Effects of upper and lower body wearable resistance on spatio-temporal and kinetic parameters during running

Evaluating the Biomechanical Effects and Real-World Usability of a Novel Ankle Exo for Runners

Achilles tendon overuse injuries are common for long-distance runners. Ankle exos (exoskeletons and exosuits) are wearable devices that can reduce Achilles tendon loading and could potentially aid in the rehabilitation or prevention of these injuries by helping to mitigate and control tissue loading. However, most ankle exos are confined to controlled lab testing and are not practical to use in real-world running. Here, we present the design of an unpowered ankle exo aimed at reducing the load on the Achilles tendon during running while also overcoming key usability challenges for runners outside the lab. We fabricated a 500-gram ankle exo prototype that attaches to the outside of a running shoe. We then evaluated the reliability, acceptability, transparency during swing phase, and offloading assistance provided during treadmill and outdoor running tests. We found that the exo prototype reliably assisted 95-99% of running steps during indoor and outdoor tests, was deemed acceptable by more than 80% of runners in terms of comfort and feel, and did not impede natural ankle dorsiflexion during leg swing for 86% of runners. During indoor tests, the exo reduced peak Achilles tendon loads for most participants during running; however, reductions varied considerably, between near zero and 12%, depending on the participant, condition (speed and slope) and the precise tendon load metric used. This next-generation ankle exo concept could open new possibilities for longitudinal and real-world research on runners, or when transitioning into the return-to-sport phase after an Achilles tendon injury.

Impedance for Assistance: Upper-Limb Assistive Soft Robotic Suit Using Linked-Layer Jamming Mechanisms

Wearable robots, especially those composed of soft materials, are increasingly attracting interest due to their comfort, ease of donning and doffing, and their ability to provide assistance across various applications. In wearable robotics, striking a balance between ensuring low impedance for wearer comfort and providing sufficient assistive force is a notable design challenge. In this study, we propose exploiting impedance variation in accordance with the types of muscle contraction in the human body. Particularly in eccentric muscle contraction, the impedance can help reduce the muscular load, since it exerts force in the same direction as the muscles. To utilize the relation, we proposed a linked-layer jamming mechanism, which adjusts its impedance largely in various directions. This mechanism allows not only a broad variable range of impedance in multiple rotation directions but also directional torque design, even when equipped in human multi-degree-of-freedom (DoF) joints. By constructing a wearable robot prototype equipped with the proposed linked-layer jamming mechanisms, the effectiveness of this impedance-based assistance approach was confirmed through experiments. The findings from this study present new possibilities in wearable robot design, showing that suitably amplified impedance can assist human motion, potentially enhancing task efficiency and lowering injury risk. This work thus offers a new perspective for researchers in the field of wearable robots, demonstrating that impedance, often minimized in existing designs, can be utilized beneficially when properly amplified.

Acute effects of lower limb wearable resistance on horizontal deceleration and change of direction biomechanics

This study aimed to investigate the acute effects of lower limb wearable resistance on maximal horizontal deceleration biomechanics, across two different assessments. Twenty recreationally trained team sport athletes performed acceleration to deceleration assessments (ADA), and 5-0-5 change of direction (COD) tests across three load conditions (unloaded, 2% of BW, 4% of body weight (BW)), with load attached to the anterior and posterior thighs and shanks. Linear mixed effect models with participant ID as the random effect, and load condition as the fixed effect were used to study load-specific biomechanical differences in deceleration mechanics across both tests. Primary study findings indicate that for the ADA, in the 4% BW condition, participants exhibited significantly greater degrees of Avg Approach Momentum, as well as significant reductions in deceleration phase center of mass (COM) drop, and Avg Brake Step ground contact deceleration (GCD) in both the 2% BW, and 4% BW condition, compared to the unloaded condition. In the 5-0-5 tests, participants experienced significant reductions in Avg Approach Velocity, Avg deceleration (DEC), and Stopping Time in the 4% BW condition compared to the unloaded condition. Similar to the ADA test, participants also experienced significant reductions in Avg Brake Step GCD in both the 2% BW and 4% BW conditions, and significant increases in Avg Approach Momentum in the 4% BW condition, compared to the unloaded condition. Therefore, findings suggest that based on the test, and metric of interest, the addition of lower limb wearable resistance led to acute differences in maximal horizontal deceleration biomechanics. However, future investigations are warranted to further explore if the use of lower limb wearable resistance could present as an effective training tool in enhancing athlete's horizontal deceleration and change of direction performance.

Acute locomotor, heart rate and neuromuscular responses to added wearable resistance during soccer-specific training

PURPOSE

Investigate acute locomotor, internal (heart rate (HR) and ratings of perceived exertion (RPE)) and neuromuscular responses to using wearable resistance loading for soccer-specific training.

METHODS

Twenty-six footballers from a French 5th division team completed a 9-week parallel-group training intervention (intervention group: n = 14, control: n = 12). The intervention group trained with wearable resistance (200-g on each posterior, distal-calf) for full-training sessions on Day + 2, D + 4 and unloaded on D + 5. Between-group differences in locomotor (GPS) and internal load were analyzed for full-training sessions and game simulation drills. Neuromuscular status was evaluated using pre- and post-training box-to-box runs. Data were analyzed using linear mixed-modelling, effect size ±90% confidence limits (ES ± 90%CL) and magnitude-based decisions.

RESULTS

Full-training sessions: Relative to the control, the wearable resistance group showed greater total distance (ES [lower, upper limits]: 0.25 [0.06, 0.44]), sprint distance (0.27 [0.08, 0.46]) and mechanical work (0.32 [0.13, 0.51]). Small game simulation (<190 m2/player): wearable resistance group showed small decreases in mechanical work (0.45 [0.14, 0.76]) and moderately lower average HR (0.68 [0.02, 1.34]). Large game simulation (>190 m2/player): no meaningful between-group differences were observed for all variables. Training induced small to moderate neuromuscular fatigue increases during post-training compared to pre-training box-to-box runs for both groups (Wearable resistance: 0.46 [0.31, 0.61], Control: 0.73 [0.53, 0.93]).

CONCLUSION

For full training, wearable resistance induced higher locomotor responses, without affecting internal responses. Locomotor and internal outputs varied in response to game simulation size. Football-specific training with wearable resistance did not impact neuromuscular status differently than unloaded training.

Impacts of Wearable Resistance Placement on Running Efficiency Assessed by Wearable Sensors: A Pilot Study

Wearable resistance training is widely applied to enhance running performance, but how different placements of wearable resistance across various body parts influence running efficiency remains unclear. This study aimed to explore the impacts of wearable resistance placement on running efficiency by comparing five running conditions: no load, and an additional 10% load of individual body mass on the trunk, forearms, lower legs, and a combination of these areas. Running efficiency was assessed through biomechanical (spatiotemporal, kinematic, and kinetic) variables using acceleration-based wearable sensors placed on the shoes of 15 recreational male runners (20.3 ± 1.23 years) during treadmill running in a randomized order. The main findings indicate distinct effects of different load distributions on specific spatiotemporal variables (contact time, flight time, and flight ratio, p ≤ 0.001) and kinematic variables (footstrike type, p < 0.001). Specifically, adding loads to the lower legs produces effects similar to running with no load: shorter contact time, longer flight time, and a higher flight ratio compared to other load conditions. Moreover, lower leg loads result in a forefoot strike, unlike the midfoot strike seen in other conditions. These findings suggest that lower leg loads enhance running efficiency more than loads on other parts of the body.

The use of wearable resistance and weighted vest for sprint performance and kinematics: a systematic review and meta-analysis

Wearable resistance (WR) and weighted vests (WV) can be used in almost all training conditions to enhance sprint performance; however, positioning and additional mass are different in WV and WR strategies, affecting performance and kinematics differently. We aimed to systematically review the literature, searching for intervention studies that reported the acute or chronic kinematic and performance impact of WV and WR and comparing them. We analyzed Pubmed, Embase, Scopus, and SPORTDiscuss databases for longitudinal and cross-over studies investigating sprint performance or kinematics using an inverse-variance with a random-effect method for meta-analysis. After the eligibility assessment, 25 studies were included in the meta-analysis. Cross-over WR and WV studies found significantly higher sprint times and higher ground contact times (CT) compared to unloaded (UL) conditions. However, WR presented a lower step frequency (SF) compared to UL, whereas WV presented a lower step length (SL). Only one study investigated the chronic adaptations for WR, indicating a superiority of the WR group on sprint time compared to the control group. However, no difference was found chronically for WV regarding sprint time, CT, and flight time (FT). Our findings suggest that using WV and WR in field sports demonstrates overload sprint gesture through kinematic changes, however, WR can be more suitable for SF-reliant athletes and WV for SL-reliant athletes. Although promising for chronic performance improvement, coaches and athletes should carefully consider WV and WR use since there is no supporting evidence that WV or WR will impact sprint performance, CT, and FT.

Effects of Different Wearable Resistance Placements on Running Stability

Stability during running has been recognized as a crucial factor contributing to running performance. This study aimed to investigate the effects of wearable equipment containing external loads on different body parts on running stability. Fifteen recreational male runners (20.27 ± 1.23 years, age range 19-22 years) participated in five treadmill running conditions, including running without loads and running with loads equivalent to 10% of individual body weight placed on four different body positions: forearms, lower legs, trunk, and a combination of all three (forearms, lower legs, and trunk). A tri-axial accelerometer-based smartphone sensor was attached to the participants' lumbar spine (L5) to record body accelerations. The largest Lyapunov exponent (LyE) was applied to individual acceleration data as a measure of local dynamic stability, where higher LyE values suggest lower stability. The effects of load distribution appear in the mediolateral (ML) direction. Specifically, running with loads on the lower legs resulted in a lower LyE_ML value compared to running without loads (p = 0.001) and running with loads on the forearms (p < 0.001), trunk (p = 0.001), and combined segments (p = 0.005). These findings suggest that running with loads on the lower legs enhances side-to-side local dynamic stability, providing valuable insights for training.

Acute changes in acceleration phase sprint biomechanics with lower body wearable resistance

The aim of this acute cross-sectional study was to quantify the kinematic and kinetic changes that occur during sprint acceleration when lower body WR is worn. Fifteen male rugby athletes (19 years; 181 cm; 91 kg) were assessed during maximal effort over-ground and treadmill sprinting over 20 m under three different loading conditions: 0%, 3% and 5% body mass (BM) added weight attached to the lower body. Treadmill data provided a convenient estimate of kinetic changes in the absence of in-ground force plates. The loaded conditions resulted in significantly increased ground contact time (5 to 6%) and decreased step frequency (-2 to -3%) during sprint accelerations (effect size = 0.32-0.72). Moderate WR loading (3% BM) resulted in increased (9%; effect size = 0.66) theoretical maximum horizontal force (relative to BM) and unchanged 20 m sprint times (p > 0.05). Heavier WR loading (5% BM) resulted in a significant decrease (-4%) in vertical ground reaction forces (relative to total system mass) and slower (1 to 2%) 20 m sprint times (effect size = 0.38-0.70). Lower body WR loading up to 5% BM can provide specific sprint training overload, while affecting sprint acceleration biomechanics by ≤ 6%.

Effects of different hydration supports on stride kinematics, comfort, and impact accelerations during running

BACKGROUND

Different supports for hydration can influence total body mass and affect running biomechanics.

RESEARCH QUESTION

Do different hydration supports affect the perceived exertion and comfort, stride kinematics, and impact accelerations during running?

METHODS

This was a crossover study design. Thirteen trail runners completed a treadmill running test divided into four different durations and randomized hydration supports conditions, lasting 8 min each at moderate intensity: A) waist bag (0.84 kg); B) medium load backpack (0.84 kg); C) full load backpack (3.40 kg); and D) a control condition without water support. Impact accelerations were measured for 30 s in 4, 6, and 8 min. The rate of perceived exertion and heart rate were registered on minutes 4 and 8. At the last minute of each condition, comfort perception was registered RESULTS AND SIGNIFICANCE: No condition affected the stride kinematics. Full load backpack condition reduced head acceleration peak (-0.21 g; p = 0.04; ES=0.4) and head acceleration magnitude (-0.23 g; p = 0.03; ES=0.4), and increased shock attenuation (3.08 g; p = 0.04; ES=0.3). It also elicited higher perceived exertion (p < 0.05; ES>0.8) being considered heavier (p < 0.01; ES > 1.1). The waist bag condition was more comfortable in terms of noise (p = 0.006; ES=1.3) and humidity/heat (p = 0.001; ES=0.8). The waist bag was the most comfortable support. On the other hand, the full backpack elicited lower comfort and was the only generating compensatory adjustments. These results may help to improve design of full load backpack aiming at comfort for runners.

The assessment of a novel lower body resistance garment as a mechanism to increase the training stimulus during running: a randomised cross-over study

BACKGROUND

This study examined the physiological and perceived impact of wearing a novel lower body resistance garment during exercise and recovery.

METHODS

Using a randomised cross-over design, 15 recreationally-active males performed 2 × 10-min steady-state runs followed by a 10-min passive recovery with concomitant monitoring of oxygen consumption (V̇O2), heart rate (HR) and rating of perceived exertion (RPE; exercise portion only), wearing either the resistance garment (experimental) or running shorts (control).

RESULTS

During exercise, there was a trend for V̇O2 and RPE to be higher (4.5% and 7.7% respectively) in experimental than control (V̇O2: r = 0.24, p > 0.05; RPE: r = 0.32, p > 0.05) and for HR to be lower (- 0.4%, r = - 0.05, p > 0.05). During recovery, V̇O2 and HR tended to be lower (4.7% and 4.3% respectively) in experimental than control (V̇O2: r = - 0.32, p > 0.05; HR: r = - 0.27, p > 0.05).

CONCLUSIONS

Though effects were trivial to small, and not statistically significant, these findings provide proof of concept and suggest that this garment design may increase the training stimulus during running and aid post-exercise recovery.

Kinetic and Kinematic Effects of Asymmetrical Loading of the Lower Limb During High-Speed Running

CONTEXT

Light lower-limb wearable resistance has little effect on running biomechanics. However, asymmetrical wearable resistance may potentially alter the kinetics and kinematics of high speed, enabling greater loading or unloading of an injured or rehabilitative lower limb.

DESIGN

A cross-sectional study design was used to quantify the influence of asymmetric calf loading on the kinematics and kinetics during 90% maximum sprinting velocity.

METHODS

Following a familiarization session, 12 (male = 7 and female = 5) physically active volunteers ran at 90% of maximal velocity. In random order, participants ran with zero (0) wearable resistance and with loads of 300 g (L300) and 600 g (L600) fixed to one shank. A nonmotorized treadmill quantified vertical and horizontal kinetics and step kinematics. The kinetics and kinematics of the loaded (L0, L300, and L600) and unloaded (UL; UL0, UL300, and UL600) limbs were compared.

RESULTS

Vertical step ground reaction force of the loaded limb tended to increase between unloaded and 300 and 600 conditions (effect size [ES] = 0.48 to 0.76, all P ≤ .12), while the horizontal step force of the UL tended to decrease (ES = 0.54 to 1.32, all P ≤ .09) with greater external loading. Step length increased in the UL in 0 versus 300 and 600 conditions (ES = 0.60 to 0.70, all P ≤ .06). Step frequency decreased in the ULs in unloaded versus 300 and 600 conditions (ES = 0.73 to 1.10, all P ≤ .03). Mean step velocity tended to be greater in the ULs than the 300 and 600 conditions (ES = 0.52 to 1.01, all P ≤ .10). Only 4 of 16 variables were significantly different between the 300 and 600 conditions.

CONCLUSIONS

Asymmetrical shank resistance could be used during high-speed running to reduce or increase the kinetic loading of an injured/rehabilitative limb during return to play protocols. Asymmetrical wearable resistance could also be used to alter step kinematics in runners with known asymmetries. Finally, meaningful alterations in high-speed running biomechanics can be achieved with only 300 g of shank loading.

Effects of lower limb light-weight wearable resistance on running biomechanics

Wearable resistance allows individualized loading for sport specific movements and can lead to specific strength adaptations benefiting the athlete. The objective was to determine biomechanical changes during running with lower limb light-weight wearable resistance. Fourteen participants (age: 28 ± 4 years; height: 180 ± 8 cm; body mass: 77 ± 6 kg) wore shorts and calf sleeves of a compression suit allowing attachment of light loads. Participants completed four times two mins 20-m over-ground shuttle running bouts at 3.3 m*s^-1 alternated by three mins rest. The first running bout was unloaded and the other three bouts were under randomised loaded conditions (1%, 3% and 5% additional loading of the individual body mass). 3D motion cameras and force plates recorded kinematic and kinetic data at the midpoint of each 20-m shuttle. Friedman-test for repeated measures and linear mixed effect model analysis were used to determine differences between the loading conditions (α = 0.05). Increased peak vertical ground reaction force (2.7 N/kg to 2.74 N/kg), ground contact time (0.20 s to 0.21 s) and decreased step length (1.49 m to 1.45 m) were found with additional 5 % body mass loading compared to unloaded running (0.001 > p < 0.007). Marginally more knee flexion and hip extension and less plantarflexion was seen with higher loading. Differences in the assessed parameters were present between each loading condition but accompanied by subject variability. Further studies, also examining long term effects, should be conducted to further inform use of this training tool.