Biomechanics of Locomotion
Introduction to Sport & Exercise Physiology
Learning Outcomes
By the end of this lecture, students should be able to:
Understand the main biomechanical differences between forward (FW) and backward (BW) locomotion.
Analyze how these differences influence various physiological parameters.
Evaluate why backward locomotion is a viable option for individuals with knee or posterior chain injuries.
Assess how backward locomotion affects different biomotor abilities in various population groups.
Identify potential practical applications of backward locomotion in sport and exercise settings.
Biomechanics of Locomotion
Differences Between Forward and Backward Locomotion
Backward Locomotion
Joint Mechanics:
Ankle: Plantarflexion occurs during touchdown.
Knee: Involves concentric muscle contractions, resulting in less impact.
Hips: Display greater degree of flexion leading to lower range of motion (ROM).
Stride Patterns:
Stride Length (SL): Shorter.
Stride Frequency (SF): Higher.
Stance Phase/Support Time: Longer duration.
Forward Locomotion
Joint Mechanics:
Ankle: Dorsiflexion occurs during touchdown.
Knee: Loaded primarily through eccentric muscle contraction.
Hips: Exhibit a greater degree of extension.
Stride Patterns:
Stride Length (SL): Longer.
Stride Frequency (SF): Shorter.
Stance Phase/Support Time: Shorter duration.
Physiological Parameters
1. Muscle Activation
Backward Locomotion
Exhibits greater concentric contraction during the touchdown phase of the gait cycle.
Also shows greater isometric muscle contractions (definition: involves muscle contraction without any visible movement of the joint. The muscle length remains constant, and you’re holding a position against resistance) during the stance/support phase.
Reduction in the use of posterior chain musculature, leading to increased activity of the vastus lateralis, while showing reduced activity of hamstrings and glutes (Grasso, Bianchi, and Lacquaniti, 1998).
Enhanced recruitment of the tibialis anterior during the swing phase, leading to a greater range of motion around the ankle joint, possibly aiding in plantar flexion recovery.
Forward Locomotion
Mostly involves eccentric contractions of the quadriceps with more reliance on posterior chain musculature.
Increased usage of the gastrocnemius muscle during the toe-off phase.
2. Neuromuscular Demands
Backward walking is not merely the reversal of forward walking; it necessitates distinct motor commands and sensory feedback integration (Grasso et al., 1998).
Muscle activation patterns differ from those seen in forward locomotion:
Backward locomotion requires the reorganization of muscle synergies, highlighting the significance of central pattern generators (CPGs) and sensory feedback mechanisms.
Central Pattern Generators (CPGs): Neural circuits in the brain and spinal cord responsible for generating coordinated and rhythmic limb movements without sensory input or conscious control.
3. Balance and Proprioception
Backward exercise necessitates locomotion without visual sensory inputs.
The central nervous system (CNS) must depend on proprioception and vestibular inputs to understand the environment, increasing attentional demands with the novelty of the task.
This increased demand translates to heightened balance requirements owing to variations in stride length and frequency.
4. Cardiorespiratory Demands & Energy Expenditure
Research Findings
Comparison of Responses: According to Flynn et al. (1994) at matched speeds:
BW walking reflects 60% of FW peak oxygen consumption.
BW running requires 84% of FW peak oxygen consumption, with heart rates during BW walking and running being 10 bpm higher than during FW counterparts.
Further analysis by Hooper et al. (2004) indicated:
BW walking at inclines of 5%, 7.5%, and 10% resulted in 17% to 20% higher heart rates and increased oxygen consumption compared to FW walking.
Energy Cost of Backward Running at Positive Gradients: Bellistri et al. (2015) found:
Energy cost for BW running was 35% higher than for FW running due to increased stride frequency.
Specific energy expenditures were noted as:
BW running:
FW running:
Mean EMG activity was consistently higher during BW compared to FW locomotion at given speeds, indicating heightened energy expenditure (Grasso, Bianchi, and Lacquaniti, 1998).
Integrating Biomechanics and Physiology
Concentric muscle contractions during BW result in a higher metabolic cost relative to eccentric contractions.
During eccentric contractions, there are fewer motor units (MUs) recruited and more efficient cross-bridge mechanics, with passive structures aiding force output.
Increased stride frequency and decreased stride length also contribute to higher energy output observed in BW locomotion.
Connections to Injury
Since BW locomotion involves less eccentric muscle contractions, it applies less mechanical tension to tendons and ligaments at equal movement speeds, thus minimizing the likelihood of overstretching the anterior cruciate ligament (ACL) (Flynn et al., 1991 and 1993).
The dynamics lead to significant benefits for individuals recovering from hamstring strains and other related injuries, as it maintains lower hip extension, resulting in decreased activation of hamstrings and promoting gluteal muscle engagement.
Potential Benefits of Backward Running
Enhances fitness levels and improves quickness.
Facilitates balance and proprioceptive strength.
Strengthens muscles and optimizes the interaction between agonist and antagonist muscles.
Contributes positively to posture training by incorporating variability principles.
Metabolic Transition Speed
Definition: Transition speed reflects the changing point at which a person begins to run instead of walking during locomotion.
This phenomenon is theorized to occur at distances that minimize metabolic energy expenses.
Contradicting Evidence: Other studies (Hreljac, 1993; Diedrich & Warren, 1995; Terblanche et al. 2003) suggest that spontaneous transition speeds may occur at speeds even before metabolic transition speeds manifest.
Triggering factors may involve biomechanical attributes like limb length, experience, locomotion purpose, and exercise exertion perceptions.
Studies on Metabolic Transition Speed
“The Metabolic Transition Speed Between Backward Walking and Running” – Terblanche et al. (2003) utilized 18 participants to analyze variations and adaptations during transition speed tests on a treadmill.
The research provides valuable insights on average transition speeds marking the change from walking to running for both BW and FW locomotion.
Conclusions on Transition Speeds
Walking-to-running transitions in FW locomotion do not correlate with metabolic cost but rather with perceptions of effort.
Metabolic transition speed for BW is notably lower, suggesting individuals commence running BW before it is energetically economical, primarily due to peripheral feedback mechanisms detecting muscle inefficiency.
Practical Applications of Backward Exercise
Backward training has surfaced substantial positive effects on different population groups, as evidenced by qualitative and quantitative research studies.
General Health and Fitness
Study on Young Women
“The effect of backward locomotion training on body composition and cardiorespiratory fitness” (Terblanche et al., 2005) focused on young women (ages 18 to 21) to observe accompanying changes post a 6-week BW training program.
Results showcased significant improvements in body composition measures and cardiorespiratory fitness metrics compared to a control group.
Participants noted improved performance in forward shuttle runs and overall training adaptations, advocating for BW training's efficacy in promoting fat loss.
Applications for Female Athletes in Court-Sports
Training Impact on Netball Players
“The Effect of Backward Training on Speed, Agility, and Power of Netball Players” (Terblanche et al., 2009) elucidated benefits among 20 provincial-level netball players who engaged in backward training.
Program length: 8 weeks with specific exercises aimed at improving agility and performance in game-like scenarios. Results indicated substantial improvement in agility and balance, even if speed and power demonstrated limited enhancement.
Young Male Athletes
Uthoff et al. (2018) studied 67 male athletes aged 13 to 15 across an 8-week training regimen comparing BW and FW running on speed and power measurement.
Findings confirmed that BW running demonstrated considerable transfer benefits to FW running performance, improving important performance metrics like speed and vertical jump heights as well as leg stiffness.
Rehabilitation
Knee Rehabilitation Programs
“The Merits of Backward Locomotion Training in Knee Rehabilitation Programs” discussed potential implications of BW training in rehabilitating knee injuries (Terblanche & Brink, 2010).
Focused on critical dimensions such as improving aerobic capacity, muscle strength, dynamic balance, and flexibility in recovery protocols.
Results reinforced BW training's strength to foster improved leg strength and power, along with increasing overall flexibility, enabling athletes to return to sports better conditioned post-injury.
Recap of Benefits
Health Benefits
Increased calorie burn in shorter sessions, reduced boredom risks, and lower injury potential.
Athletic Advantages
As an alternative training modality, it aids in practicing sport-specific skills while minimizing injury risks. The identified populations that may benefit from BW training include post-surgical knee patients, individuals with various muscle strains, lower extremity injuries, sprained ankles, shin splints patients, and athletes looking for low-impact cross-training options.
This comprehensive overview highlights the critical areas of backward locomotion, its biomechanical and physiological implications, and its diverse practical applications in health, fitness, sports training, and rehabilitation. The notes incorporate detailed assessments, research findings, and integration of various methodologies to enhance understanding of backward exercise in multiple contexts.