stiffness variables were determined from 54 in-ground force platforms (1000Hz) [-1.5m to 50.5m].

  • Step duration: foot strike of one leg to foot strike of the opposite leg
  • Contact time: duration of foot contact with the ground
  • Flight time: duration of no foot contact with the ground
  • Step length: distance between ground contact foot placements for two adjacent steps (L and R) in the A-P direction
  • Step Frequency: Inverse of step duration (1/step duration = 1/s)
  • Step Velocity: step length x step frequency
  • Impulse:
  • Vertical Stiffness:

Figure 18: Wearable Resistance of 2% Body Mass Attached to the Distal Aspect of the Thighs

 

Key Findings:

  1. Thigh WR has a greater effect on step frequency (decreased) than step length, leading to longer contact times.
  2. Thigh WR resulted in 4.8% decrease in net anterior-posterior impulses in steps 5-14 due to an earlier foot-strike, and thus greater braking impulse.
  3. Vertical stiffness was decreased 5.5% between steps 5-14, potentially due to increased flexion at the knee and ankle joints during the support phase (increased contact times.

Practical Applications:

  1. WR provides a sprint-specific method for rotational overload and subsequent speed specific adaptation with decreases in sprint times being accompanied by increases of sprint mechanical properties, reductions in contact times and increases in vertical stiffness
  2. WR may be a training tool to overload net anterior-posterior impulses, resulting in positive adaptations to horizontal force production, to overcome the additional loading. (Teach the sprinter to increase horizontal force production, and decrease braking of each step)
  3. Thigh WR may provide a training stimulus to overload vertical stiffness, effectively overloading the stretch-shortening cycle, to help reduce leg compliance.

 

Link to Publication

 

Agility

Editorial: Wearable Resistance Training for Speed and Agility

Cleary Dolcetti, Cronin (21)

 

Purpose Statement:

How can wearable resistance be a powerful training modality to improve speed and agility, and how it can be used to first coach and then train athletes.

 

Introduction:

Most resistance training exercises are vertically orientated, rather than horizontally or laterally which are principle components of speed and agility. Furthermore, traditional resistance training exercise tend to be slower, less range of motion, and acyclic, where movement is typically cyclic in nature. The importance of the principle of specificity in optimizing transference of training adaptation is important for all athletes, more increasingly so for the elite. WR training involves an external load being applied to segments of the body during movement and is an example of one concept of training specificity. WR has the potential to address limiters to transference such as:

  • Lack of velocity
  • Lack of range of motion
  • Contraction type
  • Metabolic specificity to the activity of interest

 

Argument for Wearable Resistance:

Mechanical

  • WR allows for other ways of developing high forces, through light loads (grams, kilograms) (Figure 20)
  • WR provides a direct rotational overload to the limb of interest and the associated proximal joints and musculature
  • A change in rotational inertia increases the kinetic output of the joint proximal to the location of the added load, with a greater effect when the load is more distal and when the magnitude is increased.

Figure 20: Different methods for the development of force capability

Neural

  • Improving neural efficiency to enhance force capability and movement quality is key for many S&C coaches
  • Adding load to a sports movement would be a suitable strategy for achieving the specificity needed to develop the necessary intramuscular coordination

Metabolic

  • WR provides a metabolic stimulus during sprinting and agility performance, particularly if the activities are repetitive in nature and more reflective of actual competition-specific demands and durations

 

Tips for Wearable Resistance Use

The use of WR in a periodised plan depends on the requirements of the sport and the individual needs of the athlete. The value of WR as a training tool is during specific strength training; when looking to modify the use of traditional resistance training to find more relevant ways to overload the body that re force, speed, and ROM relevant to the sport

 

Individualisation – If the load feels wrong, change it

  • Loads must be first “felt” and then “lifted” (i.e. if the loading is too heavy, unnatural, or uncomfortably orientation, it should be adjusted)
  • Load adjustments should be both user and coach driven

Specificity – Reduce the load not the speed

Progressive Overload – Progress in grams, not kilograms

  • There is an inherent trade-off between load and specificity
  • The load is secondary to the movement
  • Progression can be achieved by moving the same load more distally from the axis of rotation; thus increasing the rotational inertia

Overtraining – Listen to your body

  • Although light, WR is still resistance; high velocity movements are generally MORE fatiguing

 

Link to Publication

 

 

 

 

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