Strength can be defined simply as the ability to express force. With that being said, strength is often a requisite necessity to express power (P= F * v). Explosive movements, with or without load, are effective modalities to enhance power. This study out of Cal State Fullerton was conducted with the objective to compare the effects of kettlebell swings vs explosive barbell deadlifts on strength and power.
“It has previously been shown that kettlebell swing training improves rapid lower body force production, but not peak force as much as traditional weightlifting movements (Lake & Lauder, 2012; Otto et al., 2012). Results such as these are no surprise considering the kettlebell lacks the capacity for high loads in comparison to a loaded barbell.” As we consider the nature of various team sports, it may be rational to suggest that rate of force development could be more crucial than peak force production.
Subjects: 31 recreationally trained males (age = 23.13 ± 2.38 years, height = 175.52 ± 6.66 cm, weight = 83.97 ± 13.85 kg) who are familiar with both the kettlebell swing and barbell deadlift. The researchers provided a familiarization week for all participants, consisting of two sessions of 3 x 5 for each movement with cueing.
Methods: Participants were randomly assigned to four weeks of either kettlebell swing (KBG) or explosive deadlift (EDLG) training. Before and after the 4-week training period, the following outcome measures were recorded: counter-movement vertical jump (CMJ), maximal isometric mid-thigh pull (IMTP), and 1RM deadlift. Both training protocols followed a frequency of two days/week with 48-72 hours between sessions. 1RM deadlift testing was done with wrist straps to avoid any potential limitations exposed by grip strength. IMTP was done on a force plate, with a knee angle 125-135°, emulating the second pull of the snatch exercise. From this data, subjects used 10-12.5% of their peak delta force produced for a prescribed load for kettlebell swings.
The 4-week training period followed a linear periodization model. The KBG used 4 x 5 in weeks 2-3 with a load of 10% peak delta force from IMTP, and then a load increase to 12.5% IMTP in weeks 4-5 using a 6 x 4. The EDLG used a “…barbell loaded with 30%-40% of their 1RM as previous research has shown peak power readings at this intensity with this specific exercise (Kaneko, Fuchimoto, Toji, & Suei, 1983; Swinton et al., 2011).” Researchers were cueing maximal velocity for both groups, while retaining sound mechanics.
Results: “The main findings were increases in 1RM deadlift, and vertical jump height for both training groups which may be due to a combination of neural and biomechanical adaptations following periodized velocity specific resistance training (Hill, 1938; Kaneko et al., 1983; Tillin, Pain, & Folland, 2012; Wilson, Newton, Murphy, & Humphries, 1993).”
We know that faster movements enhance velocity and slow/heavier movements enhance strength, as previously defined by McBride, Triplett-McBride, Davie, & Newton (2002). Previous literature has shown that strength training enhances power. “Adams found that training with 70- 100%1RM loads increased power of the vertical jump (Adams et al., 1992).” Unexpectedly, the KBG and EDLG enhanced their 1RM deadlift similarly (8.2kg and 10kg, respectively); showing that power/speed training can increase the expression of strength. This suggests the opposite of previously literature, showing the relationship may work both ways. “There are a number of reasons why this could have occurred with the most likely explanation being greater neural activation.” It is implied that with the low loads used, the rapid velocities may have induced increased motor unit activity.
Similar to the findings of this study, “Kettlebell exercise has been found to increase 1RM back squat, 1RM power clean, 3RM bench press, and 3RM clean and jerk (Aagaard et al., 2002; Manocchia et al., 2013).”
Take-home Point: “Both the KBG and EDLG improved explosively in the vertical jump and forcefully in the deadlift.”As shown with this particular study, “… power and strength training affect each other positively (Aagaard et al., 2002; Adams et al., 1992; Hill, 1938).”
In future years we hope to learn how to further optimize periodization techniques by eliciting strength and power adaptations from a variety of load/set/rep schemes.
Chris Beardsley seems to consume more literature than an entire department. If that’s not enough, his infographics summarize such exceptionally. His recent article found here does a tremendous job explaining recovery and skeletal muscle damage- without generic words that we don’t really understand but tend to keep saying. This short read is very informative. Please check it out for yourself if you find the below points interesting.
What is recovery? “The time it takes for our ability to produce force to return to pre-workout levels is called “strength recovery” and is often taken as the best available measure of whether we have “recovered” from a workout or not.” Neuromuscular fatigue can be a result of one or more of the following three factors:
Peripheral Fatigue: “Peripheral fatigue can include a transitory accumulation of metabolites, altered calcium and sodium-potassium pump functions, and a decrease in intra-muscular glycogen.”
Central Fatigue: “Central fatigue is defined as an impairment in the ability to activate a muscle voluntarily. We can measure this using the interpolated twitch method, which involves comparing the ability of a muscle to produce force in voluntary and involuntary (electrically-stimulated) contractions.”
Muscle Damage: “The damage can occur to the extracellular matrix, causing it to pull away from around the muscle fiber, as well as to the muscle fibers themselves, most commonly to the Z disks that link one sarcomere to the next, and to the sarcolemma that surrounds the fiber.”
“Muscle damage is increased by higher volumes, a closer proximity to failure, longer duration (isometric) contractions, heavier loads, larger ranges of motion, a more elongated muscle, and by using a constant load rather than accommodating resistance.”
“To accelerate recovery from a strength training workout, bodybuilders, strength athletes, and team sports athletes must minimize muscle damage. Clearly, this requires managing the factors that cause muscle damage within the workout, which are: (1) muscle force, (2) fatigue, (3) time under tension, and (4) exercise familiarity.”
On preventing muscle damage: “Conversely, only high muscle forces are required to produce gains in maximum strength, so strength athletes can compromise on the other factors that produce muscle damage in order to improve the rate of strength recovery. Team sports athletes can focus on developing high-velocity strength using light loads and fast bar speeds, which causes no muscle damage at all.”
Notice below a previous infographic Chris posted exemplifying that a starting a strength training program with a session of damaging eccentric exercise did not improve strength gains in untrained individuals.
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