Lactate (also called lactic acid) has traditionally been believed to be a metabolite that is produced only during high-intensity exercise, and which is involved in fatigue. Neither of these beliefs are true.
Although lactate was originally termed a waste product, and was blamed for muscular fatigue, it is now believed to function more as a fuel and also as a hormone.
This new, alternative hypothesis suggests that delayed onset muscle soreness is not caused by inflammation, but instead by minor damage to the nerve endings within muscle spindles.
This study confirms the findings of earlier ones. The main muscles trained by the squat (whether half or full) are the single-joint quadriceps, the adductors, and the gluteus maximus. The squat does not train the hamstrings or the rectus femoris. Use other exercises too.
Tendons respond in different ways to strength training, periods of unloading, and tendinopathy. This review summarized the cellular and molecular effects, as well as the mechanical effects.
Heavy strength training tends to increase maximum strength more than speed, and fast movement training tends to increase speed more than maximum strength. These different effects appear to result from different adaptations. But what causes these adaptations to happen?
Even though we might prefer to train movements and not muscles, it is the adaptations in the muscles (or motor units) that allow us to ↑ force production in sporting movements, and thereby ↑ athletic performance.
CNS fatigue is often associated with heavy strength training using multi-joint exercises (like deadlifts). Yet, the research is very clear that CNS fatigue is greater after long-duration, low-intensity exercise than after short-duration, high-intensity exercise.
An increase in maximum strength is not itself an adaptation, it is the result of multiple adaptations. Understanding this allows us to target the individual, specific adaptations that contribute to strength gains more effectively.
Many experts argue we should reduce asymmetry of movement, in order to improve performance and reduce the risk of injury. But this new study shows that asymmetry during sprinting is very common in high-level sprinters, and is unrelated to both performance and injury risk
Training too frequently can be counterproductive because of central nervous system (CNS) fatigue resulting from muscle damage caused by the previous workout.
Downhill running exercise causes adaptations that are very similar to strength training, including increases in muscle cross-sectional area and fascicle length (and probably also the ability to recruit more motor units).
Tendons adapt to exercise, often by increasing in size and stiffness. Importantly, the increases in stiffness seem to be unrelated to the increases in size, which suggests that they occur due to changes in material properties, not by the addition of more collagen to the tendon.
Tendons adapt to exercise, often by increasing in size and stiffness. Interestingly, aerobic exercise often increases tendon size but it does not always increase tendon stiffness (which is the exact opposite of strength training).
When the large majority of the muscle fibers in a muscle do not receive any mechanical loading for 3 days, there are substantial losses in muscle mass. This is not prevented by consuming more dietary protein.
During a strength training workout, fatigue accumulates. This fatigue [1] impairs the hypertrophy caused by later sets, and [2] causes post-workout fatigue. Both of these effects are greater when training with lighter loads.
Athletes with more fast twitch fibers take longer to recover from a workout, due to impairments in both sarcolemmal excitability (from damage to the cell membrane) and excitation-contraction coupling function.
See more in the next S&C Research Review:
A lack of sleep ↑ inflammatory mediators that contribute to reduced exercise performance by increasing the level of perceived effort (= CNS fatigue). This may be a mechanism through which many lifestyle factors affect the rate of workout recovery.
The rectus femoris does not grow after squat training, and its distal region grows most effectively after knee extension training. Indeed, previous research has shown that the proximal region of the rectus femoris behaves more as a hip flexor than as a knee extensor.
New research has shown us that loads for strength training can now be classified into four categories, which each have different characteristics.
1️⃣ Heavy
2️⃣ Moderate
3️⃣ Light
4️⃣ Very light
During hip extension, the gluteus maximus displays greater activation when the abdominals are braced compared to when they are not braced. This may be because of the greater stability that this affords to the hip joint.
To understand how strength training produces adaptations, it is important to have a physiological model that can accurately predict at least some of the effects of different strength training programs. Here is a model that explains the effects of fatigue during maximal efforts.
Here is a simple process to follow, to help you be more mindful of the four important S&C principles when writing a training program.
Alarmingly, deliberately making use of S&C principles produces surprisingly different results many common recommendations...
Exercises that we perform first in a workout tend to produce the greatest effects, while exercises that we do last tend to cause the smallest effects. This is most likely due to the accumulation of central nervous system fatigue over the course of the workout.
All of the hip adductors double as either hip flexors (adductor brevis, adductor longus, pectineus, and gracilis) or hip extensors (the adductor magnus), and so are actually more relevant to sprint running than the more frequently-trained quadriceps...
Muscles are motors, and we can either tune them to produce more force at slow velocities (against heavy loads) or at fast velocities (against light loads). The adaptations that lead to increased force at slow and fast speeds are different.
We can ↑ mechanical loading (and muscle growth) without ↑ muscle damage, and similarly muscle damage can be ↑ without ↑ muscle growth.
Choosing the right training variables may therefore allow us to ↑ training frequency, and thereby achieve faster hypertrophy
When training for hypertrophy, volume is not the number of sets or reps that you do. It is the number of stimulating reps that you do. These are not the same thing!
Stiffness is the ability to resist deformation by an external load. Stiff objects or systems require a lot of force to change their length. Stiffness can be measured during human movements, but more is not always better.
An increase in maximum speed is not itself an adaptation, it is the result of multiple adaptations. Understanding this allows us to target the individual, specific adaptations that contribute to speed gains more effectively.
Nordics improve sprinting performance, which is not really that surprising if you think about how eccentric training increases active stiffness, and therefore the ability to store strain energy
If we stop strength training, we lose our hard-earned gains in strength gradually as the adaptations reverse. Gains in muscle size are lost most quickly, followed by gains in tendon stiffness, while gains in voluntary activation are lost most slowly.
This important new study shows that a 5-minute period of low-intensity, active recovery immediately after a bout of maximal effort exercise causes faster recovery over the 30-minute period immediately after exercise than a similar 5-minute period of passive recovery.
Low muscle glycogen may cause fatigue not by failing to provide the necessary fuel (as is often assumed) but rather by increasing the amount of calcium ion-related fatigue.
One of the negative effects of strength training (yes, such things do exist!) is the conversion of extremely fast type IIX fibers into moderately fast type IIA fibers. This study casts light on the process by which this conversion occurs.
Current research suggests that untrained people find it harder to activate muscles during eccentric contractions because of inhibition at the spinal level. Training reduces this inhibition, and allows us to express a higher level of force.
Heavy, moderate, and light load strength training can all be used effectively for gaining muscle size, and generally cause similar results. However, there may be a slight benefit of using heavier weights, especially for more advanced lifters.
Importantly, increasing training volume causes more hypertrophy (up to a point) and more muscle damage (especially after a certain point). Understanding these two relationships is key to programming for bodybuilding.
Ice is commonly applied to muscles after muscle-damaging exercise, but it may actually alter the repair process negatively, delaying the onset of the inflammatory and satellite cell responses.
The accumulation of too much fatigue during the practice of sporting movements (such as sprinting and jumping) may inhibit the learning of such motor skills
Excessive strength training frequency is associated with reduced hypertrophy because the post-workout inflammatory response from previous workouts inhibits the anabolic signaling response from converting into a post-workout muscle protein synthesis rate elevation.
Stretching causes fatigue (measurable as reductions in maximum strength and late phase rate of force development) that is present for at least 20 minutes afterwards.
Static stretching is often considered to be a completely different type of intervention from strength training. Yet, it often causes increases in maximum strength, which suggests that there is more in common between the two types of exercise than is often assumed...
While the majority of research has focused on aspects of hamstrings strength and muscle architecture for preventing hamstrings strain injury, there is emerging evidence that the involvement of the synergist hip extensors during high-speed running may also play a role.
Exercises that are done earlier in a workout tend to produce greater hypertrophy for the targeted muscle, irrespective of whether those exercises are multi-joint or single-joint.
I don't think our current approaches to measuring volume accurately record the number of reps that provide a mechanical stimulus for the muscle fibers to grow. This way of measuring volume solves that problem.
Read more here:
Heavy load strength training with maximal efforts on each rep produces superior gains in maximum strength, rate of force development, and work economy in comparison with volume load-matched moderate load strength training with self-selected tempos.
Eccentric overload strength training (using a greater force in the eccentric phase) does not have the same effects as a slow eccentric tempo. One increases the level of motor unit recruitment, the other increases time under tension.
Fatigue after exercise is very complex, but that doesn't mean that we cannot simplify it by breaking it down into component parts. Here is my current mental model for understanding how various processes cause fatigue (= strength loss) during the post-workout period.
Contrary to the claims of some experts, central nervous system (CNS) fatigue can last for several days after a workout, especially when the workout causes a large amount of muscle damage (high volume or eccentric-only training)
Ballistic (explosive) strength training, often produces large improvements in the ability to produce force at high speeds (high-velocity strength), whereas heavy strength training often only achieves small increases. Why is this?
Traditionally, it has been suggested that post-workout stretching can help improve the rate of recovery after exercise. However, this meta-analysis showed that there is no such beneficial effect.
Stretching bouts cause delayed onset muscle soreness (DOMS) and elevations in indirect markers of muscle damage, in much the same way as strength training.
Central nervous system (CNS) fatigue is something that we ideally want to avoid during strength training, because it stops us from recruiting the highest threshold motor units, which are the ones that control the most responsive muscle fibers.
Time under tension is usually measured as the total time for which a muscular contraction is performed. Yet, this measurement is unrelated to hypertrophy. A far better measurement would be the time for which the high-threshold motor units are recruited.
Tendons adapt after strength training by increasing in stiffness and size. By looking at the different effects of different types of strength training, we can draw inferences about the stimuli that cause each individual adaptation.
We identify the amount of muscle mass that is lost (relative to the hypertrophy created by a single workout) between workouts by looking at the maintenance literature.
Heavy strength training ↓ maximum velocity while high-velocity movements increase it. Only ↑ in maximum velocity benefit sprint performance. Why would we use a training method that ↓ the key physical quality determining performance?
When trained with the same workout volume, some muscle groups take longer to recover the ability to produce force than others. This suggests that the best training frequency will differ substantially between muscle groups.
Many strength coaches make use of Olympic weightlifting exercises and their derivatives for improving athletic performance, but some research suggests a combined program of squats and loaded jumps may be better
Most detraining studies have shown that muscle mass is lost more quickly than strength. This study found that some of the strength gains achieved through training were retained even after 31 weeks of detraining. This likely reflects an increased ability to recruit motor units.
Cluster sets, drop sets, and rest pause training methods are very similar but yet also display important differences that likely affect the adaptations that may occur.
Here's a framework setting out the ways in which maximum concentric strength in an exercise (the 1RM) can increase, and how each way might transfer to force production in sporting movements
I wrote a detailed explanation here:
Hip extension exercises involve three independent muscle groups.
Each muscle group contributes differently to the torque at the hip, depending on squat depth and load.
Squats to different depths are not going to produce the same results.
Fatigue after concentric training may be caused mainly by metabolites, while fatigue after eccentric training may be caused mainlyby disruptions to excitation-contraction coupling and muscle damage.
High-velocity strength training, also often called "ballistic" or "explosive" strength training, produces very different adaptations from conventional, heavy strength training, which is why it preferentially increases the ability to produce force at high speeds.
The inverted row is a hugely underrated exercise, which is great for developing the upper back with less load on the lumbar spine. It can be progressed easily by using a weighted vest. I would much rather see it in a program than the more popular bent over row.
The stimulating rep model of hypertrophy explains [1] how training with a range of moderate and light loads causes the same hypertrophy despite different volume loads, and [2] why training with heavy loads produces less muscle growth than training with moderate or light loads
Many studies have now shown that the rectus femoris does not grow after squats, leg presses, or any other multi-joint lower body exercise. For complete quadriceps development, the knee extension is a necessary addition.
Whether a workout causes muscle damage or not affects whether muscle glycogen can easily be replenished afterwards. This means that overreaching blocks can lead to increasingly reduced levels of muscle glycogen.
Heavy strength training is not very effective for increasing maximum speed. To maximize speed gains after heavy strength training requires training in a very specific way.
Read more:
Tendons adapt to exercise, often by increasing in size and stiffness. However, the exact adaptations differ depending on the strength training variables employed.